Trouble shooting a Failed Check

When a check fails, it will report two values for troubleshooting purposes: the Measured Deviation and Distance Out of Tolerance . The first number (0.0208) is the Measured deviation or the size of the tolerance zone required for the part to pass. The second number (0.0128), is the distance out of tolerance or the necessary expansion of the tolerance zone in order for the part to pass. For the above profile check, the sum of the check tolerance plus the distance Out of tolerance will equal the Measured deviation (0.008+.0128=.0208).

By convention, Position checks are reported differently. The Distance Out of Tolerance is reported as the distance the drill would have to move for the check to pass, the sum of the check tolerance plus two times the Distance Out of Tolerance will equal the Measured Deviation(0.008+2*0.0039=0.0158).

If a check fails check the following:

  1. First consider to what extent the check failed. If its large, check the datum alignment and transform. If the error is small check your fit residuals.

  2. Within the Summary table is a “Fit Transform” section. Check to see if the transform is close to zero. If not, check the datum settings to verify that the alignment is set up correctly. Its of- ten helpful to align to the evaluated position to see what’s causing the issue.

  3. The Summary table also tells you how well you data fit the datums. By checking to see if there was a bad fit to one of the datums you will see if the datums are contributing significantly to the error.