How To Use Die Cuts

Effigy i
Compression trimming die design

Various specialty metal cut methods are used in stamping operations. Amid them are pinch, breakout, and shimmy.

Compression Trimming

Compression trimming is a special method in which the vertical walls of a drawn or stretched vessel are cutting by pinching the metal between two hardened tool steel die sections. In about cases, the clearance between the die sections is as little as possible (Figure 1).

Unlike a conventional metal cutting process, no shearing or fracturing takes place in pinch trimming. Items such as deep-drawn cans often are pinch trimmed.

Although pinch trimming is a very popular method, because the metal basically is pinched off, a very sharp burr usually remains on the part (Figure ii). This burr must oftentimes be removed by tumbling the parts in a tub containing abrasives.

Figure ii
Result of compression trimming

Pinch trimming also places a peachy load on the sides of the die sections, which results in high wear. Nearly pinch trimming operations require a great deal of maintenance.

Breakout Trimming

Breakout trimming is a specialty metal trimming procedure in which the metal is forced to fracture or break costless from the vessel'southward flange. If you are accustomed to conventional cutting operations, this process nearly certainly may look harebrained to you. Different a conventional metal cutting process, the lower die section has a 45-degree bending footing on its edge. This angle has two basic functions:offset, to allow the loving cup to fully nest in the lower die, and second,. to force the flange to bend upward slightly.

The cut clearance also is much greater in breakout trimming than the clearance commonly used in conventional cutting operations. This additional clearance causes leverage activeness, merely does not allow for the metal to exist bent into a vertical wall. However residue assured, this process works well, especially for metals that severely work harden (Figure three).

Figure 3
Break out trimming

Breakout trimming takes advantage of the metallic'southward work hardening and reduced thickness in a given localized zone. This method works best for round or centric symmetrical drawn parts.

For breakout trimming to work finer, the drawn cup must exist properly prepared for the process. The within radius on the cup'south flange must exist reduced to a expressionless sharp corner before using this method. This is accomplished by drawing the cup deeper in the drawing operation or compressing it back over a expressionless sharp corner on the die section (Figure 4). Doing so reduces thickness inthe radius and allows work hardening to take place.

Figure 4
Creating a minor radius

After the loving cup has been prepared properly, it can exist introduced into the breakout trimming procedure, in which the cup flange volition be forced upward, causing the metal to breakat the dead sharp corner (Figure v). Because the cup flange is round, every bit it is pushed upwards it is forced into radial compression. This compression works to your reward by forcing the loving cup to befractured out of the flange.

Breakout trimming does not produce a burr as large equally that produced past pinch trimming. Too, because the loads on the tool steel sections are minimal, the die requires less frequent maintenance. However continue in mind that this method can be used only in situations in which the metallic must exist cutting at the intersection of the flange and the cup'due south vertical wall.

Figure 5

Shimmy Trimming

Shimmy trimming is a unique metal trimming process in which a series of specially designed cams are used to force the part to motion side to side. Dissimilar conventional cam trimming, the part does not remain stationary, but rather moves horizontally in the die. It moves in such equally fashion that it can be trimmed true to the surface of the vessel. Trimming 90 degrees or true tosurfaceresults in a much cleaner cutting and considerably lower burrs than pinch trimming.

A great advantage of shimmy dies is that they can cut the entire perimeter of a part in a single press stroke. Unlike conventional pinch trimming, a shimmy trimming operation is not restricted to straight line cuts. Features such as notches, curved cuts, as well equally a various other cuts tin be made. Many common items such as cigarette lighters and gun shells are made using the shimmy trimmingprocess.

Figure 6
Parts trimmed with a shimmy trim die
Images courtesy of Vulcan Tool Corporation

Shimmy trimming operations also can exist designed to cutting metal as thick every bit 0.250 in. and, unlike conventional pinch trimming, can proceed the original metallic thickness in the trimmed area. Not similar conventional cutting operations, shimmy dies crave a pressure system such every bit a printing cushion or a nitrogen gas manifold (Figure half-dozen).

Which metal cutting performance a die design engineer chooses is based on many factors, including allowable burr tiptop, parts volumes, metal blazon and thickness, and trim line geometry. No unmarried trimming operation is best for all scenarios. The side by side article in this series will go along the give-and-take of metallic cutting.