Belt material and false rejects
Many plants focus on detector head sensitivity while overlooking the conveyor belt that carries the product. Belts containing metal wire reinforcement, metal fasteners or conductive fillers enter the detection zone with every revolution, producing periodic signals that show up as regular false rejects or force operators to lower sensitivity. Ask the belt supplier for material details, confirm there is no metal carcass or metal splice, and select thickness and tensile strength according to product weight and belt width.
Splice type and signal drift
Splice design is an easily missed detail. Finger splices or vulcanized joints run flatter through the head and cause less signal fluctuation, while metal clips or rivets trigger a signal on every pass, so thresholds must be raised and real detection capability drops. Belt misalignment, frayed edges and buildup of oil or crumbs also change the belt's relationship with the coils, so belt inspection belongs in the daily checklist.
Cleaning, tension and re-verification
For maintenance, clean the belt surface and rollers regularly, adjust tension as specified, and avoid cleaning agents containing metal particles. After replacing a belt, re-verify sensitivity with test pieces and record the result before resuming production. Treating the belt as part of the detection system is often more effective than chasing detector specifications alone.