Manufacturing process

MANUFACTURING PROCESS

MANUFACTURING PROCESS

Raw material finished product

Classification1. Shaping process2. Machining process3. Joining process4. Finishing process5. Property changing process

Process

1. Shaping process Process in which shape and size of material is

changed without removal of material.

Common process :- CastingForging DrawingRollingExtruding

2. Machining process Process in which shape and size of material is

changed by removing material from unwanted portions of the work piece.

Common process:-Surfacing TurningShapingDrillingGrinding Milling

3. Joining process Process in which two or more parts are joined

together.

Common process :-WeldingBrazingSolderingBoltingRivetingShrink fitting

Moulding and Casting Casting : Process of producing metallic parts of desired

shape and size by pouring molten metal into a mould having a cavity and allowing the molten metal to solidify.

Moulding: Process of making mould using a pattern.

Pattern : Replica or model of the final product.

Mould materials : sand, plaster of Paris, metal etc

Pattern material : wood, metal, wax, plastic, cement etc

Moulding box

Classification of Moulding 1. Bench moulding

done on a bench Used for small castings

2. Floor moulding moulding done on foundry floor Used for medium and large moldings

3. Pit moulding Moulding done on pits dug on foundry floor. Drag part in pit & separate cope Used for extremely large castings

4. Machine moulding operations such as ramming, pattern removal are done by

machines. Faster method used for mass production. Better quality and cost of production less due to mass production.

Properties of moulding sand

1. Porosity or permeability2. Cohesiveness or strength3. Adhesiveness4. Plasticity 5. Refractoriness6. Flowability 7. Chemical stability

Sand Casting Sand moulds

Moulding box – cope and drag.

Gating system – passage for bringing molten metal to mould cavity. It consist of Pouring basin Sprue Gate

Core – solid mass of dry sand, having shape of internal cavity or hole in casting.

Permanent mould casting Moulds are made of metals (cast iron and alloy steel). Pouring molten metal into the cavity without applying

external pressure (gravitational force only). Mould halves are hinged for easy removal of casting.

Advantages : Closer dimensional tolerances. Better surface finish. Greater mechanical strength Lower percentage of rejection.

Disadvantages : Not suitable for large castings. Cost high Used for mass production only.

Die Casting External pressure (pneumatic, hydraulic,

mechanical) is employed (pressure die casting) for casting.

Fast casting process Metallic mould called Die. Used for lead, Mg, tin, Zinc alloys, Al, copper

etc.

Types of Die casting1. Hot chamber Die casting.2. Cold chamber die casting.

Hot chamber die casting

A piston is actuated inside the cylinder .Cylinder is having a goose neck at one end.A port is provided near the top of the cylinder to allow molten metal to enter into it.The downward stroke of the piston closes this port and applies pressure on the molten metal.Thus molten metal is forced into the die cavity and solidifies to form a casting.

Cold chamber die casting

Metal is melted separately and transferred to the cylinder using a hand ladle.After closing the die, the molten metal in the cylinder is forced into the die cavity by applying pressure on the piston.After solidification the die is opened and casting is ejected

Advantages of die casting: Very high rate of production Very close dimensional tolerances High surface finish Economical for mass production Intricate shape can be easily cast Thin sections can be casted easily.

Disadvantages of die casting All types of alloy cannot be cast Not suitable for large casting High cost of die and die casting equipments.

Advantages and disadvantages of die casting equipments No limit of size of parts that can be produced by

casting Wide range of materials can be easily cast. Cheapest method for mass production. Intricate shape can be cast. Not economical for few number of castings.

Forging Definition : process of changing shape of

metals when it is in plastic state, by applying compressive force, is called hot forging or simply forging.

Hand Forging Drop Forging Press Forging Machine Forging

Upsetting Drawing Down

Bending Punching

ROLLING Rolling is the process of forming metals into

desired shape by passing the metal in between a pair of roller . The two rolls rotated in opposite direction at same speed. The arrangement of rolling for rolling operation is called rolling mill. Example ;bars, plates, sheets, rails

Hot rolling ;metal heated above recrystallizition temp

Cold rolling ; metal heated below the recrystallizition temp

Basis of no: of roller and their arrangements rolling can be classified into ,

Two high mill

Three high mill

Four high mill

Cluster mill

EXTRUSION Extrusion is the process of forming

products of uniform cross sectional shapes in convenient length.

It consist of compressing the metal inside a chamber and forcing it out through a die having an opening in the shape of the cross section of the product

It can be classified into two

Direct Extrusion (Forward Extrusion) Indirect Extrusion ( Backward Extrusion)

Direct Extrusion (Forward Extrusion)

In this process the metal is placed in the die

chamber and it is forced through the die opening

by applying pressure on the ram.

Indirect Extrusion ( Backward Extrusion)

In this case, the extruded part moves out in a direction opposite to that of ram movement.

This process requires less fore than direct extrusion process.

Welding

Welding is the process of joining two metals by the application of heat . Welding is done with the help of a welding machine . Welding are classified into

Electrical resistance welding Arc welding Gas welding Thermit welding

Electrical resistance welding

w/p to be joined are held together and electric current of low voltage and high current is passed through them

Voltage: 6 to 10 Volts Current: 60 to 4000 A

Seam WeldingFlash Welding

Butt WeldingSpot Welding

Arc Welding Surface to be joined are

fused by the heat produced from an electric arc.

When electrode is kept at a short distance from the work piece, an electric arc is formed in which electrical energy is converted into heat

Electrodes are coated with Slag or Flux materials

Gas Welding It is a fusion welding in

which the required heat is obtained by the combustion of fuel gas

A gas flame ( Oxy acetylene flame) is mostly used to produce the welding temperature of the order of 3200 C⁰

Thermit Welding It is a fusion welding process

in which the required heat is obtained by an exothermic chemical reaction

A mixture of powdered aluminium and iron oxide is placed inside the crusible.

This mixture is ignited The resultant products are

highly purified iron and aluminium oxide

The temperature produced will be above 3500 C⁰

Fe2O3 + 2 Al → 2 Fe + Al2O3

BRAZING SOLDERING In case of brazing joining of

metal pieces is done with the help of filler metal.

Filler metal is melted and distributed by capillary action between the surfaces of the metallic parts being joined.

In this case only filler metal melts.

There is no melting of workpiece metal.

The filler metal (brazing metal) should have the melting point more than 450 C. ⁰

Its melting point should be lesser than the melting point of workpiece metal.

Soldering is very much similar to brazing

Its principle is same as that of brazing.

The major difference lies with the filler metal.

The filler metal used in case of soldering should have the melting temperature lower than 450 C⁰

Strength of soldered joint is much lesser than welded joint and less than a brazed joint.

Powder Metallurgy It is the process of pressing fine powdered materials into

desired shape and size and heating it in a controlled

atmosphere to bond the material.

Powder Metallurgy consist of 4 processes Powder Manufacturing

Blending

Compacting

Sintering

1. Powder Manufacturing

The most commonly used methods are mechanical methods,

atomization, electrolysis etc.

Most commonly used powders are copper and iron based materials

Particle size ranges from 0.1 microns to several mm.

Blending Blending is done to get a homogeneous

mixture of powders. A mechanical mixer is used to blend the

powders of different materials.

Compacting Compacting is the process of

converting the loose powder into compact of required size and shape.

Powder is poured into the die. The dies are forced together

under pressure and it is compressed to desired .size and shape

Sintering

After compacting the product is heated in a furnaceto a temperature

close to the melting point of the base metal.

Heating causes the metal particles to sinter.

Sintering is done to achieve strength and hardness to the final

product.