Conveyor Metal Detector for Wet Food | SameGram DD-390

This article explains how the DD-390 deals with the problems plant managers hit every shift, and how to commission it for your product rather than a laboratory.

In any HACCP plan, a metal detector sits at a Critical Control Point — the last dependable barrier before product ships. It protects downstream equipment from rogue metal and your brand when one contaminated pack could mean a recall. For plants running multiple categories, the same unit often has to cover very different products in a single day. See how we apply this across sectors in our industry applications overview.

The harder your product is to inspect, the more your detector's design matters — and wet, salty food is about as difficult as it gets.

The DD-390 runs dual-frequency detection tuned to the product in front of it. During setup it performs a full product calibration: it learns the uncontaminated product's signal, measures both resistive and reactive components, and sets a phase angle that separates product from metal. The measured ratio stays constant for clean product and breaks the moment metal is present — that is the trigger.

What makes this practical is the self-learning and memory function. Once a product is taught, its parameters are stored. The DD-390 holds more than 200 recipes, so a line that switches between frozen fish, bread, and sauce packs can recall each one without re-tuning. Auto calibration is straightforward: run at normal speed, keep at least one head width of spacing between packs, and pass 30 to 50 clean units through the head. Our metal detection solutions page covers the full model range.

That capability — learn once, recall instantly — is what keeps a wet-food line running instead of stalling at every changeover.

False rejects are the silent tax on a food line — lost margin and a sign your settings are drifting. The DD-390 attacks this two ways.

First, the 200-recipe library means changeover is a menu selection, not a re-engineering job. Second, reject timing is tunable so the machine removes only the contaminated unit. Package spacing is set as a percentage of pack length — usually 100 percent — and if you are unsure which unit is contaminated, you can fine-tune whether it rejects one pack or two. After any timing change, verify by taping a test piece to a product, running it through, and confirming the reject fires to remove only that pack. On combined lines, our combination inspection systems fold weighing and metal checking into one logic.

The honest takeaway: no detector eliminates every false reject, but a unit that learns your product and stores the result stops most of them at the source.

The DD-390 stores up to 1,500 event logs with a running reject total, per-product reject history, and production counters. Combined with the daily verification test, you get a traceability trail that satisfies an auditor without a separate spreadsheet. Our quality and compliance resources explain how to document this for retailer audits.

For HACCP validation: commission each new product with full calibration, test certified pieces at the leading edge, center, and trailing edge (and on top, inside, and underneath), repeat at least three times per metal type, and record date, time, product, piece size, and pass or fail. If a piece fails after adjustment, the guidance is explicit — do not run production, and contact technical support.

Integration is where many detectors fail quietly. The DD-390 ships with six configurable relay outputs — Reject 1, Reject 2, Fault, Alarm, Warning, and QA Light — and a photoelectric input that synchronizes inspection with rejection. That lets it drive a pneumatic pusher, air blast, or flap gate and signal your line controller or stack light without custom electronics. Modular construction means the belt, reject device, and search head are serviceable without a full teardown.

If your line already runs our checkweighers or combination systems, the metal detector slots into the same control logic, keeping training and maintenance simple.

● Detection sensitivity (empty belt): Fe 0.8 mm / Non-Fe 1.2 mm / SUS316 1.5 mm

These figures are the practical, product-detection values relevant to production — not laboratory maxima — and they should be confirmed against your own product during commissioning.

Can a metal detector find glass, stone, or bone? No — the DD-390 detects metal only. For non-metallic objects, pair it with an X-ray system from our broader inspection range.

Why does frozen food temperature change sensitivity? Partially thawed product releases free water, raising the product effect. Keep stock at a stable temperature and re-run auto calibration if conditions shift.

Do I need to recalibrate every product? Only when you first introduce it, or after a significant formulation, temperature, or line change — after that it is a one-tap recipe recall.

Author: Tony, Founder & CTO, SameGram.