Packaging Metal Detector Suppliers & Manufacturers

A packaging metal detector uses a balanced coil system to detect the presence of metallic objects in or on packages passing through its aperture. The detector consists of two receiver coils and one transmitter coil wound around an aperture; when no metal is present, the receiver coils are in electrical balance; a metallic object passing through disturbs this balance, triggering a signal that activates the rejection system. Metal detectors detect: ferrous metals (steel, iron) — the easiest to detect; non-ferrous metals (aluminium, copper, brass) — slightly harder to detect; stainless steel — the most difficult to detect, requiring advanced balancing technology, particularly in food applications where stainless steel is commonly present in processing equipment and packaging (foil lids, foil-laminate pouches). For stainless steel detection in food, the minimum detectable sphere diameter is typically 1.5–3.5mm depending on aperture size, product effect, and whether conductive or wet products are present. Food safety standards: BRCGS (BRC Global Standard for Food Safety), SQF, FSSC 22000, IFS Food, and other GFSI-recognised food safety schemes require food manufacturers to have validated metal detection procedures as part of their food safety plan. HACCP critical control points for metal contamination typically include a metal detector or x-ray inspection system at or after primary packaging. BRCGS requires a documented test protocol (standard test piece size and material, test frequency, rejection verification) and maintenance records.

The main technical challenge in food metal detection is the product effect — some food products (fresh meat, cheese, ready meals, wet produce, bread) are electrically conductive or have magnetic properties that create a signal similar to metal contamination, causing false rejects. Modern metal detectors manage product effect using: phase discrimination — electronics separate the product signal from the metal signal by phase angle; multi-frequency scanning — the detector runs at multiple frequencies simultaneously to optimise detection across metal types; automatic product compensation — the detector automatically learns and compensates for the product signal. Products with significant product effect require a metal detector specifically configured for the product type. For heavily product-effect-affected products (fresh bread with salt, fresh meat), testing the detector with the actual product before purchase is essential. Aperture size: the metal detector aperture (opening through which the conveyor passes) must be matched to the pack dimensions with minimum clearance. A larger aperture reduces detection sensitivity — specify the smallest aperture that fits the largest product format on the line. Pipeline metal detectors are installed in product pipework for detection in liquid, paste, or pump-transferred food products before packaging. Combined metal detector-checkweigher units combine both functions in a single machine, reducing line length and capital cost. When sourcing, specify: product type and whether product effect is expected, maximum pack dimensions, required detection standards (ferrous, non-ferrous, stainless sphere sizes), required food safety standard compliance, line speed, rejection method, and connectivity.