Needle Detection

A conveyor-mounted needle detector uses balanced-coil magnetic-induction technology. Two receive coils sit either side of a transmit coil; a garment passes through the tunnel between them. Any metallic fragment disturbs the field balance, generating a signal proportional to fragment size and metal type. The detector stops the belt, sounds an alarm and diverts the piece to a reject bin.

The detector catches the fragment. The needle-log prevents the fragment from ever reaching the detector. Every serious sportswear factory runs a needle-control procedure with these rules:

• Every needle is stored in a central needle store, issued in exchange for the broken or worn needle it replaces.
• Operators sign a needle-issue register that names the machine, shift and needle count.
• When a needle breaks mid-shift, all fragments must be recovered and taped to the register entry.
• If any fragment cannot be recovered, work-in-progress from that machine is quarantined and re-detected before release.
• A missing fragment that cannot be re-located forces the WIP to be re-cut — expensive, but non-negotiable.

• Prefer plastic drawcord tips over metal aglets — one less trigger source.
• Nylon coil zippers detect cleaner than metal-tooth zippers.
• Woven labels over metal-crimped rivet labels for care information.
• Avoid metal-eyelet ventilation holes on youth sportswear; use bar-tacked buttonholes instead.
• Metal trims that must stay in the garment (branded rivets, snap fasteners) are pre-calibrated on the detector to be ignored.

• Detector calibration log — twice-daily test card entries with signatures.
• Needle-issue register — a full audit trail from store to operator to broken-needle disposal.
• Reject bin — physical pieces flagged during the last week, with reject reasons.
• Training records — every sewing operator inducted on the needle SOP with a signed acknowledgement.
• Machine map — every sewing machine numbered and tied to a maintenance schedule.