The Application of High Accuracy Sensors on Precision Machine Tool Accuracy Improvement
Date Issued
2015
Date
2015
Author(s)
Yang, Hao-Wei
Abstract
This research develop high accuracy multiple degrees of freedom sensors, including high resolution laser straightness measurement system and autocollimator. The sensors can detect straightness, pitch, yaw, and roll errors of the linear guideways and linear stage. By using laser expander and drift compensated system, the laser drift caused by the temperature and pressure can be reduced. The application of the digital filter can decrease the noise of the signal and improve the stability of the systems. According to the Abbe principle, the angular errors will be enlarged by the Abbe offset. The Abbe error is considered to be the major cause of volumetric error of machine tool. In the measurement system, we use the autocollimator and roll sensor to measure errors during the movement of machine tool and compensate the three angular errors immediately. Derive the volumetric error model of three-axis machine tool by homogeneous transformation matrix and compare to the volumetric error model which follow the Abbe principle. Experiment shows that the volumetric error model we proposed can significantly improve the accuracy of machine tool. Furthermore we apply the Bryan principle, the measurement axis of the straightness sensor and cutting axis cannot be coaxial. By using angular errors and Bryan offset, we can calculate the straightness error at any point in the space. Using the model we proposed to analyze and set up the error budget of a particular precision machine tool developed by the Industrial Technology Research Institute (ITRI). By using the error budget method, we can find the most cost-effective way to allocate the limit value of each geometric error of 3-axis as the guideline of installation in order to control the total volumetric errors of the machine tool. In order to achieve the target accuracy, the geometric errors of the linear stage must be decreased. The assembly error will affect the accuracy of linear guideway. The parallelism of two linear guideway will cause the pitch, yaw, and roll error. This research provides the method to adjust the linear guideway which can significantly reduce errors of the stage and achieve the target accuracy.
Subjects
volumetric error
Abbe error
Bryan error
machine tool
three DOF sensors
Type
thesis
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