Notice Board


Wednesday, August 9, 2017




Hot machining, Machining of Plastics, Unit heads, Plastics cooling, electro forming, Surface Cleaning and Surface Treatments, Surface Coatings, Paint Coating and Slushing, Adhesive Bonds, Adhesive Bond Joints, Adhesives, Surface Coating for Tooling, Graphite Mould Coating, Vacuum Mould Process.
Introduction, Types of Composites materials, Agglomerated Materials, Reinforced materials, Laminates, Surface Coated Materials, Production of Composite Structures, Fabrication of particulate composite Structures, Fabrication of reinforced Composite, Fabrication of Laminates, Machining, Cutting and Joining of Composites.

Introduction, Polymers, Polymerization, Addition of Polymers, Plastics, Types of plastics, Properties of Plastics, Processing of Thermoplastic Plastics, Injection Moulding, Extrusion Process, Sheet forming processes, Processing of Thermosetting Plastics, Compression Moulding, Transfer Moulding, Casting of Plastics, Machining of plastics, other processing methods of plastics.
Introduction, casting, thread chasing, Thread Rolling, Die Threading and Tapping, Thread Milling, Thread Measurement and Inspection
Theoretical basis of metal forming, classification of metal forming processes, cold forming, hot working, Warm working, Effect of variables on metal forming processes, Methods of analysis of manufacturing processes, Open Die forging, Rolling Power Rolling, Drawing, Extrusion. 

                                                      UNIT IV 
Introduction, Product Application, Limitation of Die Casting, Die Casting Machines, Molten metal Injection systems, Hot chamber machines, Cold chamber machines, Die casting Design, Design of Die casting Dies, Types of Die casting Dies, Die design, Die material, Die Manufacture, Die Lubrication and Coating, Preheating of Dies, Vacuum Die Casting, Recent trends In Die Casting Process.
Definition, Cost accounting or costing, Elements of costing, cost structures, Estimation of cost elements, Methods of estimating, Data requirements of cost estimating, Steps in making cost estimate, Chief factors in cost estimating, Numerical examples, calculation of machining times, Estimation of total unit time.




Hot machining, Machining of Plastics, Unit heads, Plastics cooling, electro forming, Surface Cleaning and Surface Treatments, Surface Coatings, Paint Coating and Slushing, Adhesive Bonds, Adhesive Bond Joints, Adhesives, Surface Coating for Tooling, Graphite Mould Coating, Vacuum Mould Process.
Introduction, Types of Composites materials, Agglomerated Materials, Reinforced materials, Laminates, Surface Coated Materials, Production of Composite Structures, Fabrication of particulate composite Structures, Fabrication of reinforced Composite, Fabrication of Laminates, Machining, Cutting and Joining of Composites.



 A considerable percentage of the parts of up-to-date machinery are made of heat resisting stainless steels, heat-resisting super alloys and similar materials. This is due to the increased production of machines operating at high loads, pressures, speed and temperatures, as well as in chemically active media.
The machining of work pieces of such materials, by conventional methods, is extremely difficult and many cases, impossible. Very low cutting speed and feeds will have to be employed, resulting in heavier loads on machine bearing and sides. Also, it will be quite a problem to correctly select cutting tool materials, tool life or tool geometry. Heat-resistant materials contain considerable amount of alloying elements, have a tendency to weld  onto the cutting tool, loose very little of their strength, even when heated to temperatures as high as 800oC, have a very high shear strength, combine high tensile strength with high toughness, are susceptible to considerable work-hardening and have low thermal conductivity. All these features lead to the development of high cutting forces, and temperature, and to intensive cutting tool wear. In addition, the surface finish obtained in machining is poor. Consequently, tools for machining heat- resistant materials should be very carefully sharpened and lapped. Tool geometry should be properly selected.
To overcome these problems, entirely new machining methods have been developed. Some of these : ECM, EDM and USM have already been discussed. The method of “Hot Machining” basically consists of applying localized heat, ahead of cutting tool, to reduce the shear strength of the work piece metal (thus improving its machinability), and to permit the easy formation of the cutting chip. The chip is usually produced in the form of a long smooth chip with lessened shock to the tool.
The application of correct amount of heat, in the required place, is of maximum importance. Hence, the type of heat and its application needs to be studied with care. Heating of the work piece also influences tool wear. Therefore, heating in the cutting process improves machinability; when the increase in tool life, due to the reduction of the work done in cutting, is greater than the detrimental effect of the high temperature on the tool, leading to increase wear. It has been established that the temperature – interval in machining with heating of the work piece should be taken 35 to 40oC lower than the temperature – interval for annealing and aging.
The heating temperature depends upon the cutting speed and the rate of feed, since the amount of heat generated in cutting increases with the speed and feed. Thus in truing a particular grade of stainless steel, heating temperature is:
> 500oC at cutting speed of 19m/min
= 350oC at cutting speed of 300m/min
= 230oC at cutting speed of 375m/min

1.      The process id economical and in many case has reduced the operating costs.
2.      Production gets increased.
3.  Good surface finish can be obtained, superior to that obtained on these materials at room temperature.
4.      Little evidences any adverse micro structural change.
1.1.1 Heating devices: The work piece can be heated by various methods of heating as high-frequency induction heating or electric – arc heating devices mounted on the carriage, by resistance heating with the application of an electric current in the cutting zone, by flame heating, by Plasma arc heating. Sometime, the blank is preheated in a furnace before being loaded into the machine tool.


 Basically a unit head is a power operated slide with provisions for advancing different types of cutting tools to the component. Unit heads are mounted on Standardized bases. A unit head consists of a cast iron body which houses the gears driven from the motor to rotate the spindle. The body has longitudinal movement along the base which is affected from the main motor through a lead screw and nut.

Fig 1.1 Unit Head

The idle motions are carried out with the help of a traverse motor and its electrical brake. Depths of cut and various intermittent motions are controlled by a series of trip stops secured to the head. While a dead stop can be used to ensure the accuracy of cutter depth. The longitudinal movement of the head can be actuated also through the rotation of a plate or cylindrical cam, or when required for arduous duties, by hydraulic power.
The “Unit Head” has opened up avenues of multiple- operation machines for the completion of components which would need a line of machine tools, each of which would need to be fully tooled and manned. Also inter stage handling and storage has been eliminated.
It is possible to load one or more components and not to remove them from the fixture on the machine until the completion of a wide range of operations. On the completion of the machining of these parts, the heads can be dismantled from the bases, and these with the bases, passed into stores until required for the machining of other components. The “Unit Heads” have made considerable headway in the production of medium to large- scale components.

1.      Unit heads allow for maximum versatility.
2.      They can be mounted and remounted in a variety of positions on standard interchangeable bases.
3.      High production rates, along with consistent high accuracy.
4.      Number of handling times reduced.
5.      Less floor space needed for machines and for spring.
6.      Operators more fully employed.
7.      Physical efforts of operators reduced.
8.      Good economical recovery rate.

The unit head is available in a wide range of sizes. Power rating of driving motors ranges from about 0.2kW to 22kW, with spindle speeds from 41 to 200 rev/min, and with feeds of 0.025 to 3.50 mm/ rev.
Each unit head needs a control panel and such panels can be housed in separate cabinets or enclosed within a standard base. When a machine setup includes several heads, a combined control board can be enclosed within the framework of the base.
The majority of the unit heads are designed for boring, broaching, chamfering, counter boring, countersinking, drilling, end milling, face milling, gage milling, reaming, and sawing, shot-facing, tapping, thread rolling and turning. The front faces of most of the heads are provided with means to allow the fixing of multiple-spindle drilling heads, to permit the drilling of more than one hole simultaneously. The versatility of drilling unit heads has been discussed under art. 


 Certain types of non-cutting tools are made nonmetallic materials including plastics. The most common materials are epoxide resins, because of their better mechanical properties (excellent properties when loaded in compression) than other plastic materials.
Epoxide resins are more costly than any other tool material. But they are lighter then other materials, being 1/4th weight of Zinc alloys and less than 1/4th weight of cast iron. Also the cost saving due to the reduction in time and labour involved in marking plastic tools outweighs the material cost. Other properties of plastics have been discussed. Reinforcing with fiberglass can increase their tensile strength.
Epoxide resins can be poured, cast, laminated or moulded into intricate shapes with negligible shrinkage and finish with a minimum amount of surface finishing. Consequently, the greatest saving in cost is obtained with tools of complex shape, for which the cost of machining and final finishing will be very high.
Compared with any of the tooling metals, plastics are soft and have a much shorter life than comparable tools in steel. It is not economical, therefore, to use plastic tools when: tool shapes are conventional, the component material is thick and quantities and large. Faulty handling too can damage plastic tools, more easily.

1.3.1 Applications:
Plastic tools are being used in many industries:
1.      For drilling jigs, routing jigs and fixtures for assembling, brazing and welding. In the majority of cases inserts are provided to prevent endure wear.
2.      In plastic industry for the production of moulds for both thermosetting and thermoplastic materials, for vacuum forming and for the injection blow moulding of polythene products.
3.      In foundries for the production of patterns and core boxes. The entry orifice of the latter is normally fitted with a hardened steel insert to counteract the abrasive affect of the blown sand.
4.      Metal forming tools for drop hammers, hammers blocks multipart press tools, piercing – punch plates, rubber press tools, spinning chucks and stretch press formers. Most of these tools can be given extra support by the inclusion in the mould of metal or fiber glass frames or supports.
5.      Plastic tool also offer many advantages where short runs and prototypes are required or where a set of tools is required very quickly.

General tapers and blending radii assist in producing a strong tool. The thickness of component metal should rarely exceed about 1.5 mm while radii less than 4.75 mm are to be avoided.
The metal formed by plastic tools includes:
Aluminum alloys, brass and other copper alloys, mild steel, nimonic, stainless steel and titanium.

1.3.2 Production of plastic tools: Plastic tools can be produced by two methods: by Casting and building up reinforced layers of resin and glass fiber. The casting process is used for the production of tools of large mass, such as forming dies and punches. Selected fillers are added to the resin to reduce the cost of the mass and provide the properties required in the tool. Inserts and supports can be embodied in the casting to provide strength where required. Casting is least time – consuming and the more reproducible of the two methods.


Plastic can be machined, but in most cases, machining of plastics is not required.  Moulding and forming methods can obtain acceptable surface quality and dimensional accuracy.  However, there are certain plastics like PTFE (Polytetra fluoroethylene) which are sintered products and are not mould able by usual techniques, as they do not melt. For such “thermo stable plastics” machining is a viable alternative to moulding.
The machining of plastics (by operation such as turning, drilling and milling) has special features due primarily to the structure of the material.  It also depends upon the binder upon the binder and the filler and the method of moulding the component. For example, the machining of thermosetting plastics allows optimum cutting variables and tool geometry to be employed because these do not soften on heating, whereas thermoplastic resins soften under heat. The permissible maximum temperature in the cutting zone is 160OC for thermo-setting resins and only 60OC to 100OC for thermoplastics.
Special features of the machining of plastics are:-
1. The tendency of certain plastics to splitting.
2. High elasticity (40 times as much as that of steels). Therefore, they must be carefully supported, to avoid their deflection during machining.
3. Non-homogeneous structure of the material, with components of different hardness. This results in poor surface finish after machining.
4. Plastics have a strong abrading action on cutting tools.
5. Their low thermal conductivity results in poor heat dissipation from the cutting zone and in over-heating of the cutting edges.
6. The intense dust formation, especially for thermosetting plastics, makes it necessary to use special dust -removing devices.
7. The hygroscopic of plastics excludes the use of liquid cutting fluids. Compressed air is commonly used for cooling.
8. Reinforced plastics are very difficult to machine.

