FORMING OPERATIONSby

Waqas ahmed

Forming operation Forming process make use of suitable stresses

like compression, tension, shear or combined stresses to cause plastic deformation of the materials to produce required shapes. In forming, no material is removed i.e. they are deformed

Some of the forming processes are:ForgingExtrusionRollingDrawing

Forging process

Forging is a manufacturing process involving the shaping of metal using localized compressive forces.  

Forging process

Introduction

A metal is shaped by compressive forces Oldest metal working process – 4000BC Can be performed with a hammer and anvil Typical forged products:

Bolts Rivets Connecting rods Gears

Lading-gear components for the C5A and C5B transport aircraft, made by forging. Steps involved in forging a bevel

gear with a shaft.

Grain Structure

Parts have good strength High toughness Forgings require additional heat treating

Fig : A part made by three different procedures, showing grain flow (a) casting (b) machining (c) forging

Open-Die Forging

Is the simplest forging process Sizes can very from very small parts to very large parts

Impression-Die & Closed-Die Forging

The workpiece acquires the shape of the die cavities while being forged between the two shaped dies

Precision ForgingPrecision Forging

Used for economic reasons The part formed is close to the final dimensions Less machining is needed Higher capacity equipment is needed Aluminum and Magnesium alloys work well in the process

CoiningCoining Closed-die forging process

Used for minting coins, medallions, & jewelry Lubricants can not be used in coining Can be used to improve surface finish

Extrusion process

Extrusion  is a manufacturing process used to create objects of a fixed cross-sectional profile. A material is pushed or drawn through a die.

Extrusion process

Rolling process

In metalworking , rolling is a metal forming process in which metal stock is passed through a pair of rolls.

Rolling process

Drawing process

Drawing is a metal working process which uses tensile forces to stretch metal. ...Cold drawing is primarily used in manufacturing plastic .

Drawing process

Sheet metalThe success of forming is in relation to two things, the flow and stretch of material. As a die forms a shape from a flat sheet of metal, there is a need for the material to move into the shape of the die. The flow of material is controlled through pressure applied to the blank and lubrication applied to the die or the blank. If the form moves too easily, wrinkles will occur in the part. To correct this, more pressure or less lubrication is applied to the blank to limit the flow of material and cause the material to stretch or thin. If too much pressure is applied, the part will become too thin and break. Drawing metal is the science of finding the correct balance between wrinkles and breaking to achieve a successful part.

Deep drawingMain article: Deep drawingSheet metal drawing becomes deep drawing when the workpiece is drawing longer than its diameter. It is common that the workpiece is also processed using other forming processes, such as piercing, ironing, necking, rolling, and beading.

Bar, tube & wireBar, tube, and wire drawing all work upon the same principle: the starting stock drawn through a die to reduce the diameter and increase the length. Usually the die is mounted on a draw bench. The end of the workpiece is reduced or pointed to get the end through the die. The end is then placed in grips and the rest of the workpiece is pulled through the die.[1] Steels, copper alloys, and aluminium alloys are common materials that are drawn.[3]

Drawing can also be used to produce a cold formed shaped cross-section. Cold drawn cross-sections are more precise and have a better surface finish than hot extruded parts. Inexpensive materials can be used instead of expensive alloys for strength requirements, due to work hardening.[4]

Plastic drawingPlastic drawing, sometimes referred to as cold drawing, is the same process as used on metal bars, but applied to plastics.[6]

Cold drawing is primarily used in manufacturing plastic fibers. The process was discovered by Julian Hill in 1930 while trying to make fibers from an early polyester.[7] It is performed after the material has been "spun" into filaments; by extruding the polymer melt through pores of a spinneret. During this process, the individual polymer chains tend to somewhat align because of viscous flow. These filaments still have an amorphous structure, so they are drawn to align the fibers further, thus increasing crystallinity, tensile strength and stiffness. This is done on a draw twister machine.[7]

[8]

For nylon, the fiber is stretched four times its spun length. The crystals formed during drawing are held together by hydrogen bonds between the amide hydrogens of one chain and the carbonyl oxygens of another chain.