SELECTION OF THE RATIONAL DESIGN OF THE PENTAPOD MACHINE TOOL END EFFECTOR BY CRITERION OF REDUCED STIFFNESS
Journal Title: Вісник Кременчуцького національного університету імені Михайла Остроградського - Year 2018, Vol 1, Issue 112
Abstract
Purpose. The purpose of the work is to determine the rational design and geometric parameters of the end effector of pentapod machine tool by the magnitude and nature of the change brought to the zone of processing of forward stiffness. Methodology. The general matrix of stiffness of a pentapod parallel kinematic machine is determined by considering its links working on tension-compression and torsion, as translational and torsional springs of known stiffness. From the obtained matrix, we determine the matrix of translational stiffness reduced to the processing zone, which makes it possible to estimate the nature of the elastic displacements of the tool under the influence of the technological load. Results. The basic geometric parameters are established in the work and five variants of the design of the end effector of pentapod machine tool are proposed. The basic geometric parameters are established in the work and five variants of the design of the end effector of the pentapod machine tool are proposed. Constructed dependences of the value of reduced stiffness on the change of coordinates of the pole of the end effector in the range from -0.20 m to 0.20 m on the X, Y, and Z axes in the horizontal and vertical arrangement of the end effector and the rotation angles in the space, and three-dimensional graphs were constructed for reduced translational stiffness in the directions of coordinate axes at z = 0.30 m. Obtained dependencies showed that the largest difference of stiffness for different layers of the end effector is observed along the X axis, and the best option is the arrangement of 3-2. Also, dependencies of the influence of the geometric dimensions of the end effector on the magnitude of the reduced stiffness zone were obtained, therefore, in order to increase the stiffness, it is necessary to increase the radius of the end effector joint, so that the first joint has minimal distance to the tool, as well as increase the overall length end effector. Originality. For the first time, the dependence of the influence of the end effector joints arrangement on the reduced stiffness was obtained, and the recommendations regarding the rational choice of the geometric parameters of the end effector were proposed. Practical value. The work makes it possible to determine the design and rational parameters of the end effector according to the specification at the design stage for parallel kinematic multi-axis machine tools.
Authors and Affiliations
О. Shelepko, А. Kyrychenko
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