Height gaps shift product pose
Many factories focus on the detector head itself and overlook the conveyor transition just before the inspection zone. When a metal detector and the adjacent conveyors sit at different heights, products climb, drop or bounce slightly at the joint, and their orientation changes. As the product's position relative to the coil shifts, the signal baseline becomes unstable, the clear threshold is eaten by noise, and alarms for small metal pieces become intermittent.
Transition gaps add vibration
Transition gaps matter too. If a visible gap exists between two belts, small products may tilt or stall, or be scraped by the belt edge and generate metal debris. With a large gap, the product's centre of gravity shifts inside the inspection zone and belt tension becomes uneven, adding mechanical vibration. These factors do not disable the machine at once, but they steadily reduce detection consistency, so the same product sometimes triggers an alarm and sometimes passes.
Include joints in acceptance
During purchasing and installation, include the transition section in acceptance checks: verify the height, belt surface flatness and gap dimensions between the detector inlet/outlet and adjacent line sections, and require smooth transitions with controlled gaps. During trials, run actual products at normal speed and watch for bouncing or tilting. Routine checks should also cover cleaning and fastening of the transition area so small issues do not accumulate into missed detections.