Hi all,
I'm wondering if you gals and guys can shine some light for me on an issue we are having with a True Position callout? So I'm measuring the bore diameter of a carrier, using Xact Measure True Position, set at 0 for the nominal in the the Y axis and the Z axis with a 1.2 Tolerance. My Y axis measurements are not too bad, but out of 140 pcs all the measurements in the Z axis are anywhere from 2.8 to 5.8 deviation from nominal. Even with the tolerance factored in, these parts should be considered bad, and not clean up, however, they are all within spec when scanned with the romer arm, and all clean up...??? The pencil pushers in the corporate building are asking why this dimension is so far deviated from nominal but still cleans up fine? I tried to explain but all I could come up with is "there are several things, other than my program being wrong", one of which was uncertainty, but I was told the machine is not wrong, and all other things I mentioned "should not be a factor". Upon searching I found this years 2016 Calibration report. The Factory specification is 9.1um and the results are 11.33um and the uncertainty is 0.502um. The room is temperature controlled between 68 and 71 degrees but the overhead door gets opened (and even left open) A LOT, so the temperature does bounce back and forth quite a bit, as will as the humidity level bouncing around like crazy. There are also two fans above the CMM that are always going, (different speeds...even multiple speeds a day)...all the time.
Can someone help me explain all the things that can cause this, and why.
Thanks soo much in advance.
I'm wondering if you gals and guys can shine some light for me on an issue we are having with a True Position callout? So I'm measuring the bore diameter of a carrier, using Xact Measure True Position, set at 0 for the nominal in the the Y axis and the Z axis with a 1.2 Tolerance. My Y axis measurements are not too bad, but out of 140 pcs all the measurements in the Z axis are anywhere from 2.8 to 5.8 deviation from nominal. Even with the tolerance factored in, these parts should be considered bad, and not clean up, however, they are all within spec when scanned with the romer arm, and all clean up...??? The pencil pushers in the corporate building are asking why this dimension is so far deviated from nominal but still cleans up fine? I tried to explain but all I could come up with is "there are several things, other than my program being wrong", one of which was uncertainty, but I was told the machine is not wrong, and all other things I mentioned "should not be a factor". Upon searching I found this years 2016 Calibration report. The Factory specification is 9.1um and the results are 11.33um and the uncertainty is 0.502um. The room is temperature controlled between 68 and 71 degrees but the overhead door gets opened (and even left open) A LOT, so the temperature does bounce back and forth quite a bit, as will as the humidity level bouncing around like crazy. There are also two fans above the CMM that are always going, (different speeds...even multiple speeds a day)...all the time.
Can someone help me explain all the things that can cause this, and why.
Thanks soo much in advance.