Evaluation of coordinate measuring machines

A method which evaluates large coordinate measuring machines (CMM) and estimates their measuring capabilities within a specified work volume was developed and implemented. Five CMMs were selected for evaluation. The methodology used to evaluate them, along with the test results, were discussed in a previous report. The data reduction method previously used was found to have several restrictions that limited its usefulness. A new method which has been implemented is discussed in this report. Three of the machines previously evaluated have work volumes far in excess of the standards previously used. A larger standard was designed, fabricated, and used to obtain the data required to complete the project goal. This device was used to estimate the precision and uncertainty of the three large CMMs. The results are reported. A technique which uses a small ball plate at several locations to estimate capability was tested on one of the three machines. The results were compared with those obtained with the large ball plate. The results were almost identical, but the recommended calibration method is to use a standard that covers the work zone of the CMM being evaluated.