Plastics can be machined with H.S.S. and cemented -carbide tools.  In machining a plastic material with a filler of glass, quartz or mica type, a satisfactory tool life can be obtained only with carbide -tipped tools.  Only diamond tools are suitable for turning high-strength plastics of this type.  The strength of cast parts of laminate plastics is 40 to 50 percent less than that of the parts made by compression moulding.   Therefore, higher cutting speeds and feeds can be used in their machining than for strong thermo-setting plastics.  The main trouble in turning laminated plastics is the peeling of the surface layer.
The cutting variables are also influenced by the life of cutting tool which is subject to abrasive wear in machining most engineering plastics.  Dulling of the cutting tool leads to a poor surface finish and to breaking out of the material at the points the cutting tools enters and leaves the cut. This makes it necessary to use more keenly sharpened cutting tools for plastics.  The need for sharp cutting edges follows from the high elasticity of plastics.
The selection of cutting variables is also influenced by the low heat conductivity of the plastics, since; in machining the tool may be within a closed volume (as in drilling) with no cooling facilities. This may lead to charring of the machined surface.
The cutting tool angles for machining plastics are made somewhat different than those of tools for ferrous and non-ferrous metals. The rake angles are positive and relatively larger.  Because of the visco elastic behavior of thermoplastics, some of the local elastic deformation is regained when the load is off.  Therefore tools must be made with large relief angles (200 to 300).
Abrasive machining of plastics has many advantages over machining with metal cutting tools. These include the absence of splitting and crack formation, and the better surface finish that can be obtained.
In grinding, the contact between the wheel and the surface being ground, should be as short as possible, to avoid burns.  Organic glass is commonly ground with coated abrasive, applying an ample amount of water as a coolant. If possible, however, grinding should be replaced by polishing with a felt, broadcloth or flannel wheel charged with lapping paste, the process is known as “Buffing”. The buffing wheels are of diameter 250 mm, 40 to 60 mm wide and of speed 2000 rev/min.  Medium and fine lapping pastes are used as the buffing compound for plastics. Laminate fabric base, asbestos-fiber and glass -fiber laminate can be cut with abrasive wheels (SiC) of grain size 24 to 46 and with a 5% emulsion as the cooling fluid.


Electro-forming is a process of precision metal parts that are usually thin in section, by electro-deposition on to a form which is shaped exactly to the interior form of the product & which is subsequently removed
In the process, a slab or plate of the material of the product is immersed into electrolyte & is connected to the positive terminal of a low voltage, high current d.c power. So it becomes an anode. A correctly prepared mandrel or a pattern of correct shape & size is immersed at some distance from the anode &is connected to the negative terminal. The mandrels are made from variety of materials both metallic & non-metallic. If the material is non-conducting, a conductive coating must first be applied to perform electroplating. The mandrel should poses mirror like finish. When the circuit are closed metal ion are removed from the anode, transported from the electrolyte towards the cathode and deposited there. After the deposition the master is removed or destroyed.  A metal shell is confirms exactly the masters. It may take hours or day to deposit of sufficient thickness. The thickness of electroforms ranges from0.25-25 mm. The processes very much simple electroplating with the diff. That where is the electroplating, the deposit stays in place (on the cathode), in electroforming, it is stripped from the form, the electroformed products are typically from nickel, iron, copper, and more recently from copper-tin, nickel, cobalt and nickel,

1.5.1 Advantages:
1.      Low plant cost, cheap tooling & absence of heavy equipment 
2.      Low labor operating cost
3.    The process can be designed to operate continuously throughout day and night
4.    Electro deposition can produce good dens deposit, and compared with casting, electroforming offers high purity, freedom from porosity with the homogeneous structure these important quality are seldom obtained to such a degree in machine parts, stamping or forging
5. There is no restriction the internal complexity of electro-forms and this advantage eliminates in many instances, the costly joining processes.
6.     The process has no equal for the reproduction of fine or complex details
7.    The use of inserts has widened the application of the process. Metal inserts are attached to or are embedded in a wax or fusible alloy master, &, when the master is melted, the inserts remain attached to the electro-form.
8.      A high quality surface finish is both obtained on interior &external surfaces of the electro forms. Accuracies as close as .005 mm
9. complex thin –walled parts can be produced with improved electrical properties
10.  Shell-like parts can be produced
11.  Quickly &economically

1.5.2. Mandrels:

The mandrels, the mould or the matter, is the most expensive item in the process of electro-forming. Mandrels can be made of several metallic &non-metallic materials the metallic materials are aluminum, brass, and carbon steel. a common feature of these mandrels  is their oxide formation film –which facilitates their separation from electro form with out any surface treatment.
Depending on shape of electro –form mandrels are of three types-permanent; semi permanent & expandable Permanent mandrels
 These mandrels are usually made of metals or glass or rigid plastics .the surface of non-metallic mandrels is made conductive by metalizing by electro-forming or a chemical deposition technique. For close tolerances work such as gear &gauges, stainless steel is recommended. Such materials can be used indefinitely, with a minimum treatment to preserve the smooth surface. Adhesion is minimized by the application of thin coating of a parting compound  Semi-permanent mandrels
for straight sided components  or components which have several cuts up to about .013 mm, semi permanents mandrels are used .these are made of steel with fusible coating, compounded usually made from wax &graphite .,to remove electro-form the fusible layer is melted &after removal , mandrels is cleared & rebuilt Expendable mandrels
For complex electro-form are made from
(1) Plaster, which after electro-forming are removed by breaking.
(2) Plastic resins &fusible alloys which are melted.
(3) Aluminum & zinc which are dissolved chemically
(4) Brass
Plastic resins are commonly used for decorative work where tolerances are wide without undercuts. The surface finish of mandrels made from fusible metal alloys can be removed by electroplating a layer of copper .025 to .050 this copper layer is dissolved from electroform after fusible alloy is melted

1.5.3 Applications
1.      Moulds & dies feature high in the list. Moulds for the production of artificial teeth rubber 7 glass products, & high strength thermosetting plastics are now commonplace. The moulds can be made with undulating parting lines which have made a considerable impact upon the production of thermoplastic toys & novelties.
2.      Radar 7 electronic industries –radar wave-guides, probes, complicated grids screens 7 meshes can be produced easily
3.      Spline, thread & other types of form gauges
4.      Cathode for e c m & electrodes for E D M
5.      Electro-formed core boxes with inbuilt heating elements.
6.     Electro-formed precision tubing, parallel & tapered formed to different shapes to eliminate the need for bending which the bore.
7.      Electrotypes floats bellows, venturi tubes, fountain pen caps, reflectors, heat exchanger parts honey comb sandwich, parts for gas appliances 7 musical instruments, radio parts , filter & dies .

1.5.4 Electro-Forming Is Particularly Used For:

1.      High cost metals
2.      Low production quantities
3.      Quantity of identical parts, for example a multi –impression mould
4.      The possibility of using a single master for production of a number of electro-forms
5.    Where as intricate female impression is required, son that it would be much easier to produce a male form


During the manufacture of virtually all metal; parts, filling, fine metal chips , pieces of chips , remnants of wastage or abrasive grit may get into holes or channels of parts . Also oil, dirt, grease, scale, and other foreign materials remain affected to the main part surface the purpose of surface cleaning &getting rid of all above materials is two fold – firstly they may get into holes or channels of part. Subsequently, in operation finished goods they may be carried by lubricants into the bearings, where they may lead to overheating & premature wear of the bearing & even to breakdown of the whole machine. This can be properly avoided by cleaning. Thorough cleaning of parts is essential for high quality of their performance.

The second purpose of surface cleaning is to prevent corrosion, & to combine a decorative appearance with protective coating. All metals will oxide & corrode, when expose to certain environments, unless protected with an air thrust. Before application of any protective coating, it is essential that the surfaces of the part be prepared by proper cleaning to good adhesion. Various surface cleaning methods are:

1.6.1 CHEMICAL CLEANING METHODS Alkaline Cleaning: In this method dipping them in aqueous solution of alkaline silicates, caustic soda, or similar cleaning agents cleans parts. Some type of soap is added to aid in emulsification. Wetting may be added to the solution to help in thorough cleaning of the parts. The method satisfactorily removes grease &oil. The cleaning action is by emulsification of oils & grease. Special washing machines are employed in lot &mass production. Washing m/c may be of single, two or three chambers types.

(a) In a single chamber washing m/c, washing chamber is equipped with a bank of pipes with nozzles. A pump delivers the cleaning fluid, drawn up from main tank to the pipes. The nozzles are arranged so that the part or unit is washed from all sides simultaneously with powerful streams of fluid. The parts may be transferred in washing machine by chain conyver. The cleaning fluid is heated by a steam coil of 60 to 80, & therefore parts ejected from the machine dry fairly soon.

(b) A two-chamber washing machine has two washing chambers. The parts are cleaned in first chamber & then rinsed of washing solution in the second chamber.

(c) In three –chamber machines third chamber is used for drying. Solvent Cleaning: Small parts are cleaned of oils, dirt, grease, and fats by dipping in commercial organic solvents, such as naphtha, acetone, carbon tetra chloride. The parts are then rinsed once or twice in a clean solution of same solvent. The vapors of these solvents are toxic & therefore require ventilation. The method is particularly suitable for aluminum, brass, lead, which are chemically active & might get attacked by alkaline cleaners Emulsion Cleaning: In this method of cleaning, the action of organic solvent is combined with that of an emulsifying agent. The solvent is of generally of petroleum origin & emulsifying agent, which are soap or a mixture of soap & kerosene oil, include nonionic polyesters, high molecular weight sodium, amine salts of alkyl aryl sulphonetes, acid esters of polyglycerides, glycerols & polyalcohols. Cleaning is done either by spraying or dipping the metal parts in solution & then rinse & drying. The method is suitable for parts & aluminium, lead or zinc while are attached by alkaline solution Vapor Degreasing: Vapor Degreasing is a similar process, except that the solvent vapors are used as the cleaning agent. The solvent is heated to its boiling point and the parts to9 be cleaned, are hung in its vapors. The vapor condenses on the surface of the parts wash off the oil and grease. Pickling: The process is used to remove dust or oxide scale from surface of components. The parts are filled in a tank filled with an acid solution, which is 10 to 12% of sulphuric acid in water, & is at temp from 65 to 85 C. the solution acts to loosen the hard scale from the components surface & removes it. The acid solution should not react with metal while from the scale. For this an inhibitor agent is added to9 the solution. Pickling process only removes oxide scale. Ultra- Sonic Cleaning: Very dirty small parts, especially those of intricate shape with hard-to-access inside surfaces, are difficult to clean in ordinary washing facilitates. Such parts are cleaned much more efficiently by ultra sonic cleaning method. The method is effected in three stages – prelimary, ultrasonic, & rinsing of parts in a clean washing medium (kerosene, trichloroethylene) 
Ultrasonic energy is produced by a high frequency generator, which feeds high frequency electric energy to transducers that transforms electric energy into inaudible sound energy. The transducers are fixed to the bottom or the sides of a stainless steel tank designed to afford the optimum acoustic conditions. High velocities are imparted to particles of cleaning liquid in the tank. Cavitations bubbles of microscopic dimensions are formed on the surface of the components. The cleaning action is done by formation of bubbles, which practically blast all contaminants from all types of components in seconds, penetrating every crack or crevice & removing all loose parts. The cleaning liquid includes water, water based solutions, mild acid  & caustic soda, which are thermostatically controlled to operate at temp of about 45 C. The effectiveness of this method is 99%.   
Rinses are required in all cases to ensure through removal of cleaning agent before coating. After being washed, machines parts are dried carefully. This is done by compressed air. ADVANTAGES

