Every stamping job starts with a simple truth: a flat blank is not a finished part. The moment the punch descends, the sheet metal undergoes a complex sequence of elastic and plastic deformation, and the toolmaker’s job is to control that sequence rather than fight it. The core parameters—clearance, bend radius, and blank holder force—are not arbitrary numbers. For mild steel, a typical die clearance of 10–12% of material thickness per side keeps the shear zone clean and minimizes burr height. Go tighter, and you risk excessive tool wear and galling; go looser, and you get rollover and a ragged edge. Similarly, the minimum bend radius for most low-carbon steels is about 0.8 to 1.0 times the sheet thickness. Below that, the outer fibers crack, and you’ll see micro-tears that can propagate during subsequent forming or assembly.

But the real challenge is springback. After the punch withdraws, the material tries to return to its original shape, and the amount of angular recovery depends on yield strength, thickness, and the bend’s severity. For a 2 mm thick DP600 sheet bent to 90°, expect springback of 3–6 degrees—sometimes more if the tooling is worn. The practical fix is not just overbending; it’s compensating the die geometry with a slight convex relief on the punch face and adding a coining step at the bottom of the stroke. This localizes plastic flow and sets the grain structure, reducing elastic recovery. In progressive dies, I also recommend adding a restrike station after trimming, because the cut edge’s residual stress can pull the part out of tolerance if you don’t. And never forget the blank holder: for deep draws, the force should be 20–30% of the total forming load, tuned so the material flows without wrinkling but still stretches enough to avoid thinning below the critical 15% reduction limit.

Finally, think about lubrication and press speed. A chlorinated or polymer-based drawing compound reduces friction at the die radius, but over-lubrication can cause the blank to slip and shift, leading to uneven wall thickness. On a mechanical press, the slide speed at the bottom of the stroke is nearly zero, which helps for coining but hurts for high-speed blanking—so match the press type to the operation. For short-run prototypes, try a hydraulic press with adjustable dwell; for production, a crank press with a counterbalance is more consistent. If you’re sourcing dies or evaluating a new stamping line, always ask for the material certificate and the press’s tonnage curve—they tell you more than any simulation. For more practical mold sourcing and tooling advice, visit MoldWorld at www.moldw.com.