Jay, I'm sorry to say that I can't locate my copies of the VDE/VDI standards or CMMA. I must have archived them during a past clean-out. I can tell you, however, that Zeiss makes extensive use of VDE/VDI standards, and you can probably obtain a copy from the Zeiss Brighton MI office at (248) 486-2670, or from 3D Control Inc (Zeiss Technicians) at 612-494-0703.

Basically, VDE/VDI requires the use of certified gage blocks of various lengths. You create a plane by probing one end of the gage block (using the CMM software) and then travel to the opposite end of the gage block, take a point, and ask for the perpendicular distance between the point and the plane. The result must not differ from the known gage block length by more than the published specs of the CMM.

The advantage of this method is that it tests
all elements of the CMM, including the bi-directional operation of the CMM probe head. The gage blocks are oriented both parallel to each machine axis (1D), and finally at a 30 degree angle inclined to all three CMM axes (3D). The result is expressed as an uncertainty (U95) in which at least 95% of the results fall within specifications. Ideally, you would take 20 measurements in each location, and be allowed to throw out any one "flyer".

Please note: It's important to be sure that the gage blocks are supported correctly, so as to minimize any measurement error caused by sag in the blocks.

Hope this helps.

Mark Osterstock
Q-Mark Manufacturing, Inc.
home page: www.cmms.com
e mail : mark@cmms.com