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Vector Deviations gone awry

mjdevries
I received data from a PC-DMIS cmm and was reviewing it. We receive the data with the XYZ and the Vector deviation information. I was reviewing this data and I noticed that the vector deviation was much larger than the sqrt of the sum of the squares of the coordinate deviations, AKA, the absolute deviation. I reviewed the PC-DMIS program and found that the nominal in the CALL/EXTERN statement did not match the feature declaration statement which defines the nominals that are used in the X, Y, and Z outputs. I'm assuming the CALL/EXTERN statement defines the vector measurement from the nominal point in the call statement. Does this make sense?

F(M1)=FEAT/POINT,CART,590.878, -687.587,662.998,0.0459841,-0.998654,0.0239917
CALL/EXTERN,DMIS,M(PCD_AUTO_VECTOR_POINT_605),(M1),590.878, -690.59,$
662.998,0.0459841,-0.998654,0.0239917,VEC,0.0459841,-0.998654,0.0239917,$
0.0459841,-0.998654,0.0239917,'THEO_THICKNESS',0,'NO','NO',0
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  • I believe I finally figured out what went wrong with these outputs. The program is setup to check all of the CMM points using the global alignment. Subdatum alignments are created through out the program, but they are not used when measuring the part. The cmm operater instead put all the output statements at the end of the program and set the alignments prior to the outputs. So the data was collected with the global aligment, but outputs were calculated from other iterative alignments. I do not think I would see such bizzarre data if the iterative alignments were used also when the part was checked.
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  • I believe I finally figured out what went wrong with these outputs. The program is setup to check all of the CMM points using the global alignment. Subdatum alignments are created through out the program, but they are not used when measuring the part. The cmm operater instead put all the output statements at the end of the program and set the alignments prior to the outputs. So the data was collected with the global aligment, but outputs were calculated from other iterative alignments. I do not think I would see such bizzarre data if the iterative alignments were used also when the part was checked.
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