What causes fault code CONV-METAL1 (Conveyor Metal Detector — Contamination Reject)?

Actual metal contamination in the product — foreign material from upstream process. Metal detector sensitivity too high — detecting product effect (metallic minerals in product). Conveyor belt splice has metal staples — detector picks up the splice on every rotation. Metal detector coils out of balance — environmental vibration or temperature change. Rejected product fell back onto the conveyor — reject mechanism not clearing product fully

How do I fix fault code CONV-METAL1?

Inspect the rejected product — open and search for metal contamination. Run test samples (ferrous, non-ferrous, stainless steel) through the detector to verify calibration. If false rejects on empty belt, check belt for metal splices or embedded metal debris. Re-balance the metal detector using the auto-learn function — run 20 good products through. Check reject mechanism — verify air pressure, solenoid, and reject confirm sensor. Verify environmental factors — vibration from nearby equipment can cause false triggers, isolate the detector on rubber mounts

Conveyor Metal Detector — Contamination Reject

CONV-METAL1

In-line metal detector on conveyor detected metal contamination in a product. Product has been rejected to the reject bin. Line may be stopped pending inspection.

medium conveyor packaging

conveyor metal detector contamination reject food safety quality

Probable Causes (ranked)

Actual metal contamination in the product — foreign material from upstream process
Metal detector sensitivity too high — detecting product effect (metallic minerals in product)
Conveyor belt splice has metal staples — detector picks up the splice on every rotation
Metal detector coils out of balance — environmental vibration or temperature change
Rejected product fell back onto the conveyor — reject mechanism not clearing product fully

Fix Steps

1 Inspect the rejected product — open and search for metal contamination
2 Run test samples (ferrous, non-ferrous, stainless steel) through the detector to verify calibration
3 If false rejects on empty belt, check belt for metal splices or embedded metal debris
4 Re-balance the metal detector using the auto-learn function — run 20 good products through
5 Check reject mechanism — verify air pressure, solenoid, and reject confirm sensor
6 Verify environmental factors — vibration from nearby equipment can cause false triggers, isolate the detector on rubber mounts

Field Trick

If your metal detector keeps false-rejecting on the belt splice, mark the belt splice location with paint and set up a splice suppression zone in the detector controller. Most modern detectors can learn the belt splice signature and ignore it. One programming change eliminates 90% of false rejects.

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