Forging and forming
Metal stamping and deep drawing: what goes wrong and where to inspect
Brackets, housings, panels and cups produced in progressive, transfer or tandem press lines. Tool condition and material properties decide almost everything.
01How the process works
Stamping cuts and forms sheet metal in press tools: blanking, piercing, bending, forming and drawing. Deep drawing pulls the sheet into a die to make cups and shells, thinning the wall. Progressive tools perform many operations in sequence as the strip advances.
Defects arise from tool wear, sheet material variation and press set-up. Burr height, splits, wrinkles, springback and hole position are typical acceptance features, often checked on dedicated gauges in high volume production.
- Coil and material. Material grade, thickness and properties verified.
- Tool set-up. Tool mounted, die height and feed set.
- Pressing. Blank, pierce, form, draw in sequence.
- Secondary operations. Tapping, welding nuts, deburring.
- Inspection and packing. Gauge checks, visual, packaging.
02What typically goes wrong
| Defect | Typical cause | How it is found |
|---|---|---|
| Splits and necking | Material ductility, draw depth, lubrication | Visual, thickness check |
| Wrinkles | Blank holder force | Visual |
| Burrs | Tool wear, clearance | Burr height measurement |
| Springback | Material strength variation | Gauges, CMM |
| Missing or misplaced holes | Broken punch, feed error | Check fixture, in-die sensors |
| Scratches and slugs marks | Slug pulling, dirt | Visual |
03Where an inspector should look
Before production
- Tool approval and capability
- Material certificate and formability
- Check fixture validation
During production
- First off and last off parts
- Punch and die condition
- Burr height trend
After production
- Gauge or CMM checks
- Surface class inspection
- Packaging and corrosion protection
04Standards and references
EN 10130 and EN 10346 (sheet steels), EN 10149 (high strength cold forming steels), DIN 6930 (stamping tolerances).
Standards are named for orientation. The applicable edition and acceptance criteria are those in your contract and specification.