Evaluation for the Relationship between Positioning Accuracy of Machine Tools and ISO 230 Testing Result Using an Auto-Tracking Laser Interferometer

Abstract

For three-axis machine tools, positioning accuracy and repeatability can be tested according to ISO 230-2 and ISO 230-6. Traditionally, the testing is performed by means of a laser interferometer in which it is time consuming with measurement uncertainty becoming large and then measurement time increased. For shortening the measurement time to avoid large measurement uncertainties and increasing assembly productivity, spatial measurement instruments, such as auto-tracking laser interferometers (ATLIs), are necessary. Measurement uncertainty of the LaserTRACER used in this evaluation study is (0.2 μm + 0.3 μm/m × L) which is smaller than any uncertainty of ATLIs such as laser trackers. LaserTRACER is applied in this study for positioning accuracy and repeatability testing of three axis machine tools according to ISO 230-2 and ISO 230-6. Because the relationship between coordinate systems of the machine tool and the ATLI was unknown in the beginning, it is proposed at the first step here to figure out through an implemented locating means the coordinate position of the ATLI on the coordinate system of the machine tool, through which step we call it the coalescence of the two coordinate systems. For a LaserTRACER, such coordinate system coalescence is carried out through the machine tool running six independent points in 3D space.