I have a PPAP from a supplier where the compression spring force MSA is not for the actual spring, the supplier said they used a 'stable spring' as this validates the force measuring system rather than the variation in using the actual part number being PPAP'd.
I have requested the MSA on the actual spring, but can anyone testify to the suppliers argument that 'some' spring designs are not initially repeatable / stable. I'm told a spring is set by compressing to close the coils then released, initially when compressed it returns to 95% of its original free length. When compressed a 2nd time 97% of free length, then after being compressed 5 or more times it recovers to the same length, more compressions = more consistent free length becomes. As the spring length stabilises so does force measurement.
The actual production process only requires 1 set (that's what we are paying for), so to stabilise (compress x10) the spring before the GR&R is not production representative. What would you do, I expect the new MSA on the actual spring will show the variation initially but then improve throughout the study?
I have requested the MSA on the actual spring, but can anyone testify to the suppliers argument that 'some' spring designs are not initially repeatable / stable. I'm told a spring is set by compressing to close the coils then released, initially when compressed it returns to 95% of its original free length. When compressed a 2nd time 97% of free length, then after being compressed 5 or more times it recovers to the same length, more compressions = more consistent free length becomes. As the spring length stabilises so does force measurement.
The actual production process only requires 1 set (that's what we are paying for), so to stabilise (compress x10) the spring before the GR&R is not production representative. What would you do, I expect the new MSA on the actual spring will show the variation initially but then improve throughout the study?