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A new measurement system to determine stiffness distribution in machine tool workspace

Pawełko Piotr, Jastrzębski Daniel, Parus Arkadiusz, Jastrzębska Joanna

Archives of Civil and Mechanical Engineering

2021

Vol. 21, no. 2

157--168

This paper presents an innovative system determining machine tool quasi-static stiffness in machining space, so-called Stiffness Workspace System (SWS). The system allows for the assessment of the accuracy of a machine which has become a vital aspect over past years for machine tool manufacturers and users. Since machine tools static stiffness is one of the main criteria using to evaluate the machines' quality, it is crucial to highlight the relevance of experimental and analytical stiffness determination methods. Therefore, the proposed method is applied to estimate the spatial variation of static stiffness in the machine tool workspace. This paper describes the SWS system-its design, working principle, mounting conditions and signal processing. The major advantage of the system is the capability to apply forces of controlled magnitude and orientation as well as simultaneously measure the resulting displacements. The obtained results give possibility to estimate and evaluate static stiffness coefficients depending on the position and direction under loaded conditions. The results confirm the validity of the analyses of spatial stiffness distribution in the machine workspace.

Static condensation in modeling roller guides with preload

Dunaj Paweł, Berczyński Stefan, Pawełko Piotr, Grządziel Zenon, Chodźko Marcin

Archives of Civil and Mechanical Engineering

2019

Vol. 19, no. 4

1072--1082

This article presents the methodology for modeling the stiffness of a machine tool load-bearing system using the finite element method. A new, simplified model of stiffness of the linear guide with a preload based on equivalent contact model was proposed. An equivalent contract model was developed where the ball was replaced with four rod elements of equivalent stiffness, interconnecting the opposite ends of the face of cuboidal finite ele- ments. To shorten the computation time and facilitate modeling reduction and substructur-ing methods was used. The accuracy of the proposed model was compared with experimental results. In addition, the computation times were evaluated by comparing the simplified model with the full model and other equivalent models. Then, the model was used to determine the stiffness of the machine load-bearing system on the example of a machining table using the aforementioned methods and the obtained results were com-pared in terms of accuracy (less than 1% difference in maximum displacement value) and computation time with the classic approach (up to 97% in time reduction). This paper demonstrated the validity of the proposed model, allowing accurate and fast determination of the stiffness of machine tool load-bearing system.