4.10 Stamping

Stamping or sheet stamping is a cold method of the plastic metal working. A strip or a tape may be used as a billet (half-finished article). Such parts as a watch hand, car bodies, rocket shells are manufactured using stamping.

Stamping provides high productivity: sometimes, a part per second. Alloys of high plasticity (Cu, Al, Mg, Ti) low carbon steel, plastic, leather and other materials undergo stamping.

All stamping operations are carried out by special tools and machines (stamps and presses).

Stamping operations may be classified as forming and separating.

The separating operations are used for cutting of a sheet in tapes and pieces by shears. The shears may be of three main types: straight-blade, guillotine and circle shears (Fig. 4.26).

Fig. 4.26. Separating operations of sheet stamping: a-cutting by guillotine shears;

b-cutting by circle shears; c-blanking; d-piercing; e-notching; 1 – upper knife; 2 – lower knife;

3, 8 – billet; 4 – size restrict; 5 –fixer; 6 – lower die; 7 – upper die; 9 – part (stamping); 10 – waste

Length of the cutting line for straight-blade and guillotine shears is not in excess than horizontal length of the shears L.

The length of the cutting line (of the tape) is not limited when the circle shears are used. The cutting out (blanking) and piercing are making external and inner contours of a part, correspondingly.

Forming operations are plotted in Fig. 4.27.

All these and other operations are made by dies of complex construction. Stamps consist of upper dies, bed dies, upper and bed plates, columns, bushings, springs and other parts. Upper plate is fastened to plunger of a press, bed plate is fasten to a table of the press.

Fig. 4.27. Forming operations of sheet stamping: a-straightening; b-bending; c, d, e-draw-forming,

f-spread forming, g-flanging; 1 – upper die (punch); 2 – lower die; 3 – billet.

5 Welding

Welding is a technological method of manufacturing of permanent joints and facing the surfaces of parts if required. Parts of various materials may be welded. Welding is carried out in the air or other gases and vapors, under water, in vacuum.

The first welding method was found 4...5 thousand years ago, when man produced iron from iron ore in open fire, using charcoal as a fuel and reducer. During hammering to remove residual charcoal the pieces of iron were joined with each other. This was blacksmith, or forging (hammer) welding.

Then man noticed that during hammering at room temperature two pieces of gold (it possesses high plasticity) might be joined too. This was a cold welding. It happened approximately 3 thousand years ago.

Approximately at this time the foundry welding was introduced into practice. It was performed in the following way: liquid metal (brass) was poured between two brass parts and welded them together.

These three methods of welding have been used for long time and only in 1882 Russian engineer M. Benardos suggested arc welding with non-consumable carbon electrode.

In 1888 Russian scientist N. Slavjanov worked out a method of the arc welding with metallic (consumable) electrode. In 1902 gas welding was suggested in France. So, the application of welding has rapidly expanded in the recent 100 years. About 60 welding methods are employed now.