Duramax

[[Ja...]]

I ran a part on our new Duramax last night and it ran great but had some dimeters out of spec. SO the operator had it run on our Eclipse machine and there is a .002 difference between the 2 machines.

The Duramax machine is in a room that is 75 degrees and fluxuates and the Eclipse is in a room that is 68 degrees and plus or minus 2 degrees.

The duramax has the temp sensors on it, but I am not super familiar with the temp aspect of it, as I have never used it on any CMM until now.

Not sure what is causing the difference.

any feedback would be appreciated.

[[De...]]

A lot of variables go into making a determination when trying to make a determination on why results are varying on two different machines.

First when you say .002 are you saying .002 inches or .002 millimeters?

0.002 inches is substantially different than 0.002 millimeters.

You brought up temperature, what is the part material? Also what is the size of the feature being measured?

Variations in size measurements caused by temperature are determined by the material Coefficient of Thermal Expansion (CTE)
for the material which is the amount of growth to be expected per degree of temperature per linear unit of measure.

The amount of material movement can be determined by taking the CTE * Difference in Temp from Spec * Size of measurement, care must be taken to assure measurements are all in the same unit as the CTE is specified when doing calculations.

This means that larger features will have more variance in measured size than smaller features, it also means the amount of movement will be greatly effected by the material the part is made from.

All that said, are both programs identical? Scanning on one versus probing points on another could make a big difference.

How is the part itself? is there form error in the features being measured?

Are the probes being used the same?

Is the part held the same way in both machines?

Have you checked the probes for problems?

All of the above can influence your results and therefore can be part of the cause for two machines to give differing reasons.

In order to track down the source of the error you need to make every reasonable effort to assure that the measurements are done the same on both machines, once you have eliminated all differences, whatever is left must be the cause.

With very small variations between machines it can often come down to the machine specification allows more error on one machine or the other machine than another and allowable tolerance errors in the machines, and temperature as you stated.

For a variance of .002 mm it might be something like that, if its 0.002 inches I would be looking for something more substantial like probe or part movement loading error, shanking etc.