What is a servo press?

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

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

Progressive die feed timing on servo - sync issues

nick_metals

Having feed timing sync issues on our progressive die setup. The servo press timing is different from our old mechanical and I'm struggling with the adjustment.

**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.

toolndye_dave

Feed timing on servo presses is actually easier than mechanical once you understand the concept. On a mechanical press, the feed window is fixed by the cam timing. On a servo, you define the feed window in the motion profile —you can make it as long as you need. I've set up progressive dies that were impossible to run on mechanical presses because the feed window was too short.

anna_plc

The key parameter is the feed signal output angle. On most servo press controllers, you set the crank angle at which the feed signal activates. Start conservative (feed signal at 180? —top of stroke) and narrow it down. If you get misfeed alarms, the window is too tight. We typically run 160?-200? for the feed window.

pressroom_tom

Feed timing on progressive dies is the one thing that trips up every shop switching from mechanical to servo. The mental model is different: on a mechanical press you work around a fixed cam window, on a servo you design the window.

What I do on every new die setup: start with the feed signal at 180 degrees (TDC) and a wide window, then tighten it 5 degrees at a time while watching the pilot pin entry. When the pilots start showing witness marks on one side, you have gone too far. Back off 5 degrees and that is your production setting.

One thing nobody mentions: the feed signal delay matters as much as the angle. Most servo feeders have a 15-30ms response lag from signal to actual strip movement. At 60 SPM that is about 3 degrees of crank rotation, no big deal. At 200 SPM it is 10+ degrees and you have to compensate by advancing the signal. I keep a cheat sheet taped to each die with the actual measured delay for that specific feeder-die combo.

Also check your pilot pin length vs feed height. If the pilots are short and the feed lifters are set high, the strip can shift during the free flight between lifter release and pilot engagement. That shows up as intermittent misfeed alarms that drive you crazy because they are not repeatable.

mchen_servo

The pilot pin witness mark method pressroom_tom described is exactly right ? that's the gold standard for dialing in feed timing on progressive dies.

What I'd add is the acceleration profile matters as much as the feed window angle. On a mechanical press the feed accelerates and decelerates on a fixed cam profile. On a servo, the feeder controller usually lets you set accel/decel ramps independently. If you're getting inconsistent feed lengths (say ?0.1mm variation), it's almost always the decel ramp being too aggressive ? the strip overshoots the target position and the feeder brake can't catch it in time.

We run Komatsu H2F presses with Sankyo feeders and the magic number for us is 70% of max feeder speed with a decel ramp of about 15 degrees before the feed window closes. That gives the strip enough time to settle before the pilots engage. Going faster than that and we start seeing pilot pin wear on one side ? exactly the witness mark symptom.

One more thing: if you're running thick stock (2mm+), add a pilot release delay. The strip needs a few milliseconds to relax after the pilots release before the feeder pulls. Without that delay, the strip is still slightly compressed from the pilots and your feed length comes up short by 0.02-0.05mm. Doesn't sound like much but over 15 stations it compounds.

Also check your loop sensor position if you're using a loop control feeder. I've seen shops where the loop sensor was set for their old mechanical press speed and the servo's variable speed confused the sensor ? it would call for more strip during the dwell portion of the stroke when the press was barely moving, creating a huge loop that then whipped during the fast portion.