Laser R-Test
 
 

To measure the motion accuracy of rotary axes in a five-axis machine tool, we have studied the measuring instrument called the R-Test. As a rotary axis rotates, two linear axes move along a circular path, and the R-Test measures the 3D displacement of the rotary axis with respect to the linear axes. We have developed a software to analyze the R-Test results, which is commercially available from Fukuda Corp. ("FKD System").

Typically, the R-Test uses a set of three tactile linear displacement sensors (see Fig. 2). Prof. Wen-Yuh Jywe and his group in National Taiwan University (National Formosa University in Taiwan during the collaboration project) have developed the Laser R-Test. It measures a sphere's 3D displacement in a non-contact manner, by using the refraction of the laser beam through a glass sphere. It is commercially available.

In this collaboration project with Prof. Wen-Yuh Jywe's group, we have studied the measurement performance of the Laser R-Test. A tactile linear displacement sensor typically has a spring inside to push its probe to a target. Its dynamics may limit the measurement bandwidth. Furthermore, the friction with the contact of the probe surface with a target can potentially influence the measurement accuracy. Therefore, non-contact Laser R-Test can potentially exhibit better measurement accuracy than tactile R-Tests particularly in dynamic tests. Their actual measurement performance was experimentally compared in the tests described in ISO 10791-6:2014.

This project was under the collaboration with Prof. Wen-Yuh Jywe's group in National Taiwan University (National Formosa University during the collaboration project)
(Koki Onodera, Soichi Ibaraki, March 2021) (written in July 2023)

>> Publications: JE23, CJ23, CJ14, CJ7

 
 

Figure 1: Laser R-Test. As the rotary table (C-axis) rotates, the spindle-side moves along a circular path, during which the sphere 3D displacement is continuously measured.

Figure 2: Conventional R-Test with three tactile linear displacement sensors. The same test as Fig. 1 was conducted, and its measurement performance was compared.

Figure 3: This test, described in ISO 10791-6:2014, does not require a special, designated measuring instrument; it can be done by using a sphere and a linear displacement sesor. For higher accuracy measurement, a laser displacement sensor, SI-F10 by Keyence, was used. When only a single sensor is available, for the 3D measurement, a similar test must be conducted with three different sensor directions.
 
 
 
 
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