1.      The process can be manned easily by trained labour.
2.      The process reduces the time element.
3.      The process produces cleaner surfaces & eliminates many manual operations & the quality hazards.
4.      The cleaning of intricate assemblies after final assembly can reduce testing time. APPLICATIONS

The process can be used in all types of engineering factories, cafes, dairies, hospitals, & hotels & by manufacturing jewellery. Components, which have been cleaned by the process, include – ceramics, cutlery, electronic equipment, machine tool equipment, watch parts.
Other components, which need to be scrupulously cleaned, include air craft, ball race assemblies, engine components, fuel gauges, gas turbines, gears, glass components, hydraulic devices, jet engine parts, refrigerator parts, satellite components, & parts for semi conductors, teliprinters parts. Surface Polishing: Mechanical polishing of pressed or extruded metal products & many such articles is by using a wide range of wire brushes or mops, in conjunction with specially blended greases & oils the two non –mechanical techniques are chemical polishing  & electrolyte polishing. Chemical polishing has made greater advantages due to increased use of aluminum for a variety of applications. Electrolyte polishing has made less progress, because it is more expensive to install.

(a) Chemical Polishing

In the process, the metallic objects are immersed in bathtubs of selected acids. During process certain amount of metal; mainly peaks are dissolved, producing a bright surface with out the formation of etched pattern. For chemical polishing of aluminum alloys the most successful of the solution used contain phosphoric, nitric acid, sulphuric acids. Production cycle consist of following steps
(1) Immerse for 1 to 3 min at 100 C.                                                 
(2) Remove & rinse in hit water to remove the viscous film formation.
(3) Rinse in a mixture containing equal amount of water & I, 42 sp. Gr. Nitric acid at Room Temperature
(4) If anodizing required, rinse in cold water.
(5) If lacquering is called for, rinse in cold water

The resultant surface finish is of order of .45 to .50 with a high reflection factor of 88%. ADVANTAGES

1.      The process is comparatively cheap, with low operating cost
2.      The equipment has along life.
3.      It is very suitable for delicate, thin –walled, embossed.
4.      Both the inside & outside surfaces are cleaned easily
5.      The process can be combined with barrel – polishing to reduce time & cost.
6.      The process can be included in aluminum anodizing cycle
7.      Improved reflectivity usually is obtained. 

(b) Electrolyte Polishing

 The principle of electrolyte polishing is the same as that of ECM. a surface layer of the work piece is removed by anodic dissolution of the metal , leaving the component with a highly polished surface . This depleting process is known as ELECTROLYTE POLISHING

When a metallic component is immersed in electro polishing electrolyte, the current line leads from surface peaks, tangentially, causing a higher current density on the peaks than on valleys. Thus greater metal dissolution takes place on peaks to take smoother surface than on valleys. This viscous film protects the micro valleys from the action of current but permits minute peaks to dissolve. The rate of metal removal is 3 to 10 microns.

A wide range of metals & alloys can be electro typically polished, but the main industrial uses of the process are for polishing of alloys & stainless steel, copper alloys, nickel, & aluminum alloys.

1.7 CLEANING AND FINISHING OF FORGINGS                            

1) Removal of oxide scales: A thin layer of scale which is caused by contact of heated steel with air is formed on surface of steel forgings. Amount of scale depends upon the forging temperature & length & time of operation. The simple way to remove the scale is by employing steam or compressed to blow away the scale.

2) Cleaning by pickling: Process is used to remove hard scale from surface of forging. It consists of immersing the forgings in a tank filled with an acid solution, which is 12 to 15 % concentrate of sulphuric acid in water. The acid solution should not react with clean metal while removing the scale. For this an inhibitor is added to solution.     

3) Tumbling process: Process is used to remove the scale & for general cleaning of the forgings. The forging along with abrasive materials such as coarse sand or small particle is placed in barrel. The tilted barrel is rotated at low speed s. the forging & abrasive roll over themselves. This action loses the scale from surface of forging & removes it along with affecting a general cleaning of forging.

4) Blast cleaning:       Process consists of directing a jet of sand, grit or metallic shots against the forging. The blast force is obtained from compressed air or centrifugal force through suitably designed apparatus. This process removes the scale & a smooth surface finish is imparted to the forging.                                                                                                                                                                       
1.7.1 CLEANING AND FINISHING OF CASTING                                     

After casting is solidified & cooled down sufficiently in an expandable mould, the first is freezing the casting from mould. The operation is called as “SHAKE OUT OPERATION” since a great deal of heat & dust are involved in this operation, the operation is usually mechanized. Shake out is usually done by means of vibratory knockouts, jolting grids & vibrators. The mould is intensively jolted & broken up. After shaking the casting out of mould, it is conveyed to the fettling shop for cleaning and finishing. The process consists of following operations – core removal, cleaning of surfaces, and removal of gates, risers & fins.               

1) CORE REMOVAL OR CORE KNOCKOUT: This operation is also done manually. Hampering & vibrations will loosen & breaks up cores. Stationary 7 portable vibrators are employed for this purpose. To knockout from heavy engines, it is disadvantages to use air drills. Removal of cores by hydro blasting is more sanitary process keeping in view dust problems. The operation consists of breaking up & washing out the cores with a jet of water delivered at a pressure of 25 to 100 mm.       

2) CLEANING OF SURFACES: The process involves the removal of all adhering sand &oxide layer & produces a uniformly smooth surface. Mechanical methods are employed for this purpose, since cleaning by hand with wire brush is tedious & costly.

I) Tumbling: This method is used for cleaning & light casting. The Castings are loaded into a tumbler or barrel along with white iron picks. Rotation of barrel causes casting & jack stars to tumble. Jack stars abrade the surface of casting &also abrade surface of one another. This operation removes adhered sand & oxide scale from the surface of the casting. The rotational speed of barrel is 30 rev/min.                                                                                                                

Ii) Sand Blasting and Shot-Blasting: This method is widely used to clean surfaces of light, medium & heavy castings. In these machines, dry sands or shots is blown by stream of compressed air against the surfaces of casting. The impact of abrasive particles traveling at a high speed, on the surface removes adhering sand & oxide layer. Velocity of abrasive particles leaving the nozzle of m/c ranges from 35 to 75 m/s & pressure 0.7 MPA

iii) Airless Shot Blasting: In this shots are hurled on the surface of casting by a fast rotating paddle. For harder castings, the shots are made up of white iron, steel, whereas for softer non ferrous castings, these are made up of copper, bronze, glass or mild iron,. The wheel rotates at 1800 to 2500 rev /min. The velocity of shots striking the surface is about 60 to 72 m /s.                                                                                                                                                 
Iv)Hydro Blasting: This is most effective surface cleaning method. Here two operations are accomplished simultaneously –core knockout & surface cleaning. Casting are placed on a rotary & stationary table & high velocity jets containing about  15% sand & 85 % water under a pressure of 10 to 20 mpa . The jet velocity can be up to 100 m/s.                                                                                                                                                                         
v) Removal of Gates and Risers: Gates, runners, risers, and spure can be removed before or after cleaning operations. In brittle materials, these are simply broken off from the castings. in more ductile materials , following the following methods are used to remove them –power hacksaws , band saws , disk type cutting edges , abrasive cut of edges , flame cutting with an oxyacetylene cutting torch & arc cutting for heat resistant steels which are not amiable to gas cutting.                                                                                                                                 
vi) Powder Cutting: Process by which risers & gates can be easily removed from castings made of oxidation resistant alloys. Preheated iron powder is introduced in oxygen stream. This burning iron then attacks the metal riser by a process of fluxing & oxidation.                                                                 

vii) Some minor defects defected may sometimes be repaired by welding without affecting the function of finished castings.  

viii) Finished castings are subjected to various heat treatments to modify mechanical properties or reduce residual stress.                   


The various surface coating on machine parts are used for protective, decorative, wear resistant and processing purpose. The different types of surface coatings used for this purpose are: metallic coatings, phosphate coatings, oxide coatings and plastic coatings etc.

1. Electro – deposited coatings: This process of coating also known as “electroplating”, comprises preparation of the surface to the plated, plating itself, and degreasing of the surface. The part to be electro-plated is made the cathode and the metal to be deposited is made the anode and both are placed in a tank containing an electrolyte. The process is carried out at a voltage of 10 V (D.C.) and current density of upto 10A/dm². When the circuit is closed, metallic ions from the anode migrate to the cathode and get deposited there. Some characteristic of electrodeposited coatings as given below:

a) Copper plating: Used for masking of steel parts from carbonization a case of hardening heat treatment, plating for improved running- in of plated surfaces as an under layer for multi-layer coatings. Coating thickness: 5 to 25µm.

b) Chrome plating: Wear – resistant protective and decorative coating. It result in improved retention of lubricant and lower co-efficient of friction. Coating thickness: 30 – 40µm.

c) Cadmium plating: Coating for protection against corrosion of steel in moist atmosphere (marine corrosion) and for improved running in of mating surfaces. Plating thickness: 15 µm.

d) Nickel plating: Undercoat of chrome, corrosion protection for steel, wear qualities and for decoration. Plating thickness: upto 25µm.

e) Lead plating: Resistance to chemical corrosion.

f) Zinc plating: Low- cost protection of steel and iron against atmosphere corrosion and fro decoration. Plating thickness: upto 15µm.

g) Silver plating: Electrical contacts. Good anti galling and seizing qualities at high temperature. Plating thickness: 2.5 to 12.5µm.

h) Tin plating: Coating for protection against weak acidic media, non-toxic protection in food, for subsequent soldering and for masking in nitriding. Plating thickness: 3 to 12µm.

i) Gold plating: Infrared reflectors, electrical contacts, jewellery.

j) Borating: High hardness coating.

k) Lead-indium plating: Electro-deposit of lead on a silver plated surface followed by indium plating forms a satisfactory bearing surface.

l) Phosphating: Anti-corrosive coating. Plating thickness: 0.5 - 1µm.

m) Brass plating: Brass plating is frequently used as a base for bonding rubber and rubber like materials to the metal. It improves appearance, provides soldering surface, which is abrasive resistant. Since brass tarnishes (it is satin yellow to bronze initially and when turns to black to green on exposure), it must be covered with lacquer, when used for decorative purposes. Brass plating is used on steel, zinc aluminium, and copper plate.
1 8.1 Electro-less plating: The method of plating differs from the conventional method of plating that is electro-plating, in that no external source of electricity is used in the process. The plating is obtained with the help of chemical reaction. For example, for nickel plating, a metallic salt of nickel, nickel chloride is reduced with the reducing agent, such as sodium hypophosphate. Nickel metal so obtained is deposited on the work piece. Nickels are two most commonly used metal, for this process. Advantages:

1.      This process can be used for plating non-conducting materials such as plastic and ceramics.
2.      This process does not produce hydrogen embitterment.
3.      Cavities, recesses and inner surface of tubes can be plated successfully.
4.      The coating has excellent wear and corrosion as compared to electro-plating. Disadvantages

The process is costlier as compared to electro-plating. Some times; some portions of the base of a work piece are not to be electro-plated for decorative purpose or for the sake of economy. This is known as “blacking out”. For this the complete base is prepared for electro-plating. The base is heated to 100ºc. Paraffin wax is applied to the portion to be black out and then the work piece is completely cooled. After that the electro-plating is carried out.
 Electro-plated parts are usually dull and posses little or no metallic luster. To provide finish, shine and luster to the electro-plated parts, mops and “compos” finish them. The mop should be moved slowly over the surface to avoid removal of any portion of electro-plated layer, the final finish/colors be obtained by mopping with chalk. Compos, which contain abrasive, should not be used with soft metals.

