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Question calculating process capability on box sortation system

Question calculating process capability on box sortation system

Question calculating process capability on box sortation system

Greetings fellow IE's,

I work for a distribution center where we have a sorter system that scans boxes from overhead and diverts the boxes down the shipping lanes and to the trailers.  I am trying to calculate the Cp/Pp,Cpk/Ppk, but am having trouble figuring out if my Cp is accurate.  I am calculating Cp on "no-reads" (failed scan reads) that are recirculated and passed through the scanning tunnel again until there is a read.  Our volume fluctuates between 50k-120k thorughout the year and of course with the higher volume we have more no-reads.  How can I determine an accurate Cp?  If volume was a constant it would things easier, but is not.  I thought of isolating no-reads for volumes at 50k, 60k, 70k, etc, but I do not believe it will truly give me an accurate Cp.  The range is still quite large.  Any feedback would be greatly appreciated.  Thanks.

RE: Question calculating process capability on box sortation system

I think you need an Xbar - R chart, a chart that tracks variable data along a continous scale.

RE: Question calculating process capability on box sortation system

If you used a p-chart, which would chart the fraction or percent of non-conforming events – no reads, then you should be able to first see if you have a stable continuous distribution.  This type of charting would help you deal with the changes in volume.

RE: Question calculating process capability on box sortation system

Thank you for the responses so far.  Please keep them coming.

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