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Question
#42
Subject: Which type of control card (SPC) could we use for the barriers proprieties (OTR, WVTR, etc.) on the metallizing products?
Which type of control card (SPC) could we use for the barriers proprieties (OTR, WVTR, etc.) on the metallizing products?
Answers (links jump to full text of answer below)
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#43
Author: Eldridge Mount, AIMCAL
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Subject: You should chart data taken from several positions across the face of the roll you are testing
For SPC Charting of metallized barriers, you should chart data taken from several positions across the face of the roll you are testing. This should be at least three locations on all width rolls. Five positions is better but some times hard to justify unless you are only doing wide rolls. The sub group number should always be the same irregardless of width to allow data comparisons. You should start to collect the data and chart using the average and range until you have approximatly 30 sets of data. Then calculate the average standard deviation and compare with the film performance requirements to determine your process capability. At that point you can decide to continue with the range plotting or change to a refined measure of the variability.
When you begin the data comparison you may want to start by comparing top and bottom of the roll as the top coming out of the chamber will usually be better than the top of the rewound roll due to extra winding and lower pressure in the chamber at the end of the run. You should also, in my opinion, control chart chamber pressure.
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