Geometric- and force-induced errors compensation and uncertainty analysis of rotary axis in 5-axis ultra-precision machine tool

Abstract Aspherical or free-form optical surface machining using an ultra-precision machine tool is a common and effective method in precision optics manufacturing. However, this method sometimes causes waviness due to the machine’s motion in mid-spatial frequency (MSF) form deviations. This waviness lowers the quality of the optical surface. To address this problem, we use the waviness of the axial displacement of the ultra-precision machine tool. The waviness is obtained by a non-contact on-machine metrology (OMM) system that measures an optical flat as a correction reference curve, which is used to correct the surface of the workpiece to reduce the effect of waviness in advance. The OMM system consists of a displacement probe and a machine tool axis position capture device. The probe system uses a confocal chromatic probe on an ultra-precision machine tool to evaluate the form deviation of the workpiece with 1 nm resolution. The axis position capture system uses a signal branch circuit of linear scale on each axis from the ultra-precision machine tool. The OMM system is tested in terms of accuracy and repeatability. In comparison to the results of the shaper cutting of an oxygen-free copper (OFC) workpiece with feed-forward correction, we were able to reduce the profile error from 125.3 nm to 42.1 nm in p-v (peak to valley) and eventually also reduced the waviness.

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Quadrant Protrusion Measurement of Ultra-Precision Machine Tool by Real-Time Position Capturing Method

Materials Science Forum ◽

10.4028/www.scientific.net/msf.874.531 ◽

2016 ◽

Vol 874 ◽

pp. 531-536 ◽

Cited By ~ 1

Author(s):

Hao Duan ◽

Takuya Hosobata ◽

Masahiro Takeda ◽

Shinya MORITA ◽

Yutaka Yamagata

Keyword(s):

Machine Tool ◽

Real Time ◽

Data Storage ◽

Optical Element ◽

Linear Interpolation ◽

Precision Machine ◽

Control Code ◽

Ultra Precision ◽

Time Position ◽

Circular Interpolation

This paper describes a development of a real-time position capturing method in which branched encoder signals are recorded in external data storage, to evaluate motion trajectories of the XYZ table on ultra-precision machine tool. The method allows the capturing with minimal modification to the machine: without any additional sensors. In the previous study we generated a non-axisymmetric aspherical optical element by XZC-axis simultaneous numerical controlled ultra-precision turning process with 2 μm form deviation, the reason of form accuracy degradation wasn’t identified. Using the developed system, motion accuracy of ultra-precision machine tool is confirmed. The machine tool moves along circular trajectory in three coordinate planes (XY, YZ and ZX) respectively. The rotation direction of circle is set clock wise and counter clock wise. The circle processing interpolation command by linear interpolation control code and circular interpolation control code. The results showed the effectiveness of the proposed method for performance evaluations of machine tools, by revealing the influence of trajectory parameters on the magnitudes of quadrant protrusions.

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