Compound Dies

Dies that produce parts requiring more than one forming operation in a single operation and at the same station are called compound dies.

The part produced with these dies does not fall down through the die opening and remains inside the die. The part, which is pushed down into the die with the help of an ejector pin or plate, is removed from the die together with the strip scrap skeleton.

Multiple Operations in One Stroke

Compound dies perform multiple manufacturing operations (cutting, bending, etc.) simultaneously in a single stroke of the press.

High Production Speed

Compound dies significantly increase production speed and efficiency compared to working with separate dies.

High Design Complexity

The design and manufacture of compound dies is far more complex and costly than single-function dies.

Pierce-Blank Compound Die

Dies used to produce parts such as washers and similar parts with holes are called pierce-blank compound dies. In low-tonnage dies, spring-loaded plates, ejector pins, stripper plates, and similar die elements are used.

In high-tonnage compound dies, a pneumatic or hydraulic system is also used for the moving die elements such as the pressure plate, ejector pin, and ejector plate. In this way, all moving die elements are operated by the pneumatic or hydraulic system.

pneumatically operated washer die — A compound washer die operated by compressed air (pneumatic)

1 — Upper die plate
2 — Female die
3 — Ejector (knockout) plate
4 — Piercing punch
5 — Punch plate
6 — Spacer plate
7 — Ejector pin
8 — Locating pin
9 — Die shoe/frame
10 — Limiting piston

11 – Stripper finger
12 – Stripper finger segment
13 – Punch guide plate
14 – Blanking punch
15 – Ejector pin
16 – Ejector pin plate
17 – Ejector pin support plate
18 – Spacer disc
19 – Plug
20 – Guide post

compound die washer die — Spring-loaded special compound washer die, forming position

Cut-Bend-Draw Compound Dies

Lance-pierce-part-off compound die

The lance-pierce-part-off compound die is shown in the figure below. As the die begins to close, the lancing punches also begin cutting the channel into the strip material. When the lancing operation is 2/3 complete, the parting punch separates the part from the strip material. While the lancing of the part still remaining in the die is being completed, the piercing punches simultaneously pierce the holes. When the die opens, the formed part is ejected with the help of the ejectors.

Part-off and forming compound die

The figure below shows a part-off and forming compound die. Two punches are mounted on the upper die plate. One of these is the parting punch; the other is the pad punch and forming punch, assembled so they can move telescopically within one another. The pad punch, which performs the U-bend, is mounted to the forming punch so it can move along its own axis without obstructing the bending operation.

The forming punch, which carries the pad punch on it, has spring-loaded holders on its front and back faces and centering pins on its face. It releases the pad punch at the moment of forcing.

The female die mounted on the U-die is hinged. As the U-die moves downward, the hinged female die closes; when the die opens, the U-die, which moves upward under spring pressure, opens the hinged female die. The part taken from the opened die is flexed slightly to remove the pad punch from inside it.

Strengths and Weaknesses of Compound Dies

Strengths

1 — Because mass production is high, the cost per formed part is low.
2 — Since it does the work of multiple dies alone and at the same station, setting it up on the press is not time-consuming.
3 — Since it doesn’t require a large number of press machines, die design is easier relative to the existing press machine.

Weaknesses

1 — Designing and building the complete die is time-consuming.
2 — The die is difficult to repair.
3 — Die cost is high.
4 — Because it requires maximum forming force, it’s difficult to find a high-tonnage press machine.