ISO compliance: Corrective and Preventive Action in Barcode Quality
There has been an interesting and helpful discussion taking place in the LinkedIn ASQ group. The topic is the difference between a corrective action and a preventive action in manufacturing quality—not specifically barcode-related but very applicable.
Regarding ISO compliance in barcode quality, the root issue is conformity and non-conformity. What exactly is a conforming barcode? What is a non-conforming barcode? I often encounter people in this industry who don’t have a ready answer or understanding of these questions.
The ISO 9000 definition of a corrective action is one which fixes the non-conformity, whether it be a repair or a rebuild or whatever. But what is conformity or a non-conformity?
ISO Compliance is the basis for barcode verification
In the world of barcoding, ISO compliance is defined by a set of ISO specifications. For linear barcodes that specification is ISO 15416; for 2D symbols the specification is ISO 15415 to test the quality of a printed barcode or symbol image. These specifications define how a compliant barcode or 2D symbol must perform in terms of a set of test criteria or parameters. For linear barcodes, this includes such things as symbol contrast, modulation, decodability and defects. For 2D symbols this includes such things as Axial Non-Uniformity, Grid Non-Uniformity, Unused Error Correction and Fixed Pattern Damage. These form the basis for the verification of the printed barcode or symbol.
Because a verifier is a test instrument, it is also necessary to ensure its accuracy as a gage. This is done by testing the verifier using a calibrated conformance test standard with known performance values to which the verifier must comply, within specified tolerances.
ISO Compliance is important for the barcode image and for the verifier
The verification report measures, evaluates and grades the symbol against the ISO compliance parameters. It does not explain why a particular parameter is downgraded or suggest how to improve it. This is often confusing and off-putting to a user who is looking for a simple solution. Considering the numerous ways in which a symbol can be imaged, whether it be a flexographic, lithographic or letterpress process, a thermal or thermal transfer process, a screen printing process, a laser or chemical etching process, or some other reprographic process, the range of possible causes for imaging problems is enormous. A verifier can only point to an actual attribute of the image; it is assumed the operator can interpolate the verifier test results in terms of his own imaging process to decide on corrective actions.
ISO Compliance does not explain how to improve the reprographic process
These corrective actions should eliminate the non-conformity that the verifier has found and reported. Properly applied, this corrective action should eliminate the cause of the non-conformity and therefore also act as a preventive action.
While this might seem highly technical, it is the only way we have of “leveling the playing field” so that we have a common language and way of describing what is required and expected of the barcode, which is so ubiquitous and essential in the supply chain and elsewhere.