Packaging & Inspection
Vertical Form Fill Seal Machine
Snack, nut, frozen food, grain and powder producers moving from manual bagging to automatic packing.
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09 · Packaging & Inspection — Equipment
Food Metal Detector
An inline metal detector that checks packed or loose food for metal contamination and automatically rejects affected product.
- Rating
- Matched to line speed (m/min or pieces/min); sensitivity depends on product and aperture
- Versions
- Conveyor · Gravity-fall · Pipeline
- Best for
- Food plants that must screen products for metal before shipping or before critical machines
- Detects ferrous, non-ferrous and stainless metals within agreed test sizes
- Set up and checked with your real product and packaging
- Reject systems: air blast, pusher, flap or diverter valve
- Reject confirmation and event logging options
Short answer: A food metal detector senses metal fragments in products as they pass through an electromagnetic field, and a reject device removes the contaminated item from the line. The configuration is decided by how the product moves (packs on a belt, falling bulk or pumped through a pipe), by the product effect of wet or salty food, and by the packaging material.
How it works
The search head contains coils that create a balanced electromagnetic field. When a conductive or magnetic particle passes through, it disturbs that balance, and the electronics compare the signal with the learned signal of good product. If the disturbance exceeds the threshold, the controller times the reject: an air blast, pusher or retracting belt for packs, a flap for falling product, or a diverter valve for pipelines.
Wet, salty, warm or frozen foods produce their own signal, called product effect. The detector learns this signal so that it does not reject good product, which is why setup should be done with real product and packaging.
Which configuration fits
| Form | Suits | Watch out for |
|---|---|---|
| Conveyor | Packs, trays, loose pieces | Metallised film limits sensitivity |
| Gravity-fall | Powders, grains, snacks before bagging | Needs steady, free-flowing product |
| Pipeline | Sauces, liquids, meat masses | Pipe size and pump pressure must match |
The smaller the aperture relative to the product, the better the sensitivity, so the head is chosen as close to the pack size as handling allows.
What we need from you to quote
- Product, temperature and whether it is wet, salty or frozen
- Packaging material and pack dimensions, or pipe or chute diameter
- Line speed and product spacing
- Test piece sizes and metal types you need to validate
- Reject method, confirmation and logging requirements
- Cleaning method and room conditions
- Power and compressed air supply
Where it sits in a line
Metal detectors are usually placed after packing, for example after a VFFS packaging machine or tray sealer, often combined with an in-line checkweigher. Gravity units can protect equipment such as a spice grinding machine. For foil packs or bone and glass risks, a food X-ray inspection system is the alternative.
Common configurations
- Option A
Conveyor
packs or loose products pass on a belt through the detector head; the most common type for finished packs.
- Option B
Gravity-fall
free-flowing powders, grains or snacks fall through a vertical tube, often just above a bagger.
- Option C
Pipeline
pumped liquids, sauces and meat masses flow through a pipe in the detector, with a reject valve.
What we confirm before quoting
Our engineers check these points with you, so the quotation fits your site rather than a catalogue default.
- 01Product effect: how wet, salty or warm the product is
- 02Packaging material, especially metallised film or foil
- 03Aperture size relative to the pack or flow
- 04Test pieces and sensitivity targets to validate against
- 05Reject device and how rejection is confirmed and recorded
Frequently asked questions
What size of metal can it detect?
Sensitivity depends on product effect (wet, salty or warm food behaves partly like metal), the aperture size, metal type and position in the pack. There is no single figure; we agree test pieces with you and set up the detector on your actual product.
Can it inspect products in foil packaging?
Standard metal detectors struggle with aluminium foil or heavily metallised film. In that case, inspect before packing, or consider a food X-ray inspection system, which looks for density differences rather than conductivity.
How should the detector be tested in daily production?
Most plants pass certified test pieces through the detector at set intervals and record the result, checking that each piece is detected and actually rejected. We can include a reject confirmation sensor and a locked reject bin to support this routine.
Get a quote for the Food Metal Detector
Tell us your raw material, finished product and target output. Our engineers reply with a matched configuration and quotation.
What to send with your inquiry
- 1Raw material and its condition
- 2Finished product and packaging
- 3Target output — raw input or finished product
- 4Site photos, power supply, utilities
Email sales@hnfoda.com
Buyer guides
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