The needle detection (metal detection) problem for garment trims is very concrete: the buyer wants the whole shipment to pass a detector, but the tags carry iron eyelets, metal fasteners or steel pins, the machine keeps alarming and the goods sit on the packing line. This is rarely a machine fault — it is usually a trims selection that was never aligned with the detection requirement at quotation stage.
This guide explains what a detector actually catches, how seven common trims behave on the two main machine types, what to do when a metal part must stay, how to select trims for orders that must pass detection, and what the detection label and records need to contain — plus an enquiry checklist.
1. What a Detector Catches and What It Misses
Detection exists to screen out broken needles, sewing needles, staples, blade fragments and metal fibres. There are two machine families with different physics, and they react differently to trims.
- Magnetic needle detectors: sensitive to ferrous metal (iron, carbon steel, some martensitic stainless); the most common machine on the line, with sensitivity rising as the aperture gets smaller
- Balanced-coil metal detectors: can catch non-magnetic metals such as copper, aluminium and brass, but are more sensitive to aperture and product effect, so poor settings cause false rejects
- The key point: it is never about containing metal, but about whether it is detectable on a given machine at a given sensitivity. Naming the machine and sensitivity on the confirmation sheet ends most arguments
2. Seven Common Trims Under the Detector
| Trim | Magnetic detector | Metal detector | What to do |
|---|---|---|---|
| Iron eyelet | Alarms | Alarms | Switch to brass or stainless, or keep the tag out of the detection flow |
| Brass or aluminium eyelet | Usually passes | May trigger | Note material and position so the buyer can set sensitivity |
| Metal fastener (spring wire) | Alarms easily | Alarms | Use plastic fasteners or paper clips and confirm before assembly |
| Steel safety pin | Alarms | Alarms | Put it on the remove-before-detection list, or switch to plastic or paper |
| Large foil-stamped tag | May alarm depending on sensitivity | Alarms at some settings | Run it separately, adjust sensitivity or reduce foil area |
| Metallic yarn woven label | May alarm | May alarm | For detectable orders switch to polyester yarns; a metallic look is still possible |
| Plastic fastener, cotton cord, heat transfer | No alarm | No alarm | First choice for detectable programmes — still verify pull strength |
3. When a Metal Part Has to Stay
Zipper pulls, metal buttons and decorative metal parts are functional and safety components — they cannot simply be removed. Four approaches are used in practice.
- Split-stage detection: detect the garment first, before tags and pins are fitted, then attach trims
- Isolation list: list known metal parts as permitted items, have the buyer sign them off, then spot-check positions instead of alarming on every piece
- Sensitivity grading: set the machine to just catch the target needle size, changing the test-piece spec if needed, so false rejects drop
- First-piece and batch-change checks: verify with test pieces at every start-up and batch change, and record it so alarms can be traced
4. Choosing Trims for Orders That Must Pass Detection
- Hang tags: paper with cotton or elastic cord and no iron eyelet; if reinforcement is essential, use brass or stainless and note it
- Woven and care labels: standard polyester and nylon yarns are metal-free; skip metallic yarns, foil yarns and some reflective yarns
- Packing: plastic fasteners, paper clips and metal-free self-seal bags; avoid staples, iron clips and wire ties
- Labelling and segregation: mark detectable and non-detectable packs inside and outside the carton so nothing is run wrongly or skipped
5. Detection Labels and Records
- The detection label usually carries date, machine number, sensitivity, operator and batch — fixed to the outer bag or carton in an agreed position
- Detection and broken-needle logs must be retained — they are always checked in factory audits
- Agree in advance who detects (garment factory or packing house), the label format (sticker or printed) and where it goes
6. Four Most Common Stoppages and Rework Causes
- Metal trims are not listed, so the batch alarms repeatedly and every piece has to be checked by hand
- An oversized foil area alarms at low sensitivity yet risks missed needles at high sensitivity
- Spare buttons pinned with a metal pin trip the detector on the whole pack
- Rework is not re-detected and logs are missing, so shipping documents fail spot checks
7. Enquiry Checklist
| Item | What to state |
|---|---|
| Detection required? | Whole shipment, split-stage, or garment body only |
| Machine and sensitivity | Magnetic needle detector or metal detector, target needle size and test piece |
| Metal parts list | Position, material, quantity, and whether they may stay |
| Acceptable alternatives | Are plastic fasteners, cotton cord, metal-free eyelets or polyester yarns acceptable? |
| Detection label ownership | Who supplies it, sticker or printed, and where it is applied |
| Records and traceability | Batch mapping, retention period, documents needed for audits |
Related Articles
- Trims FAQ: all articles
- Hang Tag Metal Hardware Guide: Eyelets, Fasteners and Pins
- Hang Tag Plastic Fastener Guide: Sizes, Load and Fitting
- Nickel Release Compliance for Metal Trims
- Clothing Label Compliance for Japan
Must this order pass detection? Send the machine type, sensitivity, target needle size and tag or packing requirements — we propose a detectable trims set at quotation stage and ship samples in 3–7 days.
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