Material Misalignment / Skewing
NC servo feeder misalignment is lateral movement: the strip walks left or right, rubs a guide, loses centerline or enters the die at an angle. The steering force can come from the coil, guides, rolls, upstream loop, feeder mounting or die entrance.
NC Servo Feeder Misalignment (Material Skewing)
Misalignment is not the same as a short feed. A strip can advance the correct pitch and still walk sideways. Record lateral position at several reference points—upstream of the feeder, at the roll entry, at the feeder exit and at the die entrance—to identify where the direction first changes.
| Pattern | Useful evidence | First branch |
|---|---|---|
| Drifts steadily to one side | Centerline marks and left/right guide contact | Coil shape, guide geometry, roll contact and parallelism |
| Changes direction during the coil | Coil position, loop shape, camber and tension | Raw material and upstream line |
| Starts only at the die entrance | Feeder exit centerline versus die entry | Mounting, pass line, die guide and pilot stage |
| Appears with short feed and visible roll marks | Pitch series and slip evidence | Feed slipping |
Punch Feeder Misalignment: Coil, Guide and Material Checks
Before changing the feeder, inspect the strip itself. Camber, coil set, uneven thickness, heavy edge burr, damaged edges or telescoped winding can create a steering force. Compare the direction of strip curvature with the observed drift and record whether the symptom repeats with another approved coil.
- Camber: the strip edge curves along its length and pushes against one guide.
- Coil set or crossbow: the strip does not lie predictably through the entry and rolls.
- Burr or edge damage: one edge drags or catches at a guide or die entrance.
- Width/thickness variation: contact and guide clearance change as the coil runs.
- Surface contamination: oil or debris can change left/right roll friction.
- Winding condition: a telescoped or damaged coil changes upstream alignment.
Inspect Guide Contact Without Using a Universal Gap
Entry and exit guides should control the material without forcing a new centerline or pinching the strip. There is no universal 5 mm clearance. Use the machine and job setup document for guide type, strip width, thermal or surface allowance and the required measurement method.
- Mark the intended material centerline from the released setup.
- Record where each guide contacts, including polished or damaged edges.
- Check that a guide is not bent, loose, contaminated or acting as a steering point.
- Confirm that the guide centerline agrees with the feeder rolls and die entrance.
- Make only the permitted guide adjustment and measure the next series.
Compare Left and Right Roller Contact
Uneven contact can steer a strip, but the cause is not always spring adjustment. Check the installed clamping mechanism, roll cleanliness, local wear, strip thickness, roll parallelism, bearing condition and release motion. Use pressure paper, contact marks or the method specified for the feeder if available.
Check Roller Parallelism and Mechanical Condition
Qualified maintenance should verify upper/lower roll parallelism, shaft and bearing condition, mounting security, release travel and local wear using the supplied tolerances. A roll that is angled, grooved or contaminated can steer the strip even when guides and springs appear symmetrical.
Check the Upstream Loop and Pull Direction
A loop that is off center, touching a frame or changing tension can pull the strip sideways before it reaches the feeder. Record loop position during decoiler and straightener movement. The correction may belong to upstream alignment or loop control rather than the feeder head.
| Observation | Investigation branch | Escalation point |
|---|---|---|
| Strip already off center before the feeder | Decoiler, straightener, loop and upstream guides | Unstable or uncontrolled coil/loop motion |
| Centerline changes inside the feeder | Guides, roll contact, parallelism and release | Internal wear, binding or access behind guards |
| Centerline changes only at the die | Feeder mounting, pass line, die entry and pilots | Tooling correction or collision risk |
| Direction changes with speed | Acceleration, loop dynamics and released capability | Parameter or drive work without approved procedure |
Verify Feeder-to-Die Centerline and Pass Line
Confirm the feeder mounting, pass-line height, exit support and material centerline against the released installation and die setup. A guide should not be used to bend the strip into a misaligned die entrance. If the symptom begins after a die change, use the dedicated changeover checklist.
After Die ChangeCheck changed die, material, pitch and release conditions.
Installation GuideMounting, centerline, signals and acceptance.
Do Not Confuse Misalignment With Feed Slipping
Misalignment is lateral; slipping is relative motion between the rolls and strip. They can occur together, but each requires separate evidence. If the strip walks sideways because one side is slipping, document both the lateral position and the actual pitch before correction.
Verify the Correction
- Restore the approved baseline and all guards.
- Mark centerline references at the feeder entry, exit and die entrance.
- Run a defined number of low-speed feeds with the actual material.
- Record lateral movement and pitch at each reference point.
- Increase speed only through the approved commissioning sequence.
- Inspect strip edges and part quality before production release.
Frequently Asked Questions
Why does strip material move to one side in an NC servo feeder?
Possible branches include material camber or burr, guide contact, uneven roll contact, roll parallelism, upstream pull and feeder-to-die misalignment. Measure where the centerline first changes.
Should I tighten the spring on the side where the strip drifts?
Not as a universal rule. That can hide material, guide or alignment problems and can damage the strip. Use the installed feeder’s contact-check and adjustment procedure.
What guide gap should be used?
There is no universal value. Use the machine and job setup for guide design, material width, surface condition and required clearance.
Can a poor coil cause feeder misalignment?
Yes. Camber, coil set, thickness variation, edge burr or telescoped winding can create lateral force before the strip reaches the feeder.
Can material slipping cause skewing?
Yes. Unequal left/right grip can produce both short feed and lateral walking. Record pitch and centerline separately.
Related Feed-Error Pages
Feed SlippingUse when the rolls move but the strip advances less or retreats.
Auto Mode StopsUse when manual motion works but the sequence does not continue.
Send a Misalignment Evidence Package
Include the feeder, material and die identity; centerline photos; drift direction; consecutive pitch data; coil and loop video; guide contact; recent changes and checks completed.
