Comparison of the Measurement Capabilities of CMM and AA-CMM Machines in Flatness Verification

Manufacturing is among the most important activities contributing to the nation’s economy. Almost everything we see, use, and touch, was made by someone, and now more than ever, quality is paramount across the industry. It is virtually impossible to fabricate perfect parts, and thus it is accepted to have variation in part dimensions specified by acceptable tolerances. For flatness, this tolerance will be the intended smallest variation of material form in a plane of a part. To control those variations and guarantee that the part will function as intended in an assembly, measurement verification must be conducted with specialized metrology equipment. The Coordinate Measuring Machine (CMM) and the Articulated Arm CMM (AA-CMM) are analyzed in this study, to identify their respective advantages and disadvantages in flatness measurement. Therefore, the goal of this pilot study is to identify the measuring limitations of each machine, to propose a methodology to identify appropriate use of each device based on its capabilities. Simple experiments were designed, and flatness measurements made. As expected, it is observed that the CMM performs better than the AA-CMM in flatness measurement. A more detailed statistical analysis must be made in the future to identify the quantitative differences in the use of these instruments, so that the versatility of AA-CMM in Geometry verification could be investigated. Keywords: CMM, AA-CMM, Laser Point, Metrology device selection, Measurement boundary, Flatness verificatio