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|Title:||Modeling, Parameter Estimation and Compensation of Quasistatic Errors in Multi-Axis CNC Machining Centers|
|Author(s):||Kiridena, Vijitha Senaka|
|Doctoral Committee Chair(s):||Ferreira, Placid M.|
|Department / Program:||Mechancial Engineering|
|Degree Granting Institution:||University of Illinois at Urbana-Champaign|
|Abstract:||Dimensional accuracy is often the single most critical criterion that can be used to evaluate the quality of machined parts. Increasing demand for highly accurate and inexpensive mechanical parts has created a critical need for developing economical and efficient processes for their production.
Experimental evidence indicates that nearly seventy percent of the errors attributable to the machine tool are quasistatic errors. Attempting to control the quasistatic effects by improving rigidity of the machine tool and maintaining a constant thermal state during operation increases the initial, operational and maintenance costs. The overall objective of this thesis is to develop a methodology to increase the attainable accuracy of "production-class" multi-axis CNC machining centers by compensating quasistatic effects.
The objective of this thesis is achieved through several steps. First, a general quasistatic error model for three-axis CNC machining centers is developed using rigid body kinematics. This model compiles the effects of inaccuracies in the geometry and motion of machine members on its volumetric accuracy in its work space. For the general quasistatic error model to be used in a practical compensation scheme, its parameters need to be updated quickly and accommodated easily within the machine's work cycle. This is made possible by developing a method to identify few strategically located measurement points in the work space sufficient for robustly estimating the model parameters. Then efficient, and accurate computational strategies are developed for three-axis machining centers to introduce compensations using estimated quasistatic errors which produces the anticipated higher degree of accuracy. The modeling, estimation and compensation techniques together form a comprehensive methodology to track and compensate quasistatic errors for three axis machining centers.
As the first step towards extending this new methodology to five axis machining centers, positional error models are developed to investigate the effects of the positioning errors of the joints on the position and orientation of the cutting tool. Also a mathematical basis of a suitable experimental procedure is investigated in this thesis to measure the error characteristics of the rotary joints in five axis machine tools.
Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1993.
|Date Available in IDEALS:||2014-12-17|
This item appears in the following Collection(s)
Dissertations and Theses - Mechanical Science and Engineering
Graduate Dissertations and Theses at Illinois
Graduate Theses and Dissertations at Illinois