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Spec limits for process screening platform

Hello All,

I have a question regarding spec limits in process screening applications. For example, I have a metric for thickness of a part. The target is 0.7 with lower limit of 0.6 and upper limit of 0.8. Anything within these limits inclusively will pass. However, as shown from the plot below values of 0.8 are counted as fails. At the same time 0.6 are included as passes. 

Is there a way to control if the limits are inclusive or exclusive? Is it a setting within the preference tab or can it be done within the process screening platform on a case by case basis?

I am currently using JMP 16 but might be moving to 18 soon so any suggestions for each version would be appreciative

AdditiveRange10_0-1731955550816.png

 

11 REPLIES 11
mzwald
Staff

Re: Spec limits for process screening platform

I'm suggesting guard-banding your specs to account for the imprecision of comparing floating point values. A float64 (double-precision floating-point number) can represent real numbers with approximately 15-17 decimal digits of precision, meaning that while it can represent a very wide range of numbers, there will be a small degree of imprecision in the last few decimal places due to the limitations of binary representation; essentially, most real numbers can only be approximated with a float64, not represented exactly.

This implies the guard-band needs to be at least 1e-15.

Re: Spec limits for process screening platform

I did go back to my Python script and changed all of the float values for the spec list from float64 to float16. Using the process screen platform and imported spec limits from the spec table it seems the out of spec values are counted correctly. This might be the current workaround for this issue

AdditiveRange10_0-1732225276492.png