Direct Part Mark (DPM) Code Reading

2020-04-10 21:27:53 Dan

What is DPM Codes?

Direct Part Marks (DPM): they are codes, symbols, and text that are etched or printed directly onto the surface of a part instead of affixed by a label.  DPM codes, which are most commonly Data Matrix or QR codes, are used for track and trace purposes in a variety of industries, particularly automotive and electronics manufacturing.

It is a fixed part of the product. The product is identifiable throughout the entre lifecycle, so it can be traced back, and it will not cause interference when the product continues to process. When parts are in unfavorable or severe environmental conditions, and other marking methods are not available, "direct part identification" can realize permanent parts tracking. So as to reduce downtime, overhead and costs, while improving the efficiency of the enterprise.

The main advantages of DPM codes: they are permanent and cannot be easily removed, obscured, or damaged.  DPM codes are also a popular choice for parts with textured surfaces (label will not stick) and very small parts (label will not fit). Because DPM codes last as long as the part itself, the piece can be identified easily identified throughout its entire lifecycle, also known as "cradle-to-grave" traceability.

Extremely Challenging codes: However, DPM codes can be extremely challenging to read due to poor contrast, so finding a DPM code reading solution is essential for reliable identification.

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DPM Code Generation

The generation of DMP codes is called marking. Marking means that directly machine printing, cast or etch the symbol on the part, and uses a process that meets the requirements of the manufacturer, supplier or regulations to directly mark the "permanent" symbol on the item or part . There are four methods: Laser Etching, Machine Impact, Inkjet Printing and Chemical Etching.

Laser Etching: The advantages of laser etching are high quality, very high resolution, non-contact and permanent.

Machine Impacting: The initial cost is relatively low, it is portable and permanent.

Inkjet Printing: Very high speed, low initial cost, can be completed with non-contact.

Chemical Etching: Low initial cost, does not change the surface of the object, regardless of size.

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Most Challenges of DPM Code Reading

Low-contrast, Variability, Curved Surfaces, Reflective Surfaces, Imperfect Surfaces and Codes on Small Objects

Since the DPM codes are etched directly onto the part, DPM codes are very low contrast compared to traditional black barcodes printed on a white background.  Plus, there can be significant variability in DPM codes, where and how they are printed on a surface, and features of the surface itself that can significantly impact code readability. 

For example, many DPM codes are etched onto reflective, curved, or uneven surface which can be very challenging for barcode readers to identify reliably. 

Also, the surface is rarely uniform, meaning that it may also contain granules, stripes, streaks, or other irregularities and imperfections that can further interfere with reliable code reading. 

Advanced imager-based code readers use special DPM code reading algorithms to solve these applications reliably.  Besides, low angle lighting or the use of different color LEDs can be used to create additional contrast and improve code visibility.  

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