Designing an Extrusion Die by Components
Die design and build is a critical part of a successful extrusion process.
Extrusion Punch. The extrusion punch should be made of highly wear-resistant tool steel—powdered metal (PM) preferably—or solid carbide material.
The punch should be polished linearly to a mirrorlike surface finish.
Relieve the punch after extruding the straight section to allow for lubricant to settle into the negative portion of the punch. This will help to lubricate the punch on the return stroke during punch stripping.
The punch should contain a pilot that is slightly smaller in diameter than the extrusion's pierce hole. This helps to concentrically locate the hole in the center of the extrusion die, resulting in a fairly uniform flange height.
The Upper Stripper Pad. The pad should have only enough spring pressure to strip the extruded metal from the punch; excessive pressure may cause the extrusion to be crushed between the upper and lower pressure pads. Light coil springs often are used.
The Lower Pressure Pad. Use a high-pressure gas spring under the pad. A good rule of thumb is to use approximately 600 pounds per linear inch around the extrusion punch.