SOME OTHER FORMING PROCESSES

Trimming: The excess metal which remains around parting lines or around other edges after previous operations, such as forging, die casting, and drawing of sheet metal parts is removed by ‘trimming’. Trimming dies are similar to blanking dies and the parts are forced through the die by suitable punch.

Shaving: A very small amount of metal (about 10% of the metal thickness) is removed or ‘shaved’ from blanked or pierced edge in order to obtain edges which are smooth, square, and within closer dimensional tolerances. The parts to be shaved are placed in a locating recess above the die opening and during the downward stroke of the punch, the edges are shaved as the part is forced through the die.

Notching: Notching is the cutting of relatively small indentations in the edge of workpieces. A rubber, used for only small quantities of workpieces, is designed to remove, by a notching action, some metal form an edge of a workpiece.

Embossing: The production of raised or projected designs is relief on a surface is known as ‘embossing’ sheet metal may be embossed between two matching die halves.

Coining: Coining consists of placing a proper amount of metal within a confined die space and exerting sufficient pressure to cause the metal to flow to all properties of the die cavity. The metal is caused to flow in directions perpendicular to the corresponding force along the die surfaces. Since lubrication is not used when good impression details are required, the compressive force required may be enormous.

Peening: This method is employed to set up a superficial state of surface compressive stress, causing the interior of the member to assume an opposite tensile stress. Because fatigue generally occurs from surface cyclically loaded in tension, the useful lives of such member are frequently extended by shot peening.

Hobbing: It is a method of making moulds for the plastic and die casting industries. A punch from tool steel to the shape of the cavity, heat treated for hardness, and polished. It is then pressed into a blank of soft steel; if one hob properly applied it can make a number of cavities in one mould or in more than one mould.