1.8.2. Phosphate coating: A coating for steel as a preparation for painting, adhesive bonding or rust proofing. The process involves the chemical development of a film, which contains ferrous insoluble phosphate of manganese and ferrum, or ferrum and zinc, by treatment with a dilute acid phosphate solution. Depending on the phosphate structure and the method of surface preparation, the phosphate film may be from 2 to 15 µm thick. A rapid phosphating process is known as “bonderizing”. Phosphate coating can also be used for non-ferrous and light metals.

1.8.3. Oxide coating: Oxide coating of steel parts is done for decoration, rust proofing and to obtain low friction surface. The coating is obtained by thermal, chemical and electro-chemical methods.
The thermal method involves heating the part in air, steam or molten nitre. An oxide film 1µm thick is formed on the part surface: the film color varies with the process temperature. Heating in the air serves to form thin oxide films on electrical components.
The chemical methods include alkaline and acidic oxidation. In the first method steel parts are treated with a hot concentrated solution of caustic alkali containing oxidants. In the second method, solution contains ortho-phosphoric acid and oxidants. The acidic oxidation is much quicker as compared to alkaline oxidation and provides a stronger oxide film with improved corrosion resistance. The oxide films on steel parts are (0.8 - 3µm) and porous, and therefore do not reliably protect the parts from corrosion. Their corrosion – resistance can be increased by subsequent varnishing.
The chemical methods are used to oxidant parts made of aluminium, manganese copper, zinc and their alloy. The field of the process application is the manufacture of instruments, tools and consumer goods.
Electro-chemical oxidation of the parts is made of ferrous and non-ferrous metals and alloy is carried out in solutions of caustic alkali. The parts being processed form an anode. The process runs at lower temperature and requires less chemical agents than the chemical alkaline oxidation. Prior to treatments of parts, these are cleaned of corrosion spots and degreased, and after oxidation they are rinsed in water. Decorative oxidation takes from 30 to 40 min; corrosion – resistant films require upto 1.5 – 2 hours for their formation.

1.8.4. The coating of nickel – cobalt, zinc- cadmium and tin – lead is obtained by methods, which are called “thermo electro- plating” or “thermo-diffusion”. The latter consists in that individual metals are successively deposited on the parts and in the course of subsequent heating these diffuse and form plating of some alloy. Nickel – cobalt plating increases hardness, zinc-cadmium plating upgrades corrosion resistance and tin-lead plating reduces porosity and improves appearance.

1.8.5. Plastic coating: Plastic is used as decorative, anti-corrosive, and anti-friction coatings. These are applied in liquid and powder form. The primary materials used are thermo-plastics such as: polyethylene, polypropylene, polyamide, polyvinyl butyral, polyurethane, fluroplastic and caprolactum etc. these are used in form of fine powders which on heating. Change to plastic state. The coast thickness ranges from 0.15 to 0.35 mm. before coating the parts are heated to 180- 300ºc depending on the plastic to be used. The treatment itself lasts from 2 to 5 s. plastic coating makes it possible to use carbon steels or non-ferrous metals.

1.8.6. Metallization: Metallization means spraying molten metal with the aid to compressed air. The metal particle moving at a speed of 100 to 150m/s strike the surface of a part being coated and adhere to it, thus forming a layer of strong, finely porous metal coating. The layer has a fairly high compressive strength, even though it is brittle. The coating thickness varies from a few hundredths of an mm to 3-4 mm. parts after being coated can be turned and ground. The method is used to obtain decorative, protective, antifriction and heat-resistant coatings, to restore worn out parts and correct defects of castings. The metal being sprayed is melted OA flame (gas metallization) or by electric arc (electro-metallization). The initial material is metal wire. Sometimes uses are made of equipment operating on metable powders. The surface to be coated is cleaned of oil and oxides. Sand blasting and rough turning is employed for better adhesion of the metal being sprayed to the surface.

1.8.7. Anodizing: Anodizing or anodic coating is a process of providing corrosion resistant and decorative films on metals, particularly aluminium. The process is the reverse of electro-plating, in that the part to be coated is made anode, instead of cathode, as in electro-plating. When the circuit is closed, a layer of aluminium oxide is formed on the anode (aluminium) by the reaction of aluminium with the electrolyte. The layer of aluminium oxide on the surface is highly protective.
There are two process used for anodizing.

1.8.8) Chromic acid process: In this process, 3% solution of chromic acid is made as the electrolyte at a temperature of about 38ºC. This process is applicable only to those aluminium alloys containg not more than 5% copper or a total alloy content of more than 7½%. The process produces a light yellow colour.

1.8.9) Sulphuric acid process: The electrolyte is 15 to 25% solution of sulphuric acid. The process is applicable to aluminium alloys containg more than 5% copper or a total alloy content of more than 7½%. The process produces a light yellow colour. This process shall not be applied to parts having joints or recesses in which solution may be retained. Normal anodized coatings are 0.0050 to 0.0075 mm thick.
1.8.10) Hot- dip coatings: Many metal parts are used for making food containers due to the non-toxity of tin. To remove the excess tin, the sheets are passed through rollers after these come out of the bath.

(i) Zinc coating: Giving a coating of zinc is called “Galvanizing”. One method of doing so is by “electro-plating”. In the hot dip method, the parts or steel sheets are fluxed by immersing them into a solution of zinc chloride and hydrochloric acid. After that they are dipped into a molten zinc bath. Again, to remove excess zinc, the sheets are passed through rollers after they leave the bath. Galvanized steel sheets (and more recently, also one sided galvanized sheet) find increased use in automotive and appliance industry in addition to their use for roofing.
(ii) Lead coating: Load- coated sheet provides anticorrosion properties in some media. Where tin coated and zinc coated sheets can not resist corrosion. However, lead coated sheets cannot be used for food applications, because lead is toxic. An alloy of 15% to 20% tin and the remaining lead can also be used for this coating. Lead coating method is also called “terne” coating.

(iii) Aluminum-coating: Aluminum – coated sheets can resist corrosion by hot gases. Due to this, these are suitable for heat exchanges, automotive exhaust systems and grill parts etc.
1.8.11. Conversion coatings: These are the coating produced when a film is deposited on the base material as a result of chemical or electro-chemical reaction. Many metals particularly steel, aluminium and zinc can be conversion coated. The coatings can be phosphate coatings, chromate coatings oxalate coatings. After degreasing and cleaning in alkali, the part is soaked in suitable acid bath, for example, for chromate coatings, in chromic acid bath.
Conversion coatings are obtained for corrosion protection, prepainting and decorative finish. Another important application of this coating is as a lubricant carrier in cold forming operations, such as wire drawing.
Oxides that form naturally on the surface of metals are a form of conversion coating. Oxide coatings discussed above and also “anodic coatings” fall under the category of “conversion coatings”.

Bicycle wheel rim plating plant process chart
The rims are loaded on the fixture. The fixture can carry upto twenty rims at a time and after the loading is done, the robot is switched on which takes control of the whole process. The rims undergo various processes before being unloaded for use in body assembly shop. The various process of electroplating of the rims is as in the table below:

Table 1.1 Various process of electroplating

S. No.
Process sequence
Chemical concentration
(Deg. Celsius)
(Deg. Be)










Kerosene oil cleaning
Abrasive cleaning
Water rinse
Soak cleaning
Water rinse
Electro cleaning
Water rinse
Acid dipping
Water rinse (1)
Electro cleaning
Water rinse (ii)
Acid dip
Water rinse (ii)
Acid dip
Water rinse (ii)

Semi-bright Ni plating(ii)
Tri-Nickel plating
Bright Nickel plating
Drag out
Water rinse (iii)

Chrome plating

Drag out
Drag out
Water rinse (iv)
Unloading of the rim
M.T.kerosene oil 100%

NAON-80-100-80 ltr
Running water
Steelex 80-10gm/ltr
Running water
Ginbond- 808
Running water
HCI 30-40%
Running water
Ginbond- 808
Running water
Sulphuric acid 10-15%
Running water

Nickel sulphate
Nickel sulphate
Nickel sulphate
D.M.water tank
Running water

Chromic acid
D.M.water tank
D.M.water tank
Running water























Once daily

 Once daily

Once daily
Once daily

Once daily
Once daily

Once daily

Once daily

Once daily

Once daily

Once daily

Once daily

Once daily
Once daily

Nickel plating: is done as a protective coating as it has excellent adhesive properties which form good base fro chrome plating.
Chrome plating is corrosion resistant and also enhances the looks of the component. 


Metals parts are painted to protect their surfaces against corrosive action of surrounded medium & also to improve their appearance. The process of coating with paints & varnishes is carried out on 3 stages:      
1.      Preparation of the surface to be coated.
2.      Painting.
3.      Drying with finishing.
Preparation for painting consists in cleaning & degreasing surfaces. The surface so prepared is then primed for better adhesion of the subsequently deposited coating. Use is made of oil varnish, oleo vituminous, water-soluble & nitro soluble primers. The prime surface is then trited with a filter, whose layer should be as thin as possible. Oil varnish filters & quick drawing proxylin filter are commonly used. The clearance surfaces are painted & the preparation for painting consists in cleaning and degreasing the surfaces, priming, luting, and smoothing down the luted surfaces with emery clothe.


Following are the methods of industrial painting:

a) Brush painting: the brush painting is used in piece & small lot production. It is done by hand & is slow cumbersome method, where quick drawing paints are used. The method requires minimum of eq. But max. Of labour. The point losses are upto 5%.

b) Spray painting: The method consists in applying fluid paint in the atomized form. This method is the most common & productive, but requires premises equipped with exhaust devices & spraying eq. There are various ways of painting:

i) Mechanical spraying: in this method paint is delivered to spray gun by pump.

ii) Air spraying:  the paint I sprayed by jet of compressed air, which carries the paint mist to the surface being painted. The method is capable of coating 30-80 mt sq. Of surface/hour but losses is high 40-50%.

iii) Airless spraying: in this method paint heated to 70-90C IS FORCED through a nozzle at pressure of 2-4 n/mm sq. the production rate can be 50-200mtsq. Of surface/hour & paint losses are amt. to 25-50%.

iv) Electrostatic spraying: in this method a negative charge delivers paint, which gets on to the surface of charge metal part being painted. The charging is provided by high voltage const. current source. Setting up metal screens behind the parts can also use the method for non-metallic parts. The paint losses are less than 5%. The method makes it possible to improve working condition to provide for fairly high productivity.

c) Dip coating: this coating is used in automatic production. The method consists in dipping the parts suspended from chain conveyor, in bathtub. The method is used in large lot and mass prod. For painting parts of simple shape. The paint losses are 5%.


