Routine Maintenance and Sensitivity Calibration of Needle Detectors

Routine maintenance of a needle detector starts with cleaning and inspection. After each shift, remove lint, metal filings and dust from the conveyor surface and around the detection head, since attached debris can affect detection stability. Check belt tracking and tension, and confirm that the photoelectric sensor, alarm and reject mechanism work properly. A daily checklist recording temperature, humidity, supply voltage and running status helps identify problems early and reduces false alarms or missed detection caused by dust, loose parts or moisture.

Sensitivity calibration should follow a fixed procedure using standard test pieces. Typically, iron and non-ferrous test pieces of the specified size are passed several times at different positions and orientations on the belt to confirm that the unit reliably detects them and triggers the alarm or reject action. Keep belt speed and pass height consistent with normal production, and avoid placing test pieces close to metal parts of the frame. Record calibration results, test-piece size and positions for traceability and trend comparison.

Higher sensitivity is not always better; it should be set according to product characteristics and customer acceptance criteria. Excessive sensitivity can be disturbed by product moisture or foil packaging, causing frequent false alarms, while insufficient sensitivity may miss small metal contaminants. Verify periodically with test pieces, and recheck after changing products, adjusting belt speed or moving the equipment. Combining routine maintenance with standardized calibration helps keep the detector stable over time and supports reliable outgoing quality inspection.