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Getting the feed timing right on a servo press progressive die line is more complex than on a mechanical press, but the servo gives you tools to optimize it that mechanical presses cannot match.
## Why Feed Timing Matters More on Servo Presses
On a mechanical press, the feed timing is fixed by the cam position. On a servo press, you can adjust the feed window anywhere in the stroke cycle. This flexibility is powerful but requires understanding the tradeoffs.
## The Feed Window
The feed window is the portion of the stroke cycle when the material can advance. It starts when the upper die clears the material on the upstroke and ends when the upper die contacts the material on the downstroke.
On a servo press, you can:
- Start the feed earlier in the upstroke (increases feed window, allows higher SPM)
- Use a faster return speed to create a longer feed window at the same SPM
- Program a dwell at TDC to give the feeder more time
## Calculating the Required Feed Window
Feed window required = (feed length / feed speed) + feeder acceleration time + safety margin
Example: 400mm feed pitch, 1200mm/s feed speed, 0.1s acceleration time
Feed time = 400/1200 = 0.33s
Total required = 0.33 + 0.1 + 0.05 (safety) = 0.48s
At 30 SPM, total cycle time = 2.0s. Feed window of 0.48s is 24% of the cycle - achievable.
At 50 SPM, total cycle time = 1.2s. Feed window of 0.48s is 40% of the cycle - tight, need to optimize.
## Optimization Strategies
1. Increase return speed: going from 400mm/s to 800mm/s return speed can increase the feed window by 30-40%
2. Reduce feed pitch: if the die design allows, shorter pitch means shorter feed time
3. Use a servo feeder: servo feeders can accelerate faster than pneumatic feeders, reducing the required feed window
4. Optimize the motion profile: use asymmetric profiles with fast return and slow approach
## Synchronization Setup
The press controller outputs a cam signal to the feeder. Set the cam on-angle to start the feed when the slide is 20-30mm above the material on the upstroke. Set the cam off-angle to stop the feed when the slide is 20-30mm above the material on the downstroke. Add 10-15 degrees of safety margin on each side.