Abstract: Based on the rotation tool center point (RTCP) function of NC system, R-test device has been used in accuracy inspection of multi-axis movement and calibration of multi-axis machine tools. Three linear displacement sensors are used in this device to measure the sphere center in X, Y, and Z directions of a reference ball attached to the machine’s spindle, thus the tool center point (TCP) can be measured during the machine’s multi-axis movement. Based on the analysis of measuring principle, a structural optimization method for R-test device is obtained. Two indices thus maximum measuring space and measuring sensitivity are designed to evaluate the measuring performance, and the numerical algorithm of these two indices are also got. By analyzing the restraint state of the measuring limbs and the measured ball, the design ranges of two key dimensions thus the diameter of the measuring limbs’ located circle on the reference plane and the angle between the measuring limb and the reference plane are got. In the condition of choosing the normal ball-bar and length measuring meters, these two key dimensions’ optimal solutions are calculated by Monte Carlo method, and the structure optimization is finished. Simulation shows that this R-test device has the best measuring sensitivity and the maximum measuring space which is larger than a spherical space whose radius is 4 mm, and it can satisfy the actual need of measuring accuracy and size.

Key words: Accuracy inspection, Five-axis machine tools, R-test, Structure optimization