IDEMI

While there are many die-cutting operations, some of which are very complex, they can all be reduced to the following simple fundamentals.

Fig. 4-1 Drop-through Blanking Die          Fig. 4-2 Piercing Die Assembly

   4.1.1 Plain blanking: Fig. 4-1 shows a simple operation of this type. The material used is called the stock and is generally a ferrous or nonferrous strip. During the working stroke the punch goes through the material, and on the return stroke the material is lifted with the punch and is removed by the stripper plate. The stop pin is a gage for the operator. In practice, he feeds the stock by hand and locates the holes to be punched as shown. The part that is removed from the strip is always the work piece (blank) in a blanking operation.

4.1.2 Piercing: This operation consists of simple hole punching. It differs from blanking in that the punching (or material cut from stock) is the scrap and the strip is the work piece. Piercing is nearly always accompanied by a blanking operation before, after, or at the same time. Fig. 4-2 shows a typical piercing die assembly.

4.1.3 Lancing: This is a combined bending and cutting operation along a line in the work material.  No metal is cut free during a lancing operation.  The punch is designed to cut on two or three sides and bend along the fourth side. Fig. 4-3 and 4-4 show the principle of the lancing operation.

Fig. 4-3 lancing action                Fig. 4-4 Strip lanced for free metal for forming

4.1.4   Cutting off and parting: A cutoff operation separates the work material along a straight line in a single-line cut (Fig. 4-5). When the operation separates the work material along a straight line cut in a double-line cut, it is known as parting (Fig. 4-6) . Cutting off to separate the work piece from the scrap strip. Cutting off and parting usually occur in the final stages of a progressive die. Cutting off is also used to chop up the scrap strip skeleton as it leaves the die. This makes the scrap much easier to handle.  Fig. 4-7 shows the basic principles of cutting off and parting.

Fig. 4-5 Cutoff action                Fig. 4-7 Layout for making blanks by Cutoff

4.1.5 Notching: This operation removes metal from either or both edges of the strip. Notching serves to shape the outer contours of the workspace in a progressive die or to remove excess metal before a drawing or forming operation in a progressive die. The removal of excess metal allows the metal to flow or from without interference from excess metal on the sides. Fig. 4-8 shows a typical example of notching

Fig. 4-8 Notching                                                 Fig. 4-9 Shaving

4.1.6   Shaving: Shaving is a secondary operation, usually following punching, in which the surface of the previously cut edge is finished smoothly to accurate dimensions. The excess metal is removed much as a chip is formed with a metal-cutting tool. There is very little clearance (close to zero) between the punch and die, and only a thin section of the edge is removed from the edge of the work piece. Fig. 4-9 described the shaving operation.

Fig. 4-10 Trimming a horizontal flange

4.1.7 Trimming: This operation removes the distorted excess metal from drawn or formed parts and metal that has been needed in a previous operation. It also provides a smooth edge. Fig. 4-10 shows tooling for Trimming a horizontal flange on a drawn shell in a separate operation. After scrap from a sufficient number of trimmed shells has accumulated, the piece of scrap at the bottom is severed at each stroke of the press by scrap cutter shown in this figure and falls clear.