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Reduced sampling plan for a continuous process

From: Carl Richard
Date: 21 May 2002
Time: 13:51:16

Comments

How does one set up a skip lot sampling plan for attributes for a continuous process like papermaking? The machine does not produce discrete lots like widgets, so isolated lot schemes would not work. Instead, the process makes a continuous stream of material 24 hours /day. The process does produce large jumbo or master rolls we call sets. These rolls are taken to rewinders and converted into smaller rolls for our customers. We sample roughly 100 sq. yards off a jumbo and visually count defects like dirt, holes, etc. and normalize the results to defects/100 sq. yds. Thus we get an output of data by attribute type. We have upper control levels for the attributes based on a Poisson. When any attribute exceeds the upper control limit we put product on audit for re-inspection. We now do each jumbo roll and want to reduce, if possible, the frequency of testing. A review of our history for 6 months indicates, on average, about 2% of the jumbos we test are out of control.

Any suggestions?


Last changed: November 20, 2007