When we talk about stamping, the first thing to get right is the tonnage match between press and die. A common rule on the floor: required tonnage = blanking perimeter × material thickness × shear strength × safety factor (typically 1.3). For a 2 mm cold-rolled steel bracket with a 400 mm blanking perimeter and shear strength around 350 MPa, that puts you near 36 tons before the safety factor — so a 63-ton press is the realistic minimum, not a 40-ton. Ignoring this is how you crack a die block or mushroom a punch on the first hit. Die clearance matters just as much: for mild steel, 8–12% of thickness per side is a solid starting point, tighter for fine blanking, looser for thick-gauge work where burr height is less critical.

Die design details decide whether the process runs for 100,000 strokes or fails at 5,000. Guide pillar clearance should be tighter than punch-to-die clearance — otherwise the guides wear before the cutting edges do. For progressive dies, the strip layout must account for pilot holes engaging before the punches contact the material; a 1–2 mm lead on the pilot is not optional. Ejector springs should be sized so that stripping force exceeds the friction between part and die wall, usually 5–10% of blanking force. And on the press side, check parallelism between the bolster and ram face — 0.05 mm/m is the practical limit before you start seeing uneven wear on one side of the die.

During tryout, start with a soft material like aluminum or mild steel at 60–70% of target tonnage, then step up. Watch for slug pulling — if slugs ride up with the punch, increase clearance slightly or add a shear angle. Measure burr height across the cut edge; if it exceeds 5% of thickness, the clearance is too large. For more die design references and supplier sourcing, visit MoldWorld at www.moldw.com.