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Why are standard operating procedures needed for web coating? Part 4 of 4

By Dr. Edward D. Cohen 
 
The typical web-coating line has several general classes of SOPs that are needed to effectively operate the line. They include:
 
Solution Preparation Process [2]:  Specifies the mixing kettle to be used, solution temperature, impeller speed, mixing time, addition method of raw materials,  addition time, unique steps that may be need for certain products, quality-control tests at mixing completion, and corrective action that may be needed if some aspects falls out-of-limits.
 
Solution Delivery [2]: Specifies hardware configuration, solution flow rate to coating applicator, solution temperature and viscosity, filtration, deaeration, and cleaning procedures.
                 
Coating Process SOP [2]:  Specifies the exact process variables needed to apply the solution to the substrate. Each product should have a unique SOP. This will increase the ability to optimize individual products to obtain the best performance.
 
Process Hardware SOP: Specifies the process-variable settings and allowable range during coating for all of the coater components.
 
Coater Subsystems SOP: Each individual component has several hardware systems required for it to function as intended.
 
Product Testing SOP: Each of the QC tests used to accept a product is described. This ensures that all production sites are conducting the tests in the same way. External reference as to the basis of the tests can be included.
 
Standard testing procedures are available from ASTM. Table 3 lists some available coated-related procedures. Using ASTM standard-test methods is more efficient than developing them as needed and will ensure that test results are compatible with the converting industry
 
It is more effective to have SOPs for each web-coating process as opposed to one SOP for the entire coating line itself.
 
Summary
Using Standard Operating Procedures for the web-coating process will ensure that the coating line operates at peak efficiency because all components are functioning at the specified conditions, improving coating quality, yield and reproducibility.
 
References
2. Cohen, E.D. and Lightfoot, E.J., “Coating & Solidification,” in J. Greener, G. Pearson M. Cakmak, Roll-to-Roll Manufacturing: Process Elements and Recent Advances, John Wiley & Sons, 2018

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