Registration Mark Detection Problems

Problem

At low speed the print aligns correctly with the cut and seal. As speed increases, the cut position begins to wander, the HMI reports registration faults, or the machine auto-stops when the mark is not detected.

Possible Causes

1. Photocell response or gain is marginal for the higher passing frequency.
2. Mark contrast or print quality is borderline for reliable detection.
3. Film tension at speed stretches or oscillates the web.
4. Registration correction parameters are tuned for a lower speed range.
5. The sensor bracket vibrates or has shifted.

What to Check

• STEP 1Re-teach the photocell at production speed.Detection tuned at standstill may not be valid at speed; follow the teach-in procedure in the machine manual at operating speed.
• STEP 2Inspect the mark and the sensor optics.Confirm mark contrast and cleanliness of the sensor lens; check bracket fixation.
• STEP 3Observe tension behavior at speed.Watch for web oscillation between rollers that appears only near production speed.
• STEP 4Review registration parameters.Compare correction window and gain settings with the values recorded for this product.
• STEP 5Find the speed threshold.Determine the speed at which faults begin — a sharp threshold localizes the limit.

Corrective Actions

• Store per-speed registration settings in the recipe where the HMI supports it.
• Keep the sensor and its bracket on the daily cleaning and inspection checklist.
• If tension oscillation appears at speed, record the speed threshold and the film specification and involve Path Pack support.
• Track fault frequency per film batch — borderline print quality shows as batch-dependent faults.

Advanced Diagnostics: Sensor Substitution and Print Quality

When registration faults survive cleaning, alignment and speed-correct teaching, two deeper routes remain: the sensor channel and the printed mark itself.

• STEP 1Substitute a known-good sensor.Where an identical spare is stocked, swapping it isolates sensor vs wiring vs controller in one step — then re-teach at production speed.
• STEP 2Verify the detection timing chain.Confirm the registration input reaches the motion system with stable timing — intermittent offsets that survive substitution point here, not at the sensor.
• STEP 3Check the mark itself against the print specification.Mark contrast, size and placement are print parameters — agree them with the film supplier rather than compensating at the machine.