Perforation is generally the most severe operation performed in a die. That’s because the punch press applies forces ranging from a few tons to more than 1000 tons. Proper press alignment is essential. While die set has some effect on alignment during operation, it cannot offset poor press alignment.
A simple die typically perforates holes in a part or blanks out the part using punches in conjunction with mated lower die components (matrixes). Simple dies also commonly produce basic forms as well as perform notching and lancing operations.
Simple dies require a press operator to load and unload parts and part material before and after each press cycle.
A compound die blanks and perforates a part at the same time in the same station. In most cases this operation perforates a hole or holes down, while the part blanks up. This allows slugs from those holes to fall through the die. This method leaves the part in the die, requiring some means of part removal.
Compound dies commonly run as single-hit dies. They can run continuously with a feeder, provided you can remove the part in a timely manner. Open Back Inclinable (OBI) presses – in the inclined position along with an air blowoff – aid in part removal.
Advantages of a compound die include:
• Minimal space in the press
• All burrs in one direction
• Superior accuracy between holes and trim edges
• More economical to build than a progressive die
A disadvantage of a compound blank die is its limited space that tends to leave die components thin and weak. This concentrates the load and shock on punches and matrixes, resulting in tooling failures.
Progressive dies provide an effective way to convert raw coil stock into a finished product with minimal handling. As material feeds from station to station in the die, it progressively works into a completed part.
Progressive dies usually run from right to left. The part material feeds one progression for each press cycle. Early stations typically perforate holes that serve as pilots to locate the stock strip in later stations.
There are many variations of progressive die designs. The design shown here illustrates some common operations and terminology associated with progressive dies.