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## Material Challenges
304 stainless steel (the most common cookware material) work-hardens rapidly during forming. This means:
- Forming force increases as the draw progresses
- Risk of splitting increases in later draw stages
- Multiple draws with annealing between stages are often required
## Single-Draw vs Multi-Draw
For a typical pot (diameter 200mm, depth 100mm, draw ratio 0.5):
- Single draw: possible with servo press using slow speed and high blank holder force
- Two-draw: more reliable, better surface finish, less risk of splitting
## Servo Press Setup for Single Draw
**Blank holder force:** 25-35% of forming force for 304 stainless.
**Forming speed:** 20-40mm/s. Slower than steel because stainless work-hardens faster.
**Dwell at BDC:** 100-200ms. Reduces springback and improves dimensional consistency.
**Lubrication:** Heavy-duty drawing compound with EP additives. Apply to both blank surfaces at 4-6 g/m2.
## Die Design Notes
- Punch radius: minimum 4x material thickness (too small causes splitting)
- Die radius: 6-8x material thickness
- Die clearance: 110-115% of material thickness (slightly more than steel to reduce friction)
- Die material: D2 or M2 tool steel, polished to Ra 0.4 μm
## Quality Issues
**Orange peel surface:** Blank holder force too high, or material grain size too large. Reduce blank holder force 10%.
**Wrinkling in flange:** Blank holder force too low. Increase 10%.
**Splitting at punch radius:** Punch radius too small, or forming speed too high. Increase radius or reduce speed.