Using Direct Part Mark (DPM) technology to apply bar codes to a part is a small piece of the larger system that needs to be considered. Marking the part is less than half of the system – reading the part is a much bigger consideration and far more difficult.

Most of the DPM solutions create a bar code mark that provides only a low contrast differential from the surrounding material – a grey-on-grey situation – and for an optical technology like bar code this makes reading very difficult. A manufacturer who marks the part when it is brand new may have no understanding of what his Customer has to go through to read that same part when it is in-service and dirty.

The whole system of marking and reading in the real world has to be considered before making a final choice on which DPM technology to use on which part so that it will be usable for many years in actual service.

DPM technology solutions take two basic methods: Non-intrusive and Intrusive technologies, each with their strengths and weaknesses, to be considered below:

Non-intrusive Marking Methods

Marking methods that are non-intrusive to the material are produced as part of the manufacturing process or by adding a layer of material to the surface using methods that have no adverse effect on material properties. These methods include:

  •     Ink jet
  •     Laser bonding
  •     Laser Engineered Net Shaping (LENS)

Less popular and/or successful methods:

  •     Silk screen
  •     Liquid metal jet
  •     Stencil
  •     Automated Adhesive dispensing
  •     Cast, forge, and mold

Intrusive Marking Methods

Intrusive marking methods alter a parts surface (abrade, cut, burn, vaporize, etc.) and are considered to be controlled defects. If not done properly, they can degrade material properties beyond a point of acceptability. Consequently, some intrusive markings, especially laser, are generally not used in safety critical applications without appropriate metallurgical testing. Typical intrusive marking methods include:

  •     Dot peen
  •     Direct laser marking
  •      Electro-chemical etching

Less popular and/or successful methods:

  • Engraving/milling
  • Fabric embroidery/weaving
  • Abrasive blast