What is a servo press?

A servo press uses servo motors for precise force and position control during forming operations.

How do I calculate servo press tonnage?

Use our free tonnage calculator at servopress.club/tonnage-calculator.html

Servo Press for Stainless Steel Cookware: Deep Draw Setup

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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.

dave_toolmaker

304 SS cookware drawing is all about the blank holder. Too much pressure and the flange locks up and the punch tears through the bottom. Too little and you get wrinkles. On a servo press, I program a decreasing blank holder force through the stroke —start at 35% of draw force and reduce to 20% as the cup deepens. This follows the material's work hardening curve.

yuki_rnd

The draw ratio limit for 304 SS is about 2.0 for the first draw (blank diameter / punch diameter). For deeper cookware like stockpots, you need multiple draws with intermediate annealing. The servo press advantage: you can do a partial draw and redraw in the same stroke using a compound die with the right motion profile. Eliminates one press operation.