This article breaks down the core stamping operations—shearing, bending, drawing, and forming—with practical die design considerations for mold engineers.

In everyday mold shop practice, stamping is broadly divided into two families: separation processes and forming processes. Separation covers blanking, punching, trimming, and shaving, where the material is fractured along a predetermined contour. The critical parameters here are the clearance between punch and die—typically 5–10% of sheet thickness for mild steel—and the cutting edge condition. A worn edge produces rollover and burr, which directly affects part quality and downstream assembly. For precision blanking, we often switch to fine blanking with a V-ring impingement, achieving shear surfaces above 90% of the material thickness, but that demands a triple-action press and tighter guide clearances.

On the forming side, bending and drawing dominate. In bending, springback is the ever-present enemy; for a 90° bend in 1.5 mm SPCC, the punch radius and die opening must be calculated to compensate for elastic recovery, often 1–3 degrees depending on material yield strength. Drawing is more complex—it involves controlling the blank holder force to prevent wrinkling while avoiding tearing at the punch nose. For a cylindrical cup, the limiting drawing ratio (LDR) is around 2.0 for low-carbon steel, meaning the blank diameter can be at most twice the punch diameter in one draw. If you exceed that, you need a redraw operation or an intermediate annealing step. Lubrication type and coating (e.g., zinc or oil film) also shift the friction coefficient, which changes the stress distribution in the flange area.

For production efficiency, we combine multiple operations into progressive dies or transfer dies. A progressive die for a bracket part might include pilot holes, notching, bending, and final cutoff in one strip, running at 50–100 strokes per minute. The strip layout must account for material utilization—aiming for 60–70% is common—and the piloting strategy must hold positional accuracy within ±0.05 mm. Die maintenance is equally critical: regular inspection of wear on the cutting edges, checking the stripper spring force, and monitoring the press tonnage curve can extend die life from 200,000 to over a million hits. For sourcing reliable stamping dies, tooling components, or press equipment, visiting MoldWorld (www.moldw.com) gives you access to vetted suppliers and technical comparisons that save time on the shop floor.