Laser marking or label printing for traceability
Both are legitimate. The decision is made by your process, not by preference, and the expensive mistake is in the scanner budget rather than the marker.
Start with what the part goes through
Identity has to survive from the operation it is applied at to the last time anyone needs to read it — which, for a warranty claim, is years after dispatch and in someone else's workshop.
| Process step | Printed label | Laser DPM |
|---|---|---|
| Wash / degrease | Usually fails | Survives |
| Paint or powder coat | Fails, or must be re-applied after | Survives if applied post-coat, obscured if pre |
| Heat treatment | Fails | Survives on most substrates |
| Handling and stacking | Abrades, peels at edges | Survives |
| Field life, years outdoors | Adhesive fails | Survives |
| Cost per station | Low — one printer serves a line | High — marker plus DPM scanners |
The rule that decides it
If the part goes through wash, paint or heat after identity is applied, you need a direct part mark. If it does not, a printed label is the cheaper, faster and more flexible answer, and choosing a laser anyway is spending money on a problem you do not have.
Data Matrix, not QR, for direct marking
For DPM the code should be a Data Matrix. It is more robust at small sizes, has better error correction per unit area, and reads reliably at low contrast — which is exactly what a laser mark on bare metal is. QR is the right choice on a printed label where contrast is high and a phone camera may be the reader.
The scanner mistake
This is the one that sinks projects. An ordinary 1D or general-purpose 2D scanner will not reliably read a laser mark on bare metal. Reading a DPM code needs an imager with appropriate illumination: diffuse dome lighting for shiny or curved surfaces, low-angle for etched flat surfaces.
Budgeting an inexpensive scanner per station and discovering this at commissioning is the classic failure in these projects. If you are marking at operation 1, every station downstream that reads identity needs a DPM-capable imager — and that is a per-station cost, not a one-off.
Mark quality is measurable, so measure it
A mark that reads today on a new scanner and fails in two years on a customer's reader was never a good mark. Grade the mark on application and record the grade. When grades start drifting, the laser needs attention before you start losing readability in the field.
Read the mark back and verify it matches the intended identity before the unit is allowed to advance. A mark that was applied but never verified is a unit with an identity nobody has confirmed.
Mixed is normal
Plenty of plants run both: a direct mark on the raw part at the first operation so identity survives the process, and a printed label at dispatch carrying the customer's required format, barcode symbology and branding. These are not competing decisions — one is identity, the other is documentation.
What matters is that both are generated from the same binding, so the identity on the part can never disagree with the identity in the record.
Practical checklist before you buy a marker
- Confirm the substrate and whether the mark is applied before or after any coating.
- Get a sample marked on your actual material, then read it with the scanner you intend to buy — not the vendor's demo scanner.
- Confirm cycle time. A mark that takes eight seconds on a twelve-second takt is a line balance problem.
- Confirm the interface. A file-drop interface must use an atomic rename, or you will read half-written files.
- Price the DPM imagers for every downstream station before approving the marker.
Written by Dinesh Kumar G, ElectronIx, Coimbatore. If something here is wrong or incomplete for your process, tell us — we would rather fix it.