Manufacturers implementing direct part mark (DPM) identification know that the quality of a two-dimensional code -- which serves as a part''s permanent identity -- can greatly affect its readability as it travels through production, the supply chain, and ultimately through to its end use. Consequently, manufacturers need 2D code verifiers for conformance and to control the part marking process. Incorporating lighting, optics, camera, part fixturing and verification software, the DPM verifier is generally deployed directly on marking equipment or as an independent station.
A DPM verifier visually inspects the quality of a direct marked 2D code by capturing and analyzing an image of the code, and rating the image on a number of quality assessment metrics. Verification provides instant feedback on mark quality for optimizing the marking process, and data for documenting that the part has been marked to a certain grade. When implementing a DPM verification system, keep in mind the following Do''s and Don''ts:
- Do define application goals. Are you implementing DPM Verification for process control, contract compliance, or both?
- Don''t confuse DPM reading with verification. The goal of reading is to locate and decode a DPM as quickly as possible regardless of code appearance, and report the results. The goal of verification is to confirm that the DPM meets an acceptable level of quality as defined by particular quality specifications and industry standards.
- Do choose the right quality assessment metrics for the job. These are based on industry specifications; AS9132 metrics are recommended for codes formed by round cells and ISO 16022 metrics are recommended for codes made up of square cells.
- Don''t ignore the fact that DPM verification standards are still evolving. A new print quality test specification currently being developed by AIM must be completed before conformance can be achieved.
- Do make sure that the verification system supports AS9132, ISO 16022 standards, and in situations where it is required for contract compliance, the verifier should also support IS0 15415. Moreover, choose a vendor that incorporates its own set of supplemental metrics into the verification system to use in conjunction with industry specifications and standards to provide additional process control metrics.