I am having some trouble with measuring accurate Diameter size, I have read some threads on this type of thing but the solutions provided pertain to mostly Bridge Type CMMs and I am using a Romer Arm. So I'm interested in any tips you guys may know of to get more accurate results. ... oh and it seems I have more trouble when working on sheet metal parts and I can imagine its due to the thickness of the material. Thanks in Advance
I have been using a Romer Arm for more than six years now, and they just don't do diameters better than +/-.001". I've done many side by side comparisons with a Bridge type CMM, and while the arm will measure within a +/-.0002 when measuring position or profile on a small volume part, diameters are always inconsistent. This is not unique to PC-DMIS as I have had the same results with other software. I think it may be due to how it calculates diameters with six or seven axes in play, versus two with a standard CMM, but I may be wrong.
One thing I have found is that when calibrating to a sphere, I get varied measurements. The single point calibration always gets me the best results. With single point calibration, you are using the full rotation of the six and seventh axis, instead of holding the arm straight up with a sphere calibration.
Not as extensively as I have with probing. The accuracy will vary depending on a multitude of factors (part color and finish, operator, ect.). If you have a +/-.010 call out, scan away. Auto Circle extraction works well once it is setup, it may require some tweaking at first, but is well worth it if you are establishing a program to measure a large number of parts. My only gripe with scanning in PC-DMIS is the lack of filtering features found with other types of software, there tends to be a large amount of artifact which does alter results.
Not as extensively as I have with probing. The accuracy will vary depending on a multitude of factors (part color and finish, operator, ect.). If you have a +/-.010 call out, scan away. Auto Circle extraction works well once it is setup, it may require some tweaking at first, but is well worth it if you are establishing a program to measure a large number of parts. My only gripe with scanning in PC-DMIS is the lack of filtering features found with other types of software, there tends to be a large amount of artifact which does alter results.
