Manufacturing of parts cannot be absolutely precise. If such be the case, the cost of components would be horrendous. Different manufacturing fields use a different tolerance ranges. Where ±0.031 in.(0.79mm) can be unacceptable in die work, the same tolerance range is too tight for, let us say, in steel constructions.
Components and assembly
A stamping die, as mounted in the press, is a complex-action mechanism, producing parts in predetermined sequence. The lower half of the die, mounted on the lower die shoe, is firmly attached to the press bed, while the upper portion is bolted to the ram, sliding up and down along with it.
Aside from an upper and lower die shoe, every stamping die consists of several other blocks, which hold or support the punches, dies, bushing, inserts, and other elements.
The stamping die has several piercing punches with the last punch with the last punch being the blanking station. All punches are assembled into a block called a punch plate, which is separated from the upper die shoe by a backup plate. Backup plates are made of hardened steel, usually 3/8 in.(10mm) thick, with a 1/2 in. (15mm) exception for heavy work.
The stripper prevents the piercing from sticking to punches. It also restrains the rest of the strip from moving along with the upper half of the die by keeping it positioned on the face of a die block.
The stamping die block contains all bushings, forming dies, or cutting inserts. It is supported by another backup plate positioned between this block and the lower die shoe.
Mounting the dies
All the punches and dies described earlier are assembled with their respective blocks. The blocks themselves are firmly and with great precision attached to their supporting backup plates(where used) and to their die shoes. For mounting of blocks, socket head cap screws are most often utilized. The precision alignment is achieved by at least two dowel pins per block.
Usually, with smaller blocks, four screws and two dowel pins will suffice. With larger blocks, six or more screws and four dowels should be used.
Machining of blocks
All the material to be removed in order to produce holes in the blocks has to be drilled away in stages. It is not possible to take a 5/8 in. (16mm) diameter drill and drill a 5/8 in.(16mm) diameter opening in one pass. This may be done in wood or in other soft material, but certainly not in metal and especially not in tool steel.
All blocks are secured together with the aid of screws, the choice most often being socket head cap screws. With spring-and-bolt arrangements, shoulder screws are usually used to support the spring against misplacement or buckling with its shank, hold the spring-loaded block with its threaded portion, and control the length of the movement with the location of its head in the clearance pocket.
Jig and fixtures
Jig and fixtures can be considered a part of die building and die making, and almost every toolmaker displays a distinct ingenuity in devising and using them. Most often, jigs and fixtures are used to clamp down various parts, hold down the blocks, and so on.
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