The web-coating process typically has a large number of separate equipment modules that need to be optimized and reproducibly controlled and measured to run successfully with good quality and costs. This results in ~2,000 variables, with critical high-impact variables that need to identified and specified in the Standard Operating Procedures (SOPs).
The total number of variables depends on the exact design of the coating line and the support functions needed. It would simplify the operation of the coater if a few of these modules could be identified as being of major importance and these were the prime focus of operating the coating line. However, all of them are important, and a malfunction or an incorrect setting of an apparent trivial module can lead to defects and operating problems. Therefore, each of these modules must be correctly set and monitored throughout a coating campaign. When the overall volume produced changes from a few high-volume products to many lower-volume products, it is essential that SOPs be modified.
This column will identify specific SOPs that should be used for all coating-process modules to ensure a quality, cost-effective finished product. All of the modules, their operating conditions and variable settings are important, and none can be ignored. Variations in process module details will often result in defects . The typical web-coating line has several general classes of SOPs that are needed to effectively operate the line.
1. Cohen, E.D., “Importance of Minor Details in Obtaining
A High-Quality, Cost-Effective Product,” Converting Quarterly, 2018 Q1, p. 66