Adhesive joints can be made by applying adhesive in thin layer b/w the connected parts. They are fastening metallic as well as non-metallic (textile laminate, foam plastic) materials. ADVANTAGE: -
(1)  Reliable connection of parts made of very thin sheet materials.
(2)  Dissimilar metal can be joining.
(3)  The process is used to reduce production cost
(4)  It ism used to lessen the mass of parts.
(5)  Highly skilled labor is not required to bonding.
(6)  The process provides for tight and corrosion free joints.
(7)  Smooth bonded surface.
(8)  Exterior surface remain smooth.
(9)   Only low temp are involved so absence of stress or their lower concentration.
(10)   Heat sensitive material can be joined easily without any damage.
(11)   Complex assemblies can be at low cost.
(12)   Adhesive contribute towards the shock absorption and vibration.
(13)   It can tolerate the thermal stress of different expansion and contraction.
(14)     Because the adhesive bonds the entire joint area, good load distribution and fatigue resistance are obtained.
(15)   The joints are sufficiently strong in shear and with stand with dynamic and variable load.
(16)   Compared to welded soldered and riveted joints, adhesive bonded parts have uniform spread stresses and do not tend to warp.
(17)   The process is very fast. DISADVANTAGE: -

 1.      Comparatively low operational temp. (Maximum up to 100c fort most adhesive).
2.      Low resistance to tear off.
3.      Reduce strength of some adhesive in the course of timing (ageing).
4.      Tendency to creep, if subjected to long-standing and heavy load.
5.      The need of extended polymerization time. APPLICATION: -

Adhesive have particular develop in air –craft industry: the appearance of honeycomb structure is due to this method. The method is used in uncritical structure such ask control surface in aircraft body. In machine tools, adhesive are employed to bond carriage-guide –ways to beds, and in automobile industries to fasten the friction lining to clutch- disk brake –bands. Adhesive bonds are also used in appliance and c consumer goods fields and also sealing, vibration damping and insulating etc.


Adhesive-bonding of is affected on following types of surfaces:-

(1)   In cylindrical type of surfaces, for example, placing bushings into the holes in the housing –types and parts discs onto the shafts, coupling pipes together, fitting plugs and fastening lining to brake blocks.
(2)   On flat surface, for example, lap-type joining of sheet parts with one or two straps and so on.

Typical adhesive bonded joints are shown in figure: -

Fig. 1.2 Main type of adhesive bonded joint

The strength of joints is dependent on the amount of clearance it which is normally kept at 0.05 to1.5mm.with increased clearance the strength of joints decreases, as the length of overlapping is increases the force need to break down teethe joints increases asymptotically approaching a certain limit. Surface rough ewes of the parts bonded should be held to within 6.3 to 1micro meter. Increase in curing time has a favorable effect on the strength of adhesive-bonded joints.  With cold curing the strength grows continuously over a long period of time, the strength of bonded with old curing adhesive increases if the polymer process is accompanied by heating. Heating also greatly reduces the curing time. Making an Adhesive Bonded joints

An adhesive-bonding process comprises the following steps:
(1) Preparation of part surfaces.
(2) Preparation and application of the adhesive. 
(3) Assembly of parts under a pressure of determined by the grade of adhesive.
(4) Heating of assembly product.

Fig. 1.3 Hand Pneumatic Injector

The surface to be bonded must be cleaned and degreased. Cleaning is done with wiping wastes, brushes or in sand blaster. The substance used for degreasing is: acetone, trichloroethylene, carbon tetra chloride and other organic solvents. Aluminum alloys parts are prepared by pickling, where necessary the surface to be joined is machined to obtain a surface finish to provide a better holding if the adhesive.
Adhesive are prepared in special polychloroethylene or metallic containers; the will be chrome plated or varnish with silicone. Hot curing adhesive can be stored in container for a long time. Cold curing adhesive are prepared just before the uses there pot life is30 to 40 min.
The method of application on an adhesive is depending upon its viscosity. Liquid adhesive, tat can be applied with brushes and sprays are uses most commonly. Some grades of adhesive are convenient to apply with spatulas, roller or injectors.
The adhesive can be spread in a thin layer (0.1 to 0.2mm) with a bristle brush or a spatula. To prevent frothing the adhesive must be applied moving the brush in one direction.
In hand pneumatic injectors, compressed air is supplied through an inlet connection. The air extrudes the piston by means of piston through nozzle having a dia. of 1mm.
After the application of adhesive the parts are assembled in special fixture and clamped by means of lever mechanism, spring or pneumatic clamping devices. Clamping force must ensure a unit pressure of 0.05to 1MN/m2.
Lastly heat is heat is effected in cabinets equipped with electric or gas heater. The heating temp. and the curing temp depend upon the composition of adhesive for intake a heating temp. of 150 to 160 c and a curing time is1.5 h is needed for a cold curing adhesive  base on epoxy resin. For a hot curing adhesive based on epoxy resin, a curing time of 3 to 4h at 150 to 160 or 1.5 to 2h at180 to 190c is recommended.
 Adhesive should be chandelled very care fully as their constituents are toxic. The work therefore should be done with gloves on, under proper exhaust ventilation.

1.9.4 ADHISIVES: -
There is large variety of adhesive available for bonding with metal and metal with non-metallic materials. They can be classified into the following main group:

(1)   Adhesive Based On Epoxy Resins: -

The available epoxy resin based adhesives are both cold and hot curing. These are used to cold and hot joining of metal ceramics plastic wood and other material.
In cold curing adhesive a curing element such polythene polyamide
98 to10 parts by mass) or hexamethyldiamine (20 parts by mass) is added to 100parts by mass of resin. Maleic anhydride (40 parts by mass) is added as a curing agent to the resin in making hot curing adhesive. There various epoxy resin are used as given below with the curing given within the brackets: -
Epoxy (room temp. cure, 16to32c)
Epoxy (elevated temp. cure, 93 to 177c)
Epoxy nylon (121to 177c)
Epoxy phenoilic (121 to177c)
(2)   Phenol-Resin Based Resins: -

Various compounds modify these. Curing take place 150cwith the joined component held against each other. Phenol polyvinyl acetate is available readymade without subsequent introduction of curing agent. These adhesive can sustain temp. Up to 100 c. phenolic rubber and phenolic resin based adhesive s modified by organic solvent polymer or silicon compounds feature high temp. resistance Phenol formaldehyde issued to bond foam plastic textile laminate. The common adhesive in this group are: 
Neoprene-phenolic (135-177c)
Niotrile_phenolc (135-177c)
Butryl-phenolc (135-177c)

(3)   Polyurethane Adhesive: -

These adhesive have resistance to temp. up to 100 to 120 c and same strength as polyvinyl acetate adhesive.

(4)   Special Grade Adhesive: -  

These are used to high temp. Resistance and poses high shearing strength. Bonding Plastic Parts: -

The above-discussed adhesive and special purpose adhesive is used to bond plastic parts. For many thermoplastic these solvent serve as a adhesive, or example dichloro ethane for organic glass, benzol for polystyrene, acetone for viniplast etc. the scope of automation for adhesive-bonding process is the application of adhesive to the mating surfaces, assembly and accurate location of the parts bonded, and subsequent curing. Adhesive can be applied with roller and feed with injector into the clearance b/w the mating parts; dipping the mating parts into it is also practicable.


In almost every type of production tooling the most desirable feature to have is a very hard surface on allow strength but tough body. Toughness is needed to survive mechanical shocks that are impact loading in interrupted cuts. Shocks occur in even continuous chip formation process, when the counters the localized hard spot. The example of such tooling include metal cutting tools rock drills, cutting blades, forging die, screw for extrusion of plastic and food products and saw mills and so on. Other application include parts of earth moving machinery, valves and valves seat for diesel engines and many such parts involving high heat application and in general application requiring wear resistance. The various techniques employed for this purpose are discussed below: -

1.10.1 Hard Facing: -

It is the technique of depositing a layer of hard metal on component to increase the hardness, strength of base metal. The techniques is widely used in bearings, cam shaft, valves and valves seats, hot extrusion dies, closed dies especially for abrasive powder, earth handling, and mining equipment of many type such as rock drills stone crushers. Hammer mills shear blades and much type of cutting and trimming dies.
The composing of surfacing metal differs from that of the base metal. Hard facing materials such include satellite and other cutting and wear resistance alloys. Tip or rod from 5 to 10 mm thick, cat from satellite alloys, or used for hard facing of tool y welding technique. The cutting tool material with very hard phases has such as high alloying element concentration that they cannot be manufacture into welding rods. The ingredients are incorporated in the flux coating or packed inside tubular rods, and the alloys are formed in welding process itself.
Hard facing is by means of gas, arc or shielded arc welding techniques. Gas and shield arc welding are more uniform composition of deposited layer. Surfacing by ordinary a arc welding is cheaper and faster, but there is greater danger of dilution of metal with the base metal. Deposition of tungsten carbide by an electric arc is called spark hardening. When thick layer are deposit one speaks of weld overlays. However the thickness of deposit should not exceed than 2mm because the susceptibly to cracking increase with thicker layers.
Hard facing techniques and conditions should ensure a strong bond of the deposit with the base metal, restrict their mixing and avoid the formation of cracks and other defects in the deposit layer. Parts to be hard faced are first pre heated to 350 to500c; the hard faced parts are to be cooled slowly.
Hard facing should increase the service life of certain part by 3 to 4 times and worn parts to be repeatedly restored.

1.10 .2 Nitriding Case Hardening: -

It is surface hardening processing which the surface of steel is saturated with nitrogen. In consist of heating the part to a temp. Of 480c to 650c inside a chamber through which a stream of NH3 is passed ammonia gets dissociated:
2NH3 = 2N + 3H2.
The nitride parts very high surface hardness (730 to 1100 BHN). Nitriding increase the wear resistance in air water and water vapor.
Nitriding is usually to medium carbon and alloy steels containing Al, Cr, Mo, and other elements capable of forming nitrides. Prior to nitriding parts should be hardened tempered and undergo to the complete sequence of machining process including grinding. Only finish grinding and lapping is done after nitriding. The nitride case is usually0.2 to 0.4 mm thick.
Nitriding done at low temp. as compared to hardening and carburizing, so it requires more time. But since no quenching is necessary as the high hardness is obtain directly after the operation. The feature enables the hardening effects to be avoided. 

a)  Hard Chrome Plating:  Hard chrome plating is done by electrolytic electroplating technique. It is most common process for wear resistance.

b)     Flame Plating: - Flame plating is a process develops to prolong the life of certain type of tool and there wear applications. By this process, a carefully controlled coating of tungsten carbide, chromium carbide (Cr3C2) or aluminum oxide is applied to a wide range of base metals the more common material, which have been successfully, flame-plated include: aluminium, brass, bronze, cast iron, ceramics, copper, glass/ H.S.S., magnesium, molybdenum, nickel steel, and titanium and their alloys.
The uses a specially designed gun into which is admitted metered amount of oxygen and acetylene. A change of fine particles of the selected plating mixtures is injected into the mixture of oxygen and acetylene. Immediately a valve opens to admit he a stream of nitrogen to protect the valve during the subsequent detonation. The mixture is now ignited and the explosion is take place, which plasticizes the particles and hurls in them from gun with a velocity of 750 m/s. The particle gets embedded into the surface and a microscopic welding take place, which produces a highly tenacious bond.
Each particle in the coating is elongated and flattened into thin disc. The coating has a dense fine and grain laminar structure with negligible porosity and absence of void and oxide layer.
The layer of the plated materials about 0.006mm, this layer can build up by repeating the explosion, to thickness ranging from0.05 to0.75mm, according to the requirement of subsequent operations. The resultant layer well dense, hard and well bonded.
Because of the hard dense structure of coatings, flame plating has provided industry with a valuable tool for the solving of many abrasion, erosion and wear problem. For example bushes for many applications, core pin for powder metallurgy, dies, gauges, journals, mandrels, and seals for high duty pumps, have all being given much longer lives.           
The process has influenced considerably certain type of cutting process, especially in the glass leather, soap, and textile industries has proved to be great advantage for component involving high heat application such as “hot-end” of gas turbine.
The coating shows an excellent resistance to galling and corrosion. Flame-plated coating can be ground and lapped if necessary. Resultant surface be with in the reason of 0.025micro meter. Another advantage is that the components can be enabling to mast the coatings to be placed preciously where required.
The mixture of tungsten carbide coating can be consisting of cobalt ranging from 7% to17% and rest of tungsten carbide.
Aluminum oxide plating mixture is almost of Al2O3 (above 99%). Chromium carbide plating consist of about 75%yo 85% of Cr3C2 and balance of (Ni-Cr).

1.10.3 Chemical Vapor Decomposition: -

Chemical vapor decomposition uses volatile metal compounds, which are carried as a vapour in a glass stream and deposit as metal upon any surface that is hot enough to produce the desired reaction.
Vapor phase decomposition can be done by two methods:
i) In decomposition method a decomposition halide is vaporized metered and transported by means of inert carrier gas to the heated component, where it decomposes at the surface of yield pure metal.
ii) In the second method, a reduction process, hydrogen is used as the carrier gas through a purifier and dry hydrogen chemically reduces the halide to pure metal on the part surface as shown in fig. HFC, HFN. Multiple coating of Al2O3 can be given on top of Al2O3.coating thickness is in micrometer
For depositing a layer of TiC on carbide tool inserts a mixture of hydrogen methane and titanium trichloride gas is form in the mixing chamber. The mixture of these gases can flow through next chamber enrich carbide inserts are heated up to about 1000c by induction heating or by resistance heating. The following reaction takes near the surface of the parts:
TiCl4 +CH4 = TiC +4HCl.
TiC so produce get adhere to the surface of the substance that is WC. The main advantage of CVD process is its ability to produce:
a) High density coatings because the coatings are built by atom by atom.
b) High purity materials.
c) High strength materials.
d) And complex shapes.

An emerging coating technology used particularly for multiphase coatings, is medium temp. CVD (MTCVD). It is being developed to machine ductile iron and stainless steels and to provide higher resistance to crack propagation than conventional CVD.

Fig. 1.4 Reduction Method of CVD

1.10.4 Physical Vapor Decomposition: -

 In the basic form of PVD method applying sufficient heat with help of one of many techniques evaporates metal or an oxide. The atom or molecule so produced move in all direction. When they come into atomic or molecular attraction of the component that is the substrate they condense onto it to form a uniform coating.
In a variation of method, a cathode target is bombarded by accelerated ion. This concept dislodges or driving of single atom or small cluster into surrounding gas for deposition on a near by substrate surface. To increase coating adhesion and improve film structure, the substrate surface is heated to temp. From about 200c to500c.
PVD process particularly suited to tin coating of H.S.S. tools, because it being a relatively low temp. Processes, the tempering temp. Point of H.S.S. is not reached. So after the PVD process the heat treatment is not needed.

1.10.5 Diffusion Coatings: -

The surface hardness of low carbon steel (with carbon lees than 2%) can be increased by making hardneble by diffusing carbon or nitrogen into the surface.  On heating or quenching the carbon-nitrogen enriched surface is very hard but core remains tough. The surface can also be hardened by ‘ion nitriding’ method where the steel surface is bombarded by low energy nitrogen ions produced in plasma.

1.10.6 Ion Plating: -

In this method high-energy ion are penetrated into the surface. For cutting tools, nitrogen ions are almost commonly user. There is virtually no change in dimension in the last two processes.


Graphite is high refractory substance. Graphite moulds are used for casting metals, such as titanium, that tends to react with many common mould materials. Graphite is used for Moulding in much the same manner as plaster. For this graphite is available in an investment type of mixture, which is obtained by combining powdered graphite with cement, starch & water. This slurry is compacted around a precision mc. metal pattern. The pattern is removed & mould is fired at 1000 C, producing a solid graphite mould, which is then poured. After solidification of the metal the moulds is broken for the removal of the casting. Graphite moulds have an advantage over plaster moulds as they may be reused. Graphite moulds can also with stand with heat of grey, ductile or malleable metals. However the size of moulds of graphite is limited is the order of 50 x 45 x 25cm. casting upto a mass of about 23 kg can be produced. 

Sand can be lodged in place if air is removed from the sand mass. This principle is employed in vacuum moulding process in which no binder is used.
1. A thin plastic sheet is draped over pattern positioned over the mould board. Vacuum is drawn on the pattern. This makes plastic to be tightly drawn over the pattern surface.
2. A vacuum flask is placed over the pattern & is filted with clean unbounded sand. Pouring basin & the sprue are formed and another plastic sheet is placed over the sand.
3.  Vacuum is drawn on the sand. This makes sand very hard.
4.  Vacuum is now released on the pattern & it is withdrawn.
5.  Similarly the second half of the mould is made.

Fig. 1.5 Vacuum Moulding Process

The two moulds halves are assembled & molten metal is poured. The plastic sheet will burn up. When the casting is solidified, vacuum on the flask is released. The sand collapse and the casting are taken out.
The process is also known as V-process & has followed.

1.12.1 Advantages
1.      Saving on the binder cost, as no binder is used in process.
2.      No defect released to moisture & binder fumes.
3.      Any sand can be used 
4.      Easy shake out. However the process is quit slowly. 


Composite materials can be defined as the structures made up of two or more distinct starting materials. The starting materials can be organic, metals or ceramics. The components of composite materials do not occur naturally as an alloy, but are separately manufactured before these are combined together mechanically. Due to this, they maintain their identities, even after a composite material is fully formed. However the starting materials combine to rectify a weakness in one material by strength in another material. Hence composite material exhibits properties distinctly different from those of individual materials used, to make composite. Thus composite material or structure possesses a unique combination of properties such as stiffness, strength, hardness, weight, conductivity, corrosion resistance & high temp. Performance etc. that is not possible by individual materials. Thus the search for materials with special properties to suit some specific stringent conditions of use has given rise to development of materials called “COMPOSITE MATERIALS”.


Composite materials may roughly be classified as:

1)      Agglomerated materials/ Particulate composites.
2)      Reinforced materials.
3)      Laminates.
4)      Surface coated materials.

The particulate composite and reinforced composites are constituted by just two phases, the matrix phase. The aim is to improve the strength properties of matrix material. The matrix material should be ductile with its modulus of elasticity much lower then that of dispersed phase. Also the bonding forces between the two phases must be very strong.
In fact the particulate composite also fall in the category of reinforced composites. Depending upon the nature of reinforced materials (shape and size), the reinforced composites can be classified as
1.      Particle reinforced composites or particulate reinforced composites.
2.      Fiber reinforced composite.

In particulate reinforced composites, dispersed phase is in the form of exi-axed particles, whereas in fibre-reinforced composite, it is in the form of fibers. AGGLOMERATED MATERIALS:

Agglomerated materials consist of discrete particles of one material, surrounded by matrix of another material. The material is bounded together in an integrated mass to classic eg. Of such composite material are: concrete formed by mixing gravel, sand, cement & water & agglomeration of asphalt & stone particles, that is used for paving the high surfaces. Other eg. Of particulate composite material includes:

1)       Grinding and cutting wheels, in which abrasive particles (Al2O3, Sic, CBN or carbon) are held together by a vitreous or a resin bond.
2)       Cemented carbide, in which particles of ceramic materials such as WC, TaC, TiC & of cobalt & nickel, are bounded together via Powder metallurgy process to produce cutting tool materials. Many powdered metal parts & solid sintering produces various magnetic & dielectric ceramic materials, which requires diffusion.
3)       Electrical contact point from powder of tungsten & silver or copper is process via powder metallurgy method.
4)       Electrical Brushes for motored & heavy duty & frictional materials for brake & clutches by combining metallic & non-metal. Materials.
5)       Cu infilterated iron & silver, tungsten.
6)       Heavy metal (w+6%ni+4%cu)
7)       Electrical resistance welding electrodes from mixture of cu & tung.
8)       Shell moulding sand, using a resin binder, which is polymerized by hot pattern.
9)       Metal polymer structers (metal bearing in filtered with nylon or PTFE).
10)   Particleboard, in which wood chips are held together by suitable glue.
11)   Elastomers & plastics are also reinforced with suitable particle material. The eg. Is addition of 15-30 of carbon black in the vulcanized rubber for automobiles types?
12)   Dispersion strengthened materials: in these materials hard, brittle and fine particles are dispersed in softer or more ductile matrix.
Because of their unique geometry, the properties of particulate composite can be isotropic. This property is very important in many engineering applications REINFORCED MATERIAL:

Reinforced materials from the biggest and most important group of composite materials. The purpose of reinforcing is always to improve the strength properties. Reinforcement may involve the use of a dispersed phase (discussed in the last article) or strong fiber, thread or rod.

Fiber-reinforced materials: in a larger number of applications, the material should have high strength, along with toughness and resistance to fatigue failure. Fiber reinforced materials, offer the solution. Stronger or higher modulus filler, in the form of thin fibers of one material, is strongly bonded to the matrix of another. The matrix material provides ductility and toughness and supports and blinds the fibres together and transmits the load. The toughness of the composite material increases, because extra energy will be needed to break or pull out a fibre. Also, when any crack appears on the surface of a fibre, only that fibre will fail and the crack will not propagate catastrophically as in bulk material. Failure is often gradual, and repairs may be possible.
 Due to the above mentioned desirable properties of the matrix materials, the commonly used matrix materials are; Metals and polymers, such as, Al Cu, Ni etc. and commercial polymers strong fibers in the relatively weak matrix. Like this, it is possible to produce parts where strength control is developing in different directions. if the  part is loaded parallel to the fibers will be much greater than in the matrix . Even if the fibre breaks, the softness of matrix hinders the propagations of crack .The fibre direction are tailored to the direction of loading.

Reinforced Fibers: A good reinforcing fibre should have: high elastic modulus, high strength, low density, reasonable ductility and should be easily wetted by the matrix. Metallic fibres such as patented steel; stainless steel, tungsten and molybdenum wires are used in a metal matrix such as aluminum and titanium. Carbon fibers and whiskers are also used in a metal ultra –high strength composite. Fibres need not be limited to metals. Glass, ceramic and polymer fibers are used to produce variety of composite having wide range of properties .The high modulus of ceramic fibers make them attractive for the reinforced of the metal. The ductile matrix materials can be aluminum magnesium, nickel or titanium and the reinforcing fiber may be of boron , graphite , aluminum or SiC.

Forms of reinforcing fibres: The fibers used for reinforcing materials are available in different forms:

(a)    Filaments: these are very long and continuous single fibres.
(b)   Yarns: this is twisted bundles of filaments.
(c)    Roving: These are untwisted bundles of gathered filaments.
(d)   Tows: These are bundles of thousands of filaments.
(e)    Woven fabrics: These are made from filaments, yarn or roving which have been woven at 90 degree to each other.
(f)    Mats: Fibre form is said to be mat form when the continuous fibre is deposited in a swirl pattern or chopped fibre is deposited in a random pattern.
(g)   Combination mat: Here, one ply of woven roving is bonded to a ply of chopped strand mat.
(h)   Surface mats: These are very thin, monofilament fibre mats for better surface appearance.
(i)     Chopped fibre or roving: These are 3 to 50 mm in length.
(j)     Milled fibres: These are of brittle materials, usually 0.5 to 3 mm in length.
(k)   Whiskers: whiskers are single crystal, in the form of fine filaments, a few microns in diameter and short in length. These single crystal whiskers are the strongest known fibers. Their high strength is due to the high degree of perfection and the absence of dislocation in the structure. Their strength is many times greater than that of the normal metals. For ex The strength of an iron whisker is found to be 13450MN\m2, compared to about 294MPa for a piece of pure iron,. Besides metal whiskers, long non metallic, whiskers and of graphite are being produced. They are introduced in to resin or metallic matrix for the purpose of high strength and high stiffness at high temperatures.
The properties of reinforced materials will depend on:
  • The properties of matrix materials.
  • The properties of the fibre materials.
  • The proportions of the reinforcement in the composite materials. It is never less than 20% and may go up to 80% in oriented structures.
  • The orientation of the fibre, relative to the load application and relative to one another.
  • The degree of bonding between the fibers and the matrix material.
  • The length to diameter ratio of the fibers.There has to be some minimum fibre length, known as, critical length, lc, to get the desired strength and stiffness of the composite materials. It is given as:

L c =  σ f .d / ح

Where,      σ=Tensile strength of fibre materials
      d =diameter of fibre
                  ح =shear yield strength of the fibre matrix bond

Fig. 1.6 Reinforcing Fibers

For example, for carbon and glass fibers, the critical length is of the order of 1mm, which may be 20 to150 times the diameter of the fibre.

The fibre reinforcement can be done in three ways:
1. Continuous and aligned, Fig a
2. Discontinuous and aligned, Fig b
3. Continuous and randomly oriented, Fig c

If the fibre length is considerably greater than Lc e.g., 15 times or more, it is called a “continuous fibre”, otherwise it is called “short” or “discontinuous fibre as noted above, the properties of a composite having aligned fibre reinforcements, are highly anisotropic, that is, they depend upon the direction in which these are measured. Their maximum strength is along the direction of alignment. They are very weak in the transverse direction. The arrangement is best suited for application involving multi- direction applied stresses, for e.g., bi-axel stresses in pressure vessel or tube. The same results can be achieved by using bi- axially oriented or cross – ply fibers. It is apparent that the strength of the discontinuous and aligned arrangement will be less than of the continuous and aligned arrangement.

Applications: As discussed in the beginning, composite structures combine the desirable properties of two or more materials. This has greatly expanded the scope of application of all engineering materials. This has greatly expanded the scope of application of all engineering materials. We can produce components with exceptional strength –to –weight and stiffness –to-weight ratio (many composite are stronger than steel, lighter than steel and stiffer than titanium). Also, they have low conductivity, good heat resistance, good fatigue life, adequate wear resistance and are free from corrosion.
Reinforced concrete is a classic example of reinforced materials. Steel rods used in the concrete to reinforce the material take all tensile loads since concrete weak in tension but strong in compression.

1.      Glass- fibre reinforced Plastics: Here, we have glass fibres in a matrix of unsaturated polyester. To get better qualities to use at high temperature, high temperature polyamide resin is used with pure SiO2 fibres. A special type of glass fibre can be used with cement bond to form flexible type of concrete. Glass fibre reinforced plastics are used to make: boat hulls, car bodies, truck, cabins and aircraft fittings. The other matrix materials can be: vinyl ester and phenolic.
2.      C-C composites: These composites have graphite fibres in a carbon matrix. This material is being used to make: Nose cone and leading edge of missiles and space shuttles, racing car disks brakes, aerospace turbine and jet engine components, rocket nozzles and surgical implants.
3.      Graphite fibre- reinforced epoxy :( Organic or Resin matrix composites): This material is being used to make many parts of a fighter plane: Wing span, outrigger flaring. Overwing flaring, engine access doors, nose cone, forward fuselage. Lid fence and strakes-flap. Flap slot door, aileron seals, Horizontal stabilizer (Full span) and rubber. The other fibre-matrix combination can be: Aramid fibre-Phenolic resin matrix, Boron fibre-Bismaleimide resin matrix.
4.      Automative uses: Body panels, drive shafts, spring and bumpers, Cab shell and bodies, oil pans, fan shrouds, instrument panels and engine covers.
5.      Sports equipment: Golf club shafts, base ball parts, fishing rods, tennis rackets, bicycle frames, skis and pole vaults.
6.      Rubber used for making automobiles tyres is now reinforced with fibres of nylon, rayon steel or Kevlar, to provide added strength and durability. Kevlar is an organic aramid fibre with very high tensile strength and modulas of elasticity. Its density is about half of that of aluminum and it has negative thermal expansion. It is flame retardant to radio signals. This makes it very attractive for military and aerospace applications. It is also being used for making bullet proof jackets. The trade name “Kevlar” is given by Du Pont.
7.      Metal matrix composite (MMC): As already noted, these composites are obtained by impregnating high-strength fibres (of stainless steel, boron, tungusten, molybdenum, graphite, AL2O3, SiC and Si3N4 etc.) with molten metal ( aluminuim , titanium, Ni and cobalt etc). These composites offer higher strength and stiffness especially at elevated temperatures and lower co-efficient of thermal expansion as compared to metals. And as compared to Organic-matrix composites, these composites offer grater heat resistance and improved thermal and electric conductivity. Hence metal matrix composites are used where operation temperature is high or extreme strength is desired. These will find applications in a variety segments like automobiles and machinery.
Aluminum oxide reinforced aluminum is used for making automotive connecting rods. Aluminum reinforced with SiC whiskers is used to make air craft wing panels. Fibre reinforced super alloys are used for making turbine blades. Graphite fibres in aluminum matrix are used for Satellite, missile, helicopter structures.Graphite fibres in magnesium matrix is used for space and satellite structures. Graphite fibres in lead matrix are used for Strong –battery plates. A graphite fibre in copper matrix is used for bearings and electrical contacts. Other e.g. of MMC is:
(a)    Boron fibre in aluminum: Compressor blades and structural supports.
(b)   ““ “ magnesium : Antenna structures.
(c)    “””” Titanium: Jet-engine fan blades.
(d)   Alumina ““    Lead: Strong-battery plates.
(e)    ““     “     Magnesium: Helicopter transmission structures.
(f)    SiC “‘    Super alloy (Cobalt based): High temperature engine components.
(g)   Tungsten and Molybundum fibres in Super alloy matrix: High temperature engine components.

8.      Ceramic-matrix composites: (CMC): AS already noted, ceramics are strong, stiff, can resist high temperatures, but generally lack toughness. Ceramic matrix materials are: AL2O3, SiC and Si3N4, and mullite (a compound of Al, Si, and O2). They can retain their strength upto 1700 degree C, and also resist corrosive environments.
Typical product applications of ceramic matrix composite are: in jet and automotive engines, deep-sea mining equipment, pressure vessels, structural components’ cutting tools, and dies for extrusion and drawing operations.
Composite in development stage:
1.      Advance bismaleinmide resin matrix series for high temperature service.
2.      Polyether ether ketone thermoplastic matrix series for higher temperature service.
3.      Hybrid reinforcements and Knitted/stacked ply fabrics and three-dimensional woven fabric reinforcements.
4.      Selective stitching of collated ply kits.


Laminates or laminar composites are those structures which have alternate layers of materials bonded together in some manner some common examples of laminar composites are given below:
1.      Plywood: it is most common material under this category. Here, thin layer of wood veneer are bonded with adhesives. The successive layers have different orientations of the grain or fibre; Structural parts capable of carrying a load are made of multi-plywood board from 25 to 30 mm thick.
2.      Bimetallic strips used in thermostats & other heat sensing application.
3.      Safety glass
4.  Sandwich material: Here, low density core is placed between thin, high strength
High-density surfaces, for example, corrugated cardboard. Cores of polymer foam or honeycomb structures can be used. Wood substitutes based on red mud polymer have been developed to be used for door shutters, windows, partitions and false ceilings.
5.      Roll cladding (bonding) and explosive cladding (welding) of one metal upon another: The main aim of clad material is to improve corrosion resistance while retaining low cost, high strength and /or lightweight. Mild steel –stainless steel combination, copper stainless steel combination are examples of metal-to-metal laminates. Another example is “Alclad”, which is formed by cladding duralumin with thin sheets of pure aluminium. The material is high strength composite in which aluminium cladding provides galvanic protection for the more corrosive duralumin. The above claddings are done by “hot roll bonding” method.
6.      Laminated Plastic Sheet: This structure is usually made from sheets of paper or cloth and suitable resin. The resin used includes: phenolics, polyster,silicones and epoxide. The paper and cloth provides bulk of strength, while the resin acts as a semi rigid binder. Laminated plastic sheet can be machined, drilled, punched and pressed to shaped. It is used in the production of gears, bearings, electrical components, and small cabinets. Laminate fabric base gears have the advantages over metal gears of being silent in operation and stable against the attack of various. Aggressive media. In many cases, laminated fabric base gears have completely replaced nonferrous gears. They are employed to transmit rotation from electric motor in high-speed machine tools; they are mounted on the camshafts of internal-combustion engines etc. In chemical industry, laminate fabric base gears are used in various apparatus & instruments where they resist corrosive attack much more efficiently then gears of bronze brass or leather. In addition to gears, certain other transporting devices: roller, rings etc. are also made of laminated fabric base. Laminated sheets /plates are available in sizes of: 900*900 mm, 900 *1800 mm, and 1200*2400 mm. The minimum thickness of sheet is 0.8 mm & it varies as follows: -
Thickness range (mm)    0.8-1.6      1.6-4.8      6.4-9.6       12.8- 19.2      25.6- 38.4
                    Step(mm)           0.4            0.8            1.6                  3.2                  6.4
  1. Tufnol: this is a laminated material consisting of layers of woven textiles impregnated with a thermosetting resin. The polymer imparts rigidity, while the woven textile provides great tensile strength. Paper or asbestos may also be used as alternative reinforcements. The material (with woven textile) can be used for making seat covers &carpets.
  2. Laminated carbides: In laminated carbides, laminates consisting of a hard thin surface layer TiCand the form of throw away tips, are bonded by epoxy resin to the rake face of a tip body of WC. This increases the crater wear of WC cutting tool.
  3. Laminated wood : this sheets of wood (veneer ) , impregnated with special resins & compressed hot , form what is called ‘laminated wood ‘, which find extensive application in textile machinery & electric engineering , as well as substitute for nonferrous metal in bearing of hydraulic machinery &mechanisms operating in abrasive media . Parts of wood are machined in ordinary machine tools &wood working machinery.

Surface coated materials: the surface coating is applied to the materials for various purposes: - protection of the material against corrosion; for decorative, wear resistant &processing purpose. They may also be used to :(i) improve visibility through luminescence & better reflectivity (ii) provide electrical insulation , & (iii) improve the appearance. Surface coating are usually classified as: metallic coatings, inorganic chemical coating & organic chemical coating

1.   Metallic coating: metallic coating of copper, chromium nickel, zinc, lead & tin etc.  are applied by hot dipping , electro- plating or spraying techniques to protect the base metal from corrosion & for other purpose .
2. Inorganic chemical coating: This surface coating may be divided into: Phosphate coating, oxide coating & vitreous coating. Oxide & phosphate coating are done to make iron or steel surface free from rust & this is done by chemical action. These coating also provide protection against corrosion. Vitreous coating are commonly applied to steel in the form of a powder or frit & are then used to the steel surface by heat. These coating are relatively brittle, but offer absolute protection against corrosion. Enamel is an example of ceramic coating on metal & glaze on tiles is an example of glassy ceramic on crystalline ceramic base. The glazing as a protective coating on porcelain & stoneware ceramic is performed for the purpose of protection from moisture absorption in ceramic materials. Coating of TiC , TiN , Al2o3 or HFN on WC base are examples of ceramics on ceramic & coatings of TiC & TiN on HSS base are examples of ceramics on steel. These coatings increase the life of cutting tools.
3.  Organic Coatings:  It includes paint, varnishes, enamels & lacquers. They serve to protect the base metal & to improve its appearance.

Polymer coating on paper are used for making milk cartons. Polymer coated textiles are used for making seat covers & carpets. Polymer Coatings on metals act as wire insulation. Polymer coated metals are used for making beverage cans.


Fabrication of particulate composites: As discussed in above art. A majority of the particulate composites are made via the powder metallurgy route. So, for details readers should refer to chapter 10. However, a few particulate composites are made by dispersing the particles in the matrix materials through introduction into slurry or into a liquid melt (agglomeration of asphalt and stone particles).  

Fabrication of Fibre reinforced Composites:  Many processes have been developed to fabricate fibre-reinforced composite structures. Their aim is to combine the fibre and the matrix into a unified form. The various fabrication techniques depend on: the size and the form of the fibres and their orientation in the matrix material; the shape, size and form of the product. The common fabrication processes are: Open-Mould process, Filament winding, Pultrusion and Matched-die-Moulding, and Laminating. Before these processes are discussed, the following terms should be understood:

·         Prepergs: Prepergs means “Preimpregnated with resin”. It is ready to mould material in the sheet form. Impregnated rovings and mats make these with resin matrix under the condition in which the resin undergoes only a partial cure. These are stored for subsequent use. These are supplied to the fabricator, who lays up the finished shape in stacks, which is subjected to heat and pressure. This completes the curing of the resin into a continues solid matrix. “Lay-up” is positioning of the reinforcement material, sometimes resin-impregnated, in the mould.
·         BMCs:  are “Bulk Moulding Compounds”. These are thermosetting resins mixed with chopped reinforcements or filters and made into a viscous compound for compressing moulding.
·         SMCs: are “Sheet Moulding Compounds”. These comprise chopped fibres and resin in the sheet form approx. 2.5 mm thick. These are3 processed further to fabricate large sheet like parts. They can replace sheet metal, where lightweight, corrosion resistance and integral colour are attractive features.
·         Thick Moulding Compounds: Thick Moulding Compounds (TMC) combines the lower cost of BMC and higher strength of SMC. These are usually injection moulded using chopped fibres of various lengths. Used for electrical components due to their high electrical strength.

1) Open – Mould Process ~ In this process, only one mould (Die) is employed to fabricate the reinforced part. The mould may be made of: wood, plaster or reinforced plastic material. The various techniques in this category are:-
a)      Hand lay-up technique: In this method, the successive layers of reinforcement mat or web (which may or may not be impregnated with resin) are positioned on a mould by hand. Resin in used to impregnate or coat the reinforcement. Curing the resin to permanently fix the shape then follows it. Curing may be at room temperature or heating may speed it up. The technique in which resin-saturated reinforcements are placed in the mould is called   “Wet lay-up”.
b)     Bag Moulding: This is a technique of moulding reinforced plastics composites by using a flexing cover (bag) over a rigid mould. The composite material is positioned in the mould and covered with the plastic film (bag). Pressure is then applied by a : Vacuum, auto-clave, press  or by inflating the bag . An auto-clave is a closed pressure vessel for inducing a resin cure or other operation under heat and pressure.
i)        Vacuum-bag moulding: In this technique for moulding reinforced plastics, a sheet of flexible, transparent material is placed over the lay-up on the mould. After sealing the edges the entrapped air between the sheet and the lay-up is mechanically worked out and removed by the vacuum. Finally, the part is cured.

Fig. 1.7 Vacuum Bag Moulding
ii) Pressure-bag Moulding: It is a process for moulding reinforced plastics in which a tailored, flexible bag is placed over the contact lay-up on the mould, sealed and clamped in placed. Compressed air forces the bag against the part to apply pressure while the part cures.
iii) Spray-up: In this technique, a spray gun supplies resin in two converging streams into which chopped roving fiber is forced with the help of a chopper. The composite material stream is then deposited against the walls of the mould cavity. It is a low-cost method of fabricating medium strength composite structures.
All the above open-mould techniques are extensively used for fabricating parts such as: boats, tanks, swimming pools, ducts and truck bodies.

2) Matched-die moulding: Matched metal dies are used for moulding composite structure when: production quantities are large, tolerances are close and surface quality has to be the best. The dies are heated to complete the curing of the product during the moulding process.

i) Compression Moulding is essentially employed for moulding BMCs.

ii) Resin- Transfer Moulding or Resin Injection Moulding: In this technique (RTM or RIM), two piece matched cavity dies are used with one or multiple injection points and breather holes. The reinforcing material, which is either chopped or continuous strand material is cut to shape and draped in the die-cavity. The die-halves are clamped together and a polyester resin is pumped through an injection port in the die. The pressure used in the die is low, which allows use of low cost tooling. The method is used for moulding small non-load bearing parts.
In a variant of the above technique, instead of the injection of only resin into the die-cavity, the reinforcement (flake glass) is mixed with the resin in a mixing head and the mixture is injected into the closed heated two-piece die. Flake glass is preferred to avoid directionality of reinforcement. This method is known as “Reaction Injection Moulding” and is being increasingly used for BMCs.

iii) SMCs cut to size, are fabricated into parts by methods similar to metal pressing. However, curing of the part takes place outside the press.  

Fig. 1.8 Compression Moulding
3) Pultrusion: This is the process of extrusion of resin-impregnated roving ( a bundle of fibres ) to manufacture rods, tubes and structural shapes (Channels, I-beams and Z- Sections etc.) o0f a constant cross-section. After passing through the resin-dip tank, the roving is dawn through a heated die (where curing takes place) and cured to form the desired cross-section, as it continuously runs through the machine. After the Puller rolls, a saw cutter cuts the extruded section to the required lengths.
In “ Pulmoulding”, the process begins with pultruding; then the part is placed in a compression mould.
Product applications are: - Golf club shafts, because of their high damping capacity, and structural members for vehicle and aerospace applications.
Fig. 1.9 Pultrusion

4) Filament Winding: In this process, resin impregnated strands are applied over a rotating mandrel, to produce high strength, reinforced cylindrical shapes. Fibers or tapes are drawn through a resin bath and wound onto a rotating mandrel. The process is relatively slow, but the fiber direction can be controlled and the diameter can be varied along the length of the piece. In a variation, the Fiber bundle (made up of several thousand carbon fibers) is first coated with the matrix material, to make a prepreg tape (endless strip with width equal to several cms, by a meter). With both the fiber and tape winding processes, the finished part is cured in an autoclave and later removed from the mandrel. In axial winding, the filaments are parallel to the axis and in circumferential winding; these are essentially perpendicular to the axis of rotation.
Cylindrical, spherical and other shapes are made by filament winding, for example, pressure bottles, missile canisters, industrial storage tanks and automobile drive shafts C- fibers with epoxy- basin resin composite is used for fabricating strength- critical aerospace structures.

Fig. 1.10 Filament Winding Process

5) Laminating:  In this process, composite parts are produced by combining layers of resin-impregnated material in a press under heat and pressure. The parts include, standard for comparatively flat pieces. Two principal steps in the manufacture of laminated fiber-reinforced composite materials are:-
(a) Lay-up, which consists of arranging fibers in layers.
(b) Curing
We start with a preperg material (partially cured composite with the fibers aligned parallel to each other). A pattern of product’s shape is cut out the preperg material is then stacked in layers into the desired laminate geometry. Curing the stacked pile under heat and pressure in an autoclave makes a final product, or by tool press moulding, winding the impregnated fibre on a mandrel of suitable diameter produces tubes. The assembly is then cured in a moulding press and then the mandrel is removed.

Basically, three approaches are followed for fabricating MMC

1. Liquid phase approach: In this technique, the matrix material is the molten phase and the reinforcement is in the solid state. Either one of the conventional casting process can be used to fabricate MMC or “Pressure infiltration casting method “can be used. In this method, a perform is made (usually a sheet or wire) of reinforcing fibres and the liquid metal matrix is forced into it with the help of a pressurized gas.

2. Solid phase technique: Here the Powder Metallurgy route is used to fabricate MMC. The best example is of manufacturing WC tool material where cobalt is used as the matrix material.

3. Two phase Processing: Here the metal matrix contains both the solid and liquid phases. The reinforcing fibres are mixed with the matrix. The mixture is then atomized when it leaves the nozzles and is sprayed and deposited over the surface of a mould cavity to fabricate MMC.


The most common method of fabricating CMC is of “Slurry infiltration”. A perform of reinforcing fibres is prepared which is then hot pressed. Slurry containing matrix powder, a carrier liquid and an organic binder is prepared. The perform is then impregnated with the slurry to fabricate CMC.


Conventional processes and tools are generally not suited for machining, cutting and joining of composites. Therefore, special methods are employed to the final processing operations for the composites.

1. Machining: Machining of composite materials should ensure that there is no splintering, cracking, fraying or delaminating of cured composite edges. Standard machine tools can be used with appropriate modifications. Cutting tools for composites include: drills, reamers, countersinks, cut-of wheels and router bits. Common cutting tool materials are: HSS and WC. However, poly-crystalline diamond insert tool performs satisfactory and is cost effective. Tools must be kept sharp, to provide quality cuts and avoid de-lamination. Tool and its geometry should be carefully selected. Cutting speeds and feeds will depend on the type of composite material, its thickness and the cutting method.

2. Cutting: The conventional methods for cutting uncured composites, such as preperg ply include: manual cutting with Carbide disk cutter, scissors and power shears. For cutting uncured composites, the main techniques are: reciprocating knife cutting, high pressure water jet cutting, ultrasonic knife cutting and laser cutting.

3. Joining: The common joints provided for composites structures are: Bolted joints and Adhesive bonded joints.

Prepared By- Er. CP SINGH
(Asst. Prof)
(Mech Engg Dept)

     E-Max Group of Institutions, Ambala