Stamping uses a press and die to apply external force to sheet, strip, tube, or profile material, causing plastic deformation or separation to obtain the required shape and dimensions. For mold engineers, the value of watching a stamping animation is not the motion itself but the interaction between punch-die clearance and the matching of blanking force to stripping force. Take blanking of 0.8 mm cold-rolled sheet: the double-sided clearance is typically set at 8%–12% of material thickness. Too small a clearance produces high burrs and accelerated die wear; too large a clearance causes obvious rollover and a poor shear zone. In practice, the die is first machined to the theoretical clearance value, then fine-tuned based on the cut-edge quality during tryout—this step cannot be skipped.
From a mold-making standpoint, clearance control starts long before the press runs. The punch and die insert fit, guide-pin tolerance, and heat-treatment distortion all affect the actual clearance at the cutting edge. For a 0.8 mm cold-rolled sheet with a 0.064–0.096 mm double-sided clearance, even 0.01 mm of misalignment between punch and die can shift the local clearance enough to change burr height and tool life. This is why die builders should verify clearance with lead wire or feeler checks after assembly, not rely solely on drawing dimensions. The same logic applies to stripping force: if the stripper plate pressure is insufficient, the strip will lift with the punch and disrupt feed accuracy; if excessive, it can mark the part surface.
Blanking force and stripping force must be matched to the press capacity and the die structure. A common shop-floor rule is to keep blanking force within 70%–80% of rated press tonnage, leaving margin for shock loads and material thickness variation. For higher-strength sheet or thicker stock, the clearance range should be shifted upward and the die edge reinforced with a suitable insert material and corner radii. These are not theoretical refinements—they directly affect burr height, die maintenance intervals, and part consistency. For more mold sourcing information, visit MoldSo at www.moldso.com.