Introduction to Manufacturing

Process

Casting Processes• These are the only processes where

liquid metal in used.• Casting is the oldest known

manufacturing process.• It requires preparation of a cavity usually

in a refractory material to resemble closely to the object to be realized.

• Molten metal is poured into this refractory mould cavity and is allowed to solidify.

• The object after solidification is removed from the mould.

Forming Processes• These are solid state manufacturing processes involving minimum amount of

material wastage and faster production.• Metal is heated to a temperature which is slightly below the solidus temperature

and then a large force is applied such that the material flows and take the desired shape.

• The desired shape is controlled by means of certain tools called dies which may be completely or partially closed during manufacture.

• These processes are normally used for large scale production rates.

Rolling Process

Drop forgingExtrusion

Wire Drawing

Fabrication processes• These are secondary manufacturing processes where the starting raw materials are processed by any of the previous methods.•It essentially involves joining pieces either temporarily or permanently so that they would perform the necessary function.•The joining can be achieved by both heat and pressure and / or a joining material.

Gas Welding

Arc Welding

Resistance Welding

Material Removal Processes• These are also secondary manufacturing processes where the additional unwanted

material is removed in the form of chips from the blank material by a harder tool so that a final desired shape can be obtained.

• Material removal is the most expensive manufacturing process because more energy is consumed, and also a lot of waste material is generated in the process.

Turning

Milling

Shaping

Drilling

Grinding

Sawing

Abrasive Machining Categories• The Metal abrasion action is adopted during grinding,

honing and super finishing processes that employ either a solid grinding wheel or sticks in the form of bonded abrasive.

• Furthermore in lapping, polishing, and buffing, loose abrasives are used as tools in a liquid medium.

The requirements that lead to the development of nontraditional machining

• Very high hardness and strength of the material.

• The work piece is too flexible or slender to support the cutting or grinding forces.

• The shape of the part is complex, such as internal and external profiles, or small diameter holes.

• Surface finish or tolerance better than those obtainable conventional process.

• Temperature rise or residual stress in the work piece are undesirable.

Conventional Machining VS NonConventional Machining

• The cutting tool and workpiece are always in physical contact, with a relative motion against each other, which results in friction and a significant tool wear.

• In non-traditional processes, there is no physical contact between the tool and workpiece. Although in some non-traditional processes tool wear exists, it rarely is a significant problem.

• Material removal rate of the traditional processes is limited by the mechanical properties of the work material. Non-traditional processes easily deal with such difficult-to-cut materials like ceramics and ceramic based tool materials, fiber reinforced materials, carbides, titanium-based alloys.

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• In traditional processes, the relative motion between the tool and work piece is typically rotary or reciprocating. Thus, the shape of the work surfaces is limited to circular or flat shapes. In spite of widely used CNC systems, machining of three-dimensional surfaces is still a difficult task. Most non-traditional processes were develop just to solve this problem.

• Machining of small cavities, slits, blind or through holes is difficult with traditional processes, whereas it is a simple work for some non-traditional processes.

• Traditional processes are well established, use relatively simple and inexpensive machinery and readily available cutting tools. Non-traditional processes require expensive equipment and tooling as well as skilled labor, which increases significantly the production cost.

Advanced cutting tool materials (a) Coated carbides - TiC, TiCN, TiN, Al2O3

(b) Cermets -These sintered hard inserts are made by combining ‘cer’ from ceramics like TiC, TiN ( or )TiCN and ‘met’ from metal (binder) like Ni, Ni-Co, Fe etc. (c) Coronite -Coronite is made basically by combining HSS for strength and toughness and tungsten carbides for heat and wear resistance. Microfine TiCN particles are uniformly dispersed into the matrix

(d) High Performance Ceramics (HPC) -Sinterability, microstructure, strength and toughness of Al2O3 ceramics were improved to some extent by adding TiO2 and MgO (e) Cubic Boron Nitride (cBN) (f) Diamond