Effect of Ball Screw linear expansion of linear axes on the movement of rotary axes and workpiece geometric accuracy in five-axis CNC milling machine with rotational head and RTCP active option
Subject Areas : Dynamic Analysis
Amir
Alinaghizadeh
1
(Faculty Member-Lecturer at Islamic azad university of semnan branch- Mechanical Engineering Department (Manufacturing & Production))
Meysam
Khaki
2
(Master Science of Mechanical Engineering-Manufacturing, Ministry of Education, Tehran, Iran)
Keywords: RTCP, Ball Screw, Five-axis CNC milling machines, geometric accuracy, linear expansion,
Abstract :
During machining a portion of the heat generated by operation activities edges of cutting tool relative to the workpiece is transferred to machine tool, and in addition, the friction generated in continuous motion of Ball Screw and the Nut that Due to shift of axis machine is created, causing the expansion of the Ball Screw size will be. Because of the length of the high ratio of length to diameter, expansion of the length of Ball Screw to be important. Because after every movement applied to in the NC, according to the size difference between the previous program and the current line, in addition to the original displacement, had done an additional displacement due to the expansion of the Ball Screw. Machines CNC five-axis, in addition to the direct impact of linear expansion length of Ball Screw linear axes for the accuracy of the workpiece geometry, the indirect effect are also considering option RTCP (Rotation Tool Center Point), to move the axis rotