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The R-test is an instrument to measure three-dimensional displacement of a precision sphere attached to a spindle relative to a work table by using three displacement sensors. Its application to error calibration for five-axis machine tools has been studied in both academia and industry. For the simplicity in calculating the sphere center displacement, all conventional R-test devices use contact-type displacement sensors with a flat-ended probe. Conventional contact-type R-test may be potentially subject to the influence of the friction or the dynamics of supporting spring in displacement sensors particularly in dynamic measurement. This paper proposes a non-contact R-test with laser displacement sensors. First, a new algorithm is proposed to calculate the three-dimensional displacement of sphere center by using non-contact displacement sensors. The compensation of measurement error of a laser displacement sensor due to the curvature of target sphere is incorporated. Then, the measurement uncertainty of four laser displacement sensors with different measuring principles is experimentally investigated in measuring the geometry of a sphere in order to select the laser displacement sensor most suitable for the application to a non-contact R-test. A prototype non-contact R-test device is developed for the verification of the proposed algorithm for non-contact R-test. Experimental case studies of error calibration of 1) static *Manuscript Click here to view linked References 2 and 2) dynamic error motions of rotary axes in a five-axis machine tool with the developed non-contact R-test prototype are presented. Its measurement performance is compared to the conventional contact-type R-test device.

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Position and orientation errors of rotary axis average lines are often among dominant error contributors in the fiveaxis kinematics. Although many error calibration schemes are available to identify them on-machine, they cannot be performed when a machine spindle is rotating. Rotary axis location errors are often influenced by the machine's thermal deformation. This paper presents the application of a non-contact laser light barrier system, widely used in the industry for tool geometry measurement, to the identification of rotary axis location errors, when the spindle rotates in the same speed as in actual machining applications. The effectiveness of the proposed scheme is verified by experimental comparison with the R-Test and a machining test. The uncertainty analysis is also presented.

Thermal distortions are regarded as one of the major error factors in machine tools. ISO 230-3 and ISO 10791-10 describe tests to evaluate the influence of thermal distortions caused by linear motion and spindle rotation on the Tool Center Position (TCP). However, for five-axis machine tools, no thermal test is described for a rotary axis. Therefore, in this paper, a method for observing thermally induced geometric errors of a rotary axis with a static R-test is proposed. Unlike conventional thermal tests in ISO 230-3 and ISO 10791-10, where the thermal influence on the positioning error at a single point is tested, the present test measures the thermal influence on the error motions of a rotary axis. The R-test measurement clarifies how the error motions of a rotary table change with the rotation of a swiveling axis and how they are influenced by thermal changes. The thermal influence on the error motions of a rotary axis is quantitatively parameterized by geometric errors that vary with time.