In stamping production, every operation falls into one of two categories based on how the material deforms: separating operations and forming operations. Separating operations cut the sheet metal along a defined contour—blanking, piercing, trimming, and slitting all belong here. The key process parameter is clearance between punch and die; get it wrong and you will see excessive burr height, secondary shear cracks, or accelerated tool wear. Forming operations, by contrast, change the shape of the sheet without intentionally fracturing it—bending, drawing, flanging, and embossing are typical examples. For forming, the critical factors shift to material flow stress, blank holder force, and die radius. In mold design, mixing up these two categories at the quotation stage is a common source of underestimated tonnage and wrong die material selection.
Within these two broad categories, three core process steps deserve close attention on the shop floor. First, blanking and piercing: punch-to-die clearance typically runs 5–10% of sheet thickness depending on material—mild steel around 5–7%, stainless steel higher. Second, bending: springback compensation must be built into the die geometry, and bend radius should not fall below the material's minimum formability limit or you will get cracking on the outside fiber. Third, drawing: draw ratio, blank holder pressure, and lubrication all interact, and a poorly set blank holder force will produce wrinkles or tearing. In progressive die design, these three steps are often combined in one strip layout, so the sequencing and station spacing directly affect strip utilization and die cost. A practical rule from the tool room: verify clearance and springback on a tryout press before committing to production, because correcting a hardened die insert is far more expensive than adjusting a soft tryout tool.
For quoting engineers, classifying each operation correctly at the RFQ stage helps avoid the classic mistake of pricing a drawing job as a simple blanking job. Material grade, sheet thickness, and required tolerance all feed into the process choice, and that choice drives die structure, press tonnage, and cycle time. Getting the classification right early saves rework later. For more mold sourcing and process reference information, visit MoldSo at www.moldso.com.