The report from PC-DMIS says the part is
But PC-DMIS "nominal"
points compared to the CAD model
by our software from inside the CAD system show something else
How does the part actually look?
Best fit results. Actual part is
Profile tolerance 0.100 mm
Units - whiskers are deviation x 10
green whiskers - in tolerance
green curve - nominal geometry
red whiskers - missing material
red curve - lower spec limit
blue whiskers - extra material
blue curve - upper spec limit
Small (25.0 mm diam) die insert.
Inspect the profile of the part with 0.100 mm tolerance.
This company used IGES file to inspect this part in PC-DMIS. The first
picture represents comparison between the "nominal"
points generated by PC-DMIS and the nominal CAD model. We used our own SPV to evaluate how
far the "nominal" points are from the CAD surface
inside Unigraphics®. The second image shows the results as
reported by the third party software. Then we checked and best-fitted the actual center-of-probe points to the CAD model
PC-DMIS reports the part being oversized despite
the fact that it was recut number of times. In reality the part is undersized,
with a mean of -0.037 mm after best fit and 34 (out of 179) points below the lower
tolerance of -0.050 mm. The real reason is that the CMM software
did not interpret the IGES file properly and all "nominal"
hits where generated off the actual surface anywhere from -0.058 mm all the way down to
-0.111 mm. On the other hand the NC cutter path was generated inside UG. Is IGES any
good? Sometimes, but when there is a problem you wouldn't even know.
Eliminate loss of accuracy and reduce scarp by using