Redistribution: Deforming

Redistribution: deforming

Redistribution

Casting, moulding

Die casting, injection moulding, extrusion

Redistribution

Redistribution refers to the fact that material is moved around in order to shape it into a product or component.

This can be done in one of two ways; 1. deforming and 2. reforming.

Deforming involves changing the shape of the material without changing the state. i.e. the material remains a solid throughout the shaping process even though it may be subjected to heat and/or pressure.

Wood is not a material that lends itself to being deformed as it is mostly used in its natural state and its strength resists bending.

Thermoplastic polymers can become soft at relatively low temperatures at which point they can easily be deformed.

Metals are also relatively easy to deform using a combination of heat and pressure.

Metal lends itself well to being deformed with pressure and heat.

Bending and folding

Metal can be bent cold or hot and sheet metal can be folded in similar way to sheet plastic, although it requires specialist high pressure machinery.

Spinning

Spinning is a process by which a disc of metal is rotated at high speed and formed into a symmetrical part.

Metal spinning does not involve removal of material, as in conventional wood or metal turning, but forming (moulding) of sheet material over an existing shape.

Commercial applications include rocket nose cones, cookware, gas cylinders, brass instrument bells, and public waste receptacles. Virtually any ductile metal may be formed.

Sinking

Sinking is a metalworking technique whereby flat sheet metal is formed into a non-flat object by hammering. While sinking is a relatively fast method, it results in stretching and therefore thinning the metal, risking failure of the metal if it is 'sunk' too far.

Sinking is used in the manufacture of many items, from jewellery to plate armour.

Punching

Punching is a metal forming process that uses a punch press to force a tool, called a punch, through the work piece to create a hole via shearing. The punch often passes through the work into a die. A scrap slug from the hole is deposited into the die in the process. Depending on the material being punched this slug may be recycled and reused or discarded. Punching is often the cheapest method for creating holes in sheet metal in medium to high production volumes. When a specially shaped punch is used to create multiple usable parts from a sheet of material the process is known as blanking.

Blanking and Piercing

Blanking and piercing are shearing processes in which a punch and die are used. The tooling and processes are the same between the two, only the terminology is different: in blanking the punched out piece is used and called a blank; in piercing the punched out piece is scrap. The process for parts manufactured simultaneously with both techniques is often termed 'pierce and blank'. An alternative name of piercing is punching (see previous slide).

Forging

Forging is a manufacturing process involving the shaping of metal using localized compressive forces. Forging is often classified according to the temperature at which it is performed: ‘cold’, ‘warm’, or ‘hot’ forging. Forged parts can range in weight from less than a kilogram to 580 metric tons. Forged parts usually require further processing to achieve a finished part.

Drop Forging

Drop Forging is a forging process where a hammer is raised and then ‘dropped’ onto the work piece to deform it according to the shape of the die. There are two types of drop forging: open-die drop forging and closed-die drop forging. As the names imply, the difference is in the shape of the die, with the former not fully enclosing the work piece, while the latter does.

Drawing

Drawing is a metalworking process which uses tensile forces to stretch metal. It is broken up into two types: sheet metal drawing and wire, bar, and tube drawing. The specific definition for sheet metal drawing is that it involves plastic deformation over a curved axis. For wire, bar, and tube drawing the starting stock is drawn through a die to reduce its diameter and increase its length. Drawing is usually done at room temperature, thus classified a cold working process, however it may be performed at elevated temperatures to hot work large wires, rods or hollow sections in order to reduce forces.

Deep Drawing

Deep Drawing is a sheet metal forming process in which a sheet metal blank is radially drawn into a forming die by the mechanical action of a punch. The process is considered ‘deep drawing’ when the depth of the drawn part exceeds its diameter.

This is achieved by redrawing the part through a series of dies. This is the process used to make most aluminium drink cans.

Press Forming

Press Forming is a sheet metal process that uses a pair of tools called a ‘die’ mounted inside a press and then the metal is placed inside the die. The press then applies high pressure (3000 tons of force or higher on large presses) and the material is formed to match the shape of the die. In other words, press forming is a forming technology where a pressing force is applied to a material to deform it (by bending, stretching, etc.) to match the size and shape of the die, and the material then maintains that shape forever. It is used to make the cases for white products such as fridges and most car body parts are made by press forming nowadays.

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