In stamping, the first decision a mold engineer makes is classifying the operation by deformation type: separation or forming. Separation operations—blanking, piercing, and cutting—use the shear action between punch and die to fracture sheet metal along a closed contour. The controlling parameter here is blanking clearance. As a working rule, soft materials take 5%–8% of sheet thickness, while harder materials run 8%–12%. Clearance deviation directly affects burr height on the cut edge and tool life; run it too tight and you accelerate die wear, too loose and you fight secondary shear and heavy burrs. In practice, clearance is set per material grade and thickness, then verified on the first-off samples before production release.
Forming operations—bending, drawing, and flanging—rely on plastic flow rather than fracture, so the material must stretch without splitting. Two parameters dominate: elongation and springback compensation. For bending, springback must be built into the punch angle and die radius, otherwise part geometry drifts outside tolerance after unloading. For drawing, blank holder force and draw radius control material flow into the cavity; insufficient hold-down causes wrinkling, while excessive force thins the wall or tears the cup. Flanging follows similar logic—pre-pierced hole quality and edge distance determine whether the flange stretches cleanly or cracks. These are the details that separate a stable die from one that needs constant tweaking on the press.
From a tooling standpoint, the separation-versus-forming call also drives die structure: blanking dies prioritize shear edge strength and stripper design, while forming dies prioritize radius control, surface finish, and springback adjustment features. Getting the classification right up front saves weeks of trial-and-error. For more mold sourcing information and supplier comparisons, visit MoldSo at www.moldso.com.