• Design of punch and die is also difficult for number of operation (more than five). Compound die is excellent for two operations.
• The term compound die usually refers to a one-station die, designed around a common vertical centerline, in which two or more operations are completed during a single press stroke.
• Usually, only cutting operations are done, such as combined blanking and piercing.
• A common characteristic of compound-die design is the inverted construction, with the blanking die on the upper die shoe and the blanking punch on the lower die shoe.
• The pierced slugs fall out through the lower die shoe.
• The part or finished blank is retained in the female die, which is mounted on the upper shoe

Operations performed by a Compound die.

Compound Blank and Pierce Dies

• Compound dies are widely used to produce pierced blanks to close dimensional and flatness tolerances.
• Generally, the sheet material is lifted off the blanking punch by a spring-actuated stripper, which may be provided with guides to feed the material.
• If hand-fed, a stop is provided to position the strip for the next stroke.
• The blank normally remains in the upper die, and is usually removed by a positive knockout at the top of the press stroke.
• Ejection of the blank from the die by spring-loaded or positive knockout occurs at the top of the stroke. Because of this feature, the die does not require angular die clearance.
• Not providing angular die clearance both simplifies die construction, and assures constant blank size through the life of the die. Part Removal from Compound Dies
• A potential disadvantage of compound dies is that the part must be removed from the upper die at the top of each stroke.
• The part is usually knocked out at the top of the stroke by means of a press-actuated knockout bar.
• In the case of small parts, once knocked out of the upper die, they may be ejected by a timed blast of air.
• Larger parts can be removed by means of a shuttle unloader that enters the die opening as the ram ascends.
• The press ram normally drives the unloader, although air, hydraulic, or servo motor driven units may be used.
• Accomplishing positive part removal during each press stroke may limit the speed of the operation. For low production jobs, manual removal with appropriate safeguarding precautions may suffice.

Cut-and-Carry or Pushback Operations

• Cut-and-carry operations are very useful for producing parts with high flatness requirements.
• The cutting station in cut-and-carry dies is normally an upside-down compound die.
• The part is cut and then pushed back into the carrier strip rather than ejected.
• The feature of pushing the part back into the carrier strip or scrap skeleton provides a positive means to get the part out of the die without an auxiliary unloading means required with a conventional compound die.
• Cut-and-carry operations are useful stations in progressive dies.