Metal detector Troubleshooting: Causes & Fixes

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Problems on this page:

False rejects Missed contamination or low sensitivity Reject mechanism fault

False rejects

Hits OEE: Performance

Symptoms: Good product rejected, high reject rate, yield loss.

Product effect not compensated

Set up product learn/phasing; use the correct memory.

Electrical noise or vibration

Improve grounding, shielding and mounting; reduce vibration.

Wet/foil product handling

Use the right frequency/mode for the product.

Prevention: Proper product setup, EMC/mounting, correct mode.

Missed contamination or low sensitivity

Hits OEE: Quality

Symptoms: Failed test-piece checks, contamination passes, safety risk.

Sensitivity set too low or wrong setup

Set sensitivity to the smallest reliable sphere; re-learn product.

Aperture too large for the pack

Match aperture to product size; centre the product.

Drift or head fault

Run routine test-piece checks; service the head.

Prevention: Correct sensitivity, right aperture, routine validation.

Reject mechanism fault

Hits OEE: Availability

Symptoms: Reject does not fire or misses, contaminated product passes, stops.

Air supply or actuator fault

Check air pressure and the reject actuator/valve.

Timing or sensor issue

Set reject timing; check the product-tracking sensor.

Bin-full or confirm-sensor fault

Empty the reject bin; check confirmation sensors.

Prevention: Air/actuator maintenance, reject-timing checks, fail-safe interlocks.

Metal detector troubleshooting FAQ

Metal detector: what causes false rejects, and how do I fix it?

Symptoms: Good product rejected, high reject rate, yield loss. Likely causes: Product effect not compensated; Electrical noise or vibration; Wet/foil product handling. Fixes: Set up product learn/phasing; use the correct memory. Improve grounding, shielding and mounting; reduce vibration. Use the right frequency/mode for the product. Prevention: Proper product setup, EMC/mounting, correct mode.

Metal detector: what causes missed contamination or low sensitivity, and how do I fix it?

Symptoms: Failed test-piece checks, contamination passes, safety risk. Likely causes: Sensitivity set too low or wrong setup; Aperture too large for the pack; Drift or head fault. Fixes: Set sensitivity to the smallest reliable sphere; re-learn product. Match aperture to product size; centre the product. Run routine test-piece checks; service the head. Prevention: Correct sensitivity, right aperture, routine validation.

Metal detector: what causes reject mechanism fault, and how do I fix it?

Symptoms: Reject does not fire or misses, contaminated product passes, stops. Likely causes: Air supply or actuator fault; Timing or sensor issue; Bin-full or confirm-sensor fault. Fixes: Check air pressure and the reject actuator/valve. Set reject timing; check the product-tracking sensor. Empty the reject bin; check confirmation sensors. Prevention: Air/actuator maintenance, reject-timing checks, fail-safe interlocks.

Guidance only. Always follow lockout/tagout and your site's safe-work procedures, and verify against OEM manuals before acting.

Stop the same fault coming back

Recurring metal detector stops usually trace to a cause you cannot see by hand. The partner we recommend is Fabrico: EU-built, so your production data stays in EU jurisdiction, with computer-vision true-cause of micro-stops, a closed loop from PLC-read OEE to an auto-routed work order, and ISO 27001 / 20000-1 / 9001 (supports audit-readiness).

See how Fabrico finds root cause

OEE Lab is built and operated by Fabrico. The directory stays free.

Methods that cut recurring stops: the six big losses · root cause analysis · preventive vs predictive maintenance · TPM · SMED & changeover