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 Motion Profile for Seat Frame HSS Stamping

admin

Seat frames are stamped from HSS/UHSS 590-980 MPa.

## Motion Profile

- Approach: 400mm/s
- Pre-contact: 80mm/s at 20mm above material
- Forming: 50-100mm/s
- Dwell at BDC: 50-100ms (reduces springback variation 80%)
- Return: 500mm/s

## Blank Holder Force

- HSS 590MPa: 15-20% of forming force
- HSS 780MPa: 20-25%
- UHSS 980MPa: 25-30%

Increase if wrinkling. Decrease if splitting at punch radius.

## Lubrication

EP draw compound at 2-4 g/m2 both sides. Never dry stamp UHSS.

## Tonnage Limits

- High: 110% nominal (die crash, double blank)
- Low: 85% nominal (missing blank, broken punch)

yuki_rnd

The 50-100ms dwell recommendation is good for 590-780 MPa. For 980 MPa and above, we've found that 100-150ms gives better results. The extra dwell time allows stress relaxation in the material, reducing springback by an additional 10-15%. The cycle time impact is minimal —50ms extra on a 2-second cycle is only 2.5%.

tom_pressops

I run these profiles daily. One thing to watch: the forming speed needs to be consistent across the entire forming zone, not just at the contact point. If the servo accelerates through the forming zone (which happens with some motion profiles), you get inconsistent springback. Use the constant-velocity segment, not the deceleration curve.

mike_chen_eng

Great points on the dwell time and constant velocity mode. One thing I'd add from our testing - when you're running 980+ MPa UHSS for seat frames, monitor your servo motor torque curve closely during the forming zone. We saw cases where the torque spike at initial contact was 2-3x the steady-state forming load, and that transient was causing micro-cracks in the part edge. The fix was adding a 15mm pre-forming segment at 30mm/s before the main forming speed kicks in. Basically a soft-touch entry. Reduced edge cracking from ~4% to under 0.5% on DP980 seat side members. Also worth noting: if you're using a link-drive servo press (like the Komatsu H2F series), the velocity profile near BDC is inherently different from a direct-drive crank. The link mechanism naturally slows down near BDC, so your programmed dwell might be effectively longer than you think. We measured actual slide velocity with a laser displacement sensor and found the real dwell was 180ms when we programmed 100ms. Not a problem per se, but it explains why some shops get different springback results with the same nominal profile on different press types.