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CMM Calculator


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I have created two calculators that I find handy. I am not sure if they will help anyone but I made them in order to allow me to do some simple calculations without having to keep having to do them out long hand.

The first is a MPE e0 calculator, it allows you to use your machines spec to calculate the allowable error at a given distance. This is handy for determining the uncertainty inherent in any given measurement.

The second calculator lets you calculate the amount of compensation that needs to be applied to a given measurement based on the known temperature at a given nominal size with given coefficient of thermal expansion. (It also shows what 10 percent of that value is so it may be used to help determine uncertainty of a given measurement, given as from my research NIST suggests that any CTE is inherently inaccurate unless it has been determined through tests completed on the actual part to be measured.)

I created these because I was often calculating this information when someone wanted to know 'how accurate is the machine' or 'how do we know this is accurate'. With different temperature scales, different values for the CTE whether in metric or not, as well as measurements in metric and inch I found it tedious to complete these longhand and so created these calculators as a shortcut.

I figured this would allow me to give a definitive statement regarding any specific measurement that this measurement is XXX and is accurate within +/- xxxx amount based on the machine having a valid calibration that is within manufacturers specifications.

To the best of my knowledge these should not have any issues, however if anyone notices something incorrect please let me know so I might fix it. Hope these can be helpful.

CMM_Calculator.xlsm

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  • 4 years later...

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This is the actual formula for a B&S CMM.
(2.00 + 3.00 * L/1000)
I've never seen it this way.
Typically, its: (2* L/1000) (Example)
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