Knowledge · DPM

What is DPM code reading?

Direct Part Marking (DPM) puts a Data Matrix or similar code permanently on the part itself. Reading it reliably is a Computer Vision optics problem first, a decoder problem second.

Direct Part Marking on metal

Definition

DPM is the mark on the part

Unlike a printed label, a DPM code is laser etched, dot peened, ink jetted or otherwise applied to metal, plastic or coated surfaces. Traceability stays with the part through machining, washing and assembly, which is exactly why the optical signature is often difficult.

  • Codes can be shallow, shiny, incomplete or sitting on a curved surface.
  • Background and mark may share similar reflectance under the wrong light.
  • Production speed and part presentation change the usable exposure window.

Why it is hard

Contrast, curvature and motion

A smart code reader can only decode what the optical path delivers. For DPM, that path is usually the bottleneck.

Contrast

Low cell-to-background difference on brushed or coated metal needs directional or dome-like lighting, not brighter ambient light alone.

Curvature

Cylinders and castings warp the projected code geometry. Working distance, FOV and angle matter as much as resolution.

Motion

Moving parts need exposure control, triggering and sometimes strobe lighting so the code stays sharp for the decoder.

Method

Lighting first, then reader family

Stabilize the image of the mark before you compare MV-ID families or software tools. Read rate and grade claims without your parts and lighting geometry are not a selection method. Feasibility starts with samples under representative presentation.

Computer Vision lighting Smart code readers