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 Automotive Bracket Stamping: Springback Control

admin

Springback is the primary quality challenge in automotive bracket stamping, especially with HSS and UHSS materials. Servo press motion control offers several techniques to minimize springback without secondary operations.

## Why Springback Occurs

When metal is bent or formed, the elastic portion of the strain recovers when forming force is removed. For DP590 steel, springback angle is typically 2-5?. For DP980, it can reach 8-12?.

## Servo Press Techniques for Springback Control

### 1. Dwell at BDC (Most Effective)

Hold the slide at BDC for 50-200ms after forming. This allows stress relaxation in the material, reducing springback by 30-60%.

Parameter setting: BDC dwell time in motion profile
- DP590: 50-100ms dwell
- DP780: 100-150ms dwell
- DP980: 150-200ms dwell

### 2. Overbend Compensation

Program the slide to go 0.5-2mm below nominal BDC, then return. The material springs back to the target angle.

Requires iterative tuning: start with 0.5mm overbend, measure springback, adjust.

### 3. Pressure Dwell (for Coining Operations)

For coining operations, increase forming pressure at BDC by reducing slide speed to near-zero in the last 1-2mm. This increases contact stress and reduces springback.

## Motion Profile Example for DP780 Bracket

```
TDC (0mm) —50mm above material: 300mm/s
50mm —5mm above material: 150mm/s
5mm above —BDC: 80mm/s
BDC dwell: 120ms
BDC —50mm above: 200mm/s
50mm above —TDC: 400mm/s
```

## Measuring Springback

Use a CMM or optical comparator to measure the formed angle immediately after forming and 24 hours later (some materials continue to relax). The difference is the springback angle to compensate for.

yuki_rnd

Springback compensation for automotive brackets in UHSS is an active research area. Our latest simulation work shows that combining servo press dwell with variable blank holder force during the stroke can reduce springback by up to 45% compared to constant-speed forming. The key is reducing blank holder force during the last 20% of the stroke to allow controlled material flow.

dave_toolmaker

For HSS brackets, over-bending is the traditional springback compensation method but it requires die modification. The servo press alternative: use a dwell at BDC to allow stress relaxation. Our data shows 80-120ms dwell reduces springback by 25-40% on 780 MPa steel without any die changes. Much cheaper than re-cutting the die.