Feed Slipping / Material Retreat
Servo-feeder slipping is a specific symptom: commanded roller motion does not produce the same strip movement, or the strip moves backward after feeding or release. Separate that symptom from lateral skew, a missing automatic command and a wrong programmed pitch.
Is the Problem Really Feed Slipping?
| Observed result | Likely page owner | What to record first |
|---|---|---|
| Rolls turn but the strip advances less, or marks show relative movement | This slipping page | Commanded pitch, actual pitch, roll mark and material condition |
| Strip walks left or right while pitch may remain correct | Misalignment / skew | Direction, centerline, guide contact and coil condition |
| Manual motion works but Auto feeds once and stops | Auto-mode no-feed | Counter, program step, trigger and handshake state |
| Every measured pitch has a fixed offset without evidence of slip | Feed-error workflow | Target pitch, measurement method and consecutive results |
Capture a Repeatable Slipping Pattern
- Machine and job: feeder model, press, die, recipe, material, width, thickness, surface and target pitch.
- Actual movement: consecutive pitch measurements and whether the error is short, intermittent or followed by backward movement.
- Cycle stage: acceleration, steady feed, stopping, release, pilot correction or press restart.
- Contact evidence: roller marks, polished areas, oil, debris, scratches, local deformation and strip temperature.
- Upstream condition: loop shape, decoiler/straightener motion, tension change, whipping and unsupported strip weight.
- Recent change: new coil, lubricant, die, speed, pitch, release setting, maintenance or feeder relocation.
NC Servo Feeder Material Slippage: Grip and Pull-Back Checks
Grip is created by the installed roller surface, the approved clamping mechanism and the strip condition. Pull-back is the resistance that the feeder must overcome. A slipping diagnosis must examine both sides of that balance.
Material surface
Record lubricant, scale, coating, burr, contamination and local thickness changes. Do not clean or apply chemicals that are incompatible with the strip or roll material.
Roller surface
Inspect accessible roll areas for oil, embedded debris, wear, damage and uneven contact. Internal cleaning or resurfacing belongs to the machine procedure.
Clamping state
Confirm that the selected mechanical or pneumatic arrangement reaches its intended clamp state. Compare the actual configuration with the feeder drawing.
External resistance
Look for guide drag, strip buckle, die-entry resistance, excessive loop weight or upstream equipment pulling against the feeder.
Material Retreat After Release: Why the Strip Goes Back
Backward movement can occur when the strip is released while an external force is still acting on it. That force may come from an unsupported loop, upstream tension, strip spring-back, die contact, a guide or an incorrect release event. Record the exact moment the strip retreats.
- Confirm whether retreat begins before release, during release or after the rolls clamp again.
- Observe whether upstream equipment or loop motion changes at the same time.
- Confirm whether pilot correction or die contact is moving the strip while the feeder is open.
- Compare the release command and actual release motion under the approved setup procedure.
- Do not copy a cam angle, cylinder connection or spring from another machine.
Interface VerificationVerify the feederโpress sequence from released documents.
Signal CamPhysical cam and sensor installation context.
Check the Upstream Loop and Pull-Back Load
The feeder should receive material without uncontrolled tension. A heavy unsupported span, a loop touching surrounding equipment, a straightener that does not keep up, or a decoiler control problem can add resistance and create an intermittent short feed.
| Observation | Possible investigation branch | Do not assume |
|---|---|---|
| Slip coincides with loop becoming tight | Upstream speed, loop control, sensor and line layout | Do not increase roller pressure before resolving pulling |
| Slip appears only near the end or start of a coil | Coil condition, payoff resistance and loop geometry | Do not call it a servo accuracy fault from timing alone |
| Wide or thick strip oscillates | Support, acceleration and released line design | Do not add an improvised support in a moving hazard zone |
| No upstream correlation | Roll contact, release, die entry and feeder mechanics | Continue with measured evidence |
Confirm Material Is Within the Released Feeder Range
Check the supplied feeder specification for material width, thickness, strip condition, feed length, acceleration and release type. A job outside the released range is an application mismatch, not a pressure-adjustment problem. Do not compensate for excess load by unapproved spring, cylinder, motor or parameter changes.
Inspect Mechanical Condition Without Guessing the Failed Part
After external resistance and contact conditions are checked, qualified maintenance can evaluate roll parallelism, bearing condition, gear or belt transmission, backlash, release travel and mounting. Abnormal heat, noise, binding, damaged hardware or repeatable AL.50 events require controlled service rather than continued production.
Verify the Correction
- Restore guards and the approved baseline.
- Run the permitted manual or setup test and confirm release and clamp states.
- Measure a consecutive series at the defined pitch and speed.
- Check strip surface and part condition for new marks or deformation.
- Run low-speed automatic cycles and watch the loop, rolls and die entry.
- Record the changed variable, before/after measurements and acceptance decision.
Frequently Asked Questions
Should I increase roller pressure when a servo feeder slips?
Only after slip is proven and the installed feeder procedure identifies the approved pressure adjustment. Excess force can mark material, deform soft strip or overload components.
Why does material go back after feeding?
Record whether retreat occurs during release. Upstream tension, loop weight, strip spring-back, die correction, guide drag or an incorrect release event can move material while the rolls are open.
Do yellow and green springs have a universal meaning?
No. Spring color, rate and permitted compression belong to the supplied feeder configuration. Use the part list and manufacturer procedure for that machine.
Should a second air line be added for thick material?
Not from a generic instruction. Pneumatic ports and valve logic vary. Compare the installed cylinder and solenoid arrangement with the released pneumatic drawing.
Can upstream equipment cause a short feed?
Yes. If the loop becomes tight or the straightener/decoiler pulls against the feeder, roller grip can be lost even when the feeder head itself is functional.
Related Feed-Error Pages
Material MisalignmentUse when the strip walks left or right.
Auto Mode StopsUse when manual motion works but the next feed command is missing.
Send a Slipping Evidence Package
Include feeder model, material, target and actual pitch series, strip and roll photos, the cycle stage, loop video, recent changes and checks completed.
