Progressive Dies

Dies that produce parts requiring more than one forming operation, worked in sequence at separate stations, are called progressive dies (progressive mold / progressive die stamping).

In progressive dies, each processing stage of the part being produced is completed at a separate station. In some cases, empty (idle) stations can be included within the die. This prevents the female die from being weakened and makes assembling the punches easier. However, this increases the length of the die set.

Progressive dies are generally used when mass production volume is very high and the cost of the part to be produced is low. Otherwise, designing and building a progressive die for stamping parts with low production quantities will increase the cost of the die as well as the cost of the stamped part.

The figure above shows the stamping positions on the strip material for a part produced in a simple pierce, blank, and part-off progressive die.

Design of Progressive Dies

The person designing a progressive die must demonstrate their knowledge and skill, and should also draw on previously built progressive die designs along with their own experience.

The following process steps should be kept in mind when designing progressive dies.

1- The sheet material thickness should not be too small.
2- Die set dimensions suited to the available press machine should be chosen.
3- The total forming force must not exceed the tonnage of the available press machine.
4- Pilot holes and notches used for guiding purposes should be placed at the first station, and other piercing, blanking, bending, drawing, and similar operations should be done at subsequent stations.

5 — The strip material used for drawing or forming operations should be prepared to the appropriate dimensions.

6 — If a part requires a large number of piercing operations, these operations should be distributed across several stations.

7 — In simple pierce-and-part-off progressive dies, to increase the female die area, piercing should be designed at the first station, an idle second station, and the part-off operation at the third station (Figure 10.11-b).

8 — An idle station should be included to ease the movement of the strip material and increase the strength of the female die, stripper, and punch plates.

9 — The rolling direction of the strip material should be indicated.
10- Whether the drawing or forming operation will be in the downward or upward direction should be designed in advance.

11- Depending on the shape of the part being produced, any other operations preceding the cutting operation must be clearly specified.

12 — The strip-material feed mechanism should be selected to suit the die design.
13 — To minimize material waste, the strip layout plan should be prepared in several different configurations.
14 — The cutting or forming area suited to the press force must be specified.

The strip material layout for the part to undergo progressive stamping operations is prepared in advance and applied directly to the female die. The figure above shows a cross-sectional view of the die illustrating the progressive stamping operation, with the strip material layout along with the produced parts shown below it.