Picanol GTM Error Code 121

Picanol Textile Major Weaving

Model: GTM | Code: 121

Applicable Systems
GTM

Symptoms

The Picanol GTM weaving machine displays fault code 121: WRONG ROTATION. The machine logic has detected that during slow-speed rotation, the loom completed one revolution but the rotation deviated more than 4 degrees in the reverse direction from the expected position. This indicates a timing or encoder error in the main shaft position feedback system.

Possible Causes

  • Main shaft encoder (shaft angle encoder) registering incorrect positions due to encoder disc damage or contamination
  • Encoder coupling loose or damaged, causing the encoder to slip relative to the main shaft and report wrong angular positions
  • DPSK drive board fault causing incorrect interpretation of the encoder signal and erroneous position calculation
  • Mechanical misalignment between the encoder mounting and the main shaft causing cumulative position error over one revolution
  • Encoder cable fault: intermittent connection or signal interference causing the controller to read erroneous position data

Troubleshooting Steps

  1. Step 1: Manually rotate the reed (beater) through one complete revolution by hand and check the angle position display on the operator panel
    The displayed angle should change smoothly through 360 degrees and return to the starting position with less than 1 degree of error
  2. Step 2: Inspect the shaft encoder coupling for looseness, cracking, or damage that could cause encoder slip
    Coupling should be tight with no play between the encoder shaft and the main shaft; replace if any movement is detected
  3. Step 3: Check the encoder cable and connectors for damage, loose pins, or corrosion
    Cable should be intact with securely seated connectors; signal integrity can be verified with an oscilloscope if available
  4. Step 4: If the encoder is suspect, swap it with a known-good unit and re-test the slow-speed rotation
    If the fault clears with a replacement encoder, the original encoder is defective and should be replaced
  5. Step 5: If the encoder and cable are confirmed good, the DPSK drive board may be faulty and should be inspected or replaced
    Contact Picanol service for DPSK board diagnostics; the board processes encoder signals and a fault here causes position errors

How to Reset

To reset: 1) Identify and resolve the rotation error cause (encoder, coupling, cable, or DPSK board). 2) Clear the fault on the operator panel. 3) Run a slow-speed test cycle to verify correct rotation tracking. 4) If the fault does not recur, resume normal weaving operation. Caution: Running the loom with incorrect shaft position feedback can cause weft insertion timing errors and fabric defects.

Frequently Asked Questions

  • Q: What does the shaft encoder do on a Picanol GTM loom?

    The shaft encoder on the Picanol GTM monitors the angular position of the main shaft throughout each revolution. This position data synchronizes all loom functions including weft insertion, shedding, and beat-up. A faulty encoder causes timing errors that disrupt the weaving cycle and trigger fault code 121.

  • Q: Can I continue running the loom if code 121 appears intermittently?

    No. Fault code 121 indicates a serious position feedback error. Intermittent occurrence typically indicates a degrading encoder coupling or cable connection that will eventually fail completely. Continued operation risks fabric defects and potential mechanical damage from mistimed shedding and beat-up. Diagnose and repair the fault before resuming production.

Related Picanol Fault Codes

Source: Picanol GTM Machine Messages and Fault Codes Manual

Category: Textile