Geometrical instruments – Distance measuring – Error compensation
Utility Patent
1999-03-29
2001-01-02
Gutierrez, Diego (Department: 2859)
Geometrical instruments
Distance measuring
Error compensation
C033S503000
Utility Patent
active
06167634
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a measurement and compensation system, and more particularly to a measurement and compensation system for thermal errors in a guideway and a spindle of a machine tool.
Recently, development of efficient techniques for performance verification of the multiaxis machine tools has been considered as an important task for accuracy enhancement and quality assurance for users and manufactures of machine tools and coordinate measuring machines. In order to perform precise position control and to promote accuracy of the multiaxis machine tools, the development of efficient techniques is directed to compensation of the three dimensional volumetric errors, since it is essential to measure and analyze each error component and to compensate the three-dimensional volumetric errors.
The static errors include geometric errors, kinematic errors, and thermal errors, etc. and dynamic errors include errors due to servo gain mismatch and dynamic characteristics. Considering the thermal errors, the thermal errors are very important because the thermal errors account for 50 percent or more of all the errors. The thermal errors are produced by inward heat and outward heat in machine tools. The inward heat includes heat between two operating members and heat of motors and heat due to friction etc., and the outward heat includes heat due to environmental temperature and heat due to a direct ray of light etc. The heat expands the members of the machine tool and causes the machine tool to be deformed. Therefore, the heat has an important influence on the processing accuracy of the machine tool. However, in practice, it is very difficult to compensate the thermal errors during the operation of the machine tool.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a measurement and compensation system for thermal errors in a machine tool to compensate thermal errors generated in the machine tool.
It is another object of the present invention to provide a measurement and compensation system for thermal errors in a machine tool wherein the system is additionally mounted to the machine tool as a module.
According to the present invention, these objects are achieved. There is provided a measurement and compensation system for thermal errors in a machine tool comprising, a data bank for storing in operating conditions of a guideway and a spindle of the machine tool, and values of all coefficients of a thermal error modeling equation which governs a relation between thermal errors and temperatures of the guideway and the spindle; a plurality of sensors fixed to a plurality of regions of the guideway and the spindle of the machine tool to measure temperatures of the regions of the guideway and the spindle; an analog to digital converter for converting analog signals of the sensors to digital signal; an encoder provided near the guideway to measure positional coordinates of a bed which moves rectlinearly by means of rotation of the guideway; a counter operatively connected to said encoder for detecting the positional coordinates of the bed by counting pulse signals of said encoder; an operating part for receiving outputs of said analog to digital converter and said counter and for selecting from said data bank the values of all the coefficients of the thermal error modeling equation corresponding to the temperatures measured by said sensors and for calculating the thermal errors; a digital input/output part operatively connected to said operating part for converting digital data of the thermal errors calculated by said operating part to digital signals; a controller for receiving the digital signals of the thermal errors of the guideway and the spindle outputted from said digital input/output part and for receiving the positional coordinates of the bed outputted from said encoder and for giving order to compensate the positional coordinates of the bed by the thermal errors calculated by said operating part; and wherein said data bank, said analog to digital converter, said counter, said operation part, and said digital input/output part are formed by a module.
The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure.
For a better understanding of the invention, its operating advantages and specific objects attained by its uses, reference is made to the accompanying drawings and descriptive matter in which the preferred embodiments of the invention are illustrated.
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Lee Suk Won
Pahk Heui Jae
Fernandez Maria
Gutierrez Diego
Lowe Hauptman Gopstein Gilman & Berner
Snu Precision Co., Ltd.
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