Just when it seemed that the art of printing barcodes on labels and packaging materials was under control, a new challenge is presenting itself to a new category of barcode applications. DPM, direct part marking, barcodes that are permanently placed on an object.
More and more, in industries such as medical device, automotive and aerospace, it is necessary to etch a barcode directly onto a part. In these applications, where a barcode printed on a label won’t work, laser etching or dot-peen methods are used. Unlike a high-quality label material, a barcode marked directly onto a part is subject to the characteristics of the material that the part is made of.
Let’s talk about some examples of products and industries that require the use of DPM collectively known as “direct part marking”. An implantable medical device such as an artificial knee can’t use a conventional printed label, and the material that is necessary for the medical device to fulfill its primary function must be used as the background for the barcode. Other medical devices, although not implanted must survive repeated cleaning cycles. Other environments in which a label could not be used are automotive or aerospace engine parts in which the barcode must survive the high temperatures that the part is subject to.
The solution is to “build in” the barcode through various techniques. Laser etching is one of the most common DPM techniques and can usually be used successfully to produce excellent results, as long as the process is controlled in the manner required by the material being marked. It is interesting that laser etching itself is not really just one technology or technique. Different setups for a laser etching process yields vastly different results on a given type of material. The results can range from a completely unreadable code to one that is not only easy to read but can get an “A” grade when verified. This is why laser etching equipment has many setup variables that users can change for each material that they encounter. A barcode verifier designed specifically for DPM symbols can also be used as a gauge tool for the laser etching equipment. Thus, the key to successful DPM barcoding is to learn what works for each particular material and/or part by using a barcode verifier to report readability and optical properties to the laser etching operator for use in further adjusting the process. Operators often do not realize how many variables they’re dealing with and typically will not hit upon the best, or even an adequate, setup to achieve a good barcode without this feedback loop.
A great system I saw recently for determining the best laser etching setup, actually produced an array of test squares very quickly so you could see at once the results from a variety of settings combinations. Simply putting this test pattern under one of our DPM verifiers, and cycling through the available lighting options on the DPM verifier quickly identified the best candidate(s) for barcode production. We then chose the one that “looked” best and produced a barcode and “voila” – an “A” grade code. We used the IM DPM grading standard (also known as ISO/IEC TR 29158) which gives a good correlation to DPM enabled barcode readers.
Another common marking technique is called Dot Peen. Dot-Peen is the process of indenting the material with small dots into a material’s surface. In this process, there is no real change in color or reflectivity of the surface, but the angle of the indentation causes the light from a barcode reader to reflect differently from the dots compared with the background surface. Because the angle of reflection from the dots versus the background surface is the source of the image of a dot peen symbol, the surface texture is often a critical factor to successful dot peen results. If the texture of the surface mimics the angles in the dots themselves, then the dots will not be distinct from the background texture.
A passing grade of “A” (or even a lower grade such as B or C) indicates that a barcode is produced properly and will be readable down the line when received by others.The grade given by the barcode verifier also certifies that you’ve met industry standards, which are required in many industries. Industries requiring this type of compliance include UDI (Unique Device Identification a medical device rule from the FDA) and UID (MIL-STD 130, a government standard used in military applications).
In the past, DPM barcode verification was challenging for many reasons. But we have recently introduced some new products that simplify the process. Our new TruCheck FlexHite DPM barcode verifier holds the verifier for you – suspended above your part – and enables you to easily position it to the correct focal distance above your object, without literally performing a balancing act. This new product takes the same verification platform as the TruCheck 2D USB DPM on which it is based and adds the adjustable height stand and patented laser focus indicator (thus the name “Flex-Hite”) to make the verification process a little bit easier than before — especially for small or irregularly shaped parts were resting a verifier on the object would be difficult or impossible.
We see that DPM barcode production is increasing in several industries and that DPM barcode verification will continue to increase in importance and value. An ever-increasing variety of materials and ever-smaller DPM symbol features will test the limits of equipment capability and challenge equipment operators to find the best setup parameters.
Conventional barcodes have been verified to avoid costly reprints and wasted materials – but the fundamental process of printing – was known. DPM barcodes on the other hand, are almost always a process of discovery. And, talk about the cost of reprints! Directly marking a permanent barcode onto an expensive component has to be the last step in a successful process, not a costly waste. Contact one of Webscan’s barcode experts to for advice on how to achieve the best DPM marks for your product.