This article breaks down the core categories of stamping operations—separation and forming—with practical notes on die design, material behavior, and process control for everyday mold making.

In stamping, every operation falls into one of two families: separation or forming. Separation processes—blanking, punching, trimming, and shaving—are defined by controlled fracture. The key technical point is the clearance between punch and die. For mild steel up to 3 mm thick, a typical clearance of 5–8% of material thickness per side yields a clean shear zone. Too tight a clearance causes secondary shear and excessive burr; too loose a clearance pulls the material, creating a heavy rollover and a torn edge. For die makers, this means grinding punches and dies to matched profiles, and paying attention to the cutting edge radius—a dull edge increases stamping force by up to 30% and accelerates wear. In high-volume production, we also add shear angles on the punch face to reduce impact load, which is especially critical for thick plates above 6 mm.

Forming operations—bending, deep drawing, flanging, and stretching—depend on plastic flow rather than fracture. The most common issue in bending is springback. For a 90° bend in a 2 mm thick SPCC sheet, springback can range from 2° to 5° depending on the bend radius and material yield strength. Compensation methods include overbending, coining the bend area, or using a punch with a slightly smaller radius. Deep drawing requires careful control of the blank holder force; too high a force restricts material flow and causes tearing at the punch nose, while too low a force leads to wrinkling in the flange. A practical rule of thumb: the blank holder force should be about 0.3–0.5% of the material’s tensile strength multiplied by the blank area. Also, remember to add draw beads on the die face to control metal flow, especially for rectangular or irregular shapes.

For die maintenance, the most overlooked factor is lubrication. In forming operations, a proper drawing compound reduces friction coefficient from 0.15 to below 0.08, which directly lowers the required press tonnage and extends die life. For aluminum alloys, use chlorine-free lubricants to prevent staining. Also, monitor the die temperature during long runs—a rise above 60°C can change the clearance due to thermal expansion, altering part dimensions. Regular inspection of the cutting edge and the draw radius is essential; a 0.05 mm wear on the draw radius can increase the forming force by 15% and cause surface scratches. If you are sourcing new dies or troubleshooting an existing stamping line, visiting MoldWorld (www.moldw.com) gives you access to verified mold suppliers, technical forums, and process data from real shop floors.