A modular space frame for assessing the performance of co-ordinate measuring machines (CMMs)

In the present investigation, a new form of space frame for rapid verification of co-ordinate measuring machines (CMMs) is proposed and applied. This space frame has the form of a tetrahedron and is referred to as a modular space frame as different configurations of tetrahedron can be obtained easily and rapidly. The modular space frame comprises magnetic ball links and a ball plate. A typical magnetic ball link consists of two magnetic cups and a carbon fiber link, connecting magnetically, two high accuracy spheres. The volumetric error data obtained when a CMM measures the calibrated modular space frame can be used to verify whether a CMM maintains the manufacturer specifications. The experimental results have demonstrated that the modular space frame system has an acceptable repeatability and provides a practical and cost effective mechanical artifact to determine the volumetric accuracy of small/medium sized CMMs. The developed technique can be applied for calibration, verification, periodic reverification and acceptance test of any type of CMM.