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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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  • It's 3mm out of the part material. My CMM operator may have deliberately put the target point out of material because this is 1370 mm wide plastic injection molded part. We have huge tolerances compared to what most of you see.

    I also found that there was an alignment that may also have caused some of the oddities that I'm seeing, but it still would not explain the vector value being so much larger than the absolute deviation.
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  • It's 3mm out of the part material. My CMM operator may have deliberately put the target point out of material because this is 1370 mm wide plastic injection molded part. We have huge tolerances compared to what most of you see.

    I also found that there was an alignment that may also have caused some of the oddities that I'm seeing, but it still would not explain the vector value being so much larger than the absolute deviation.
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