Readability is a measure of how easy or difficult it is for a direct part mark identification (DPMI) reader to successfully read a code. If a code is not readable, the part is not processed and the production line stops. Until recently, manufacturers implementing DPMI have lived with varying levels of read rates, in some cases approaching the upper 90 percent level. However, this level of performance is no longer acceptable.
Today, Six Sigma read rates--a level of quality that equates to only 3.4 missed reads per million opportunities--are essential. To ensure these results, it is important to plan, understand and implement a marking system that builds in quality. A user looking to implement DPMI must understand all the factors that affect the readability of the code. A good baseline for this is to understand the design of the Data Matrix symbology and associated issues that might affect readability.