How to Determine a Machine Capability? Shaft Fit Tolerance Measurement Results

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suzi

I'm trying to determinate a machine and process capability and I have those questions. Can I determine a machine capability measuring only one shaft with a plenty of processed surfaces, then each surface has its own fit tolerance, becouse of its cylinderity? If I can should I consider all fit tolerance measuring results for only one shaft? Or should I consider MIN and MAX measured fit tolerance for a plenty of shafts?
Is it better for the process control to use XR ratio or Xs ratio?
 
R

Rick Goodson

Suzi

This isn't my area of expertise, never the less:

Rule of thumb is that you should run 200 pieces if possible but no less than 50 for a machine capability study. One piece will not give you a time component and therefore will not show linear drift of the process. You also need to take subgroup measurements in order to get subgroup averages and then a grand average in order to determine the shape of the distribution.

Repost your question in the Tooling and Equipment Suppliers Forum. I believe you will find someone there with practical experience in machine capability studies.

Rick
 

Marc

Fully vaccinated are you?
Leader
This is an oldie, but does anyone have any contemporary thoughts on this?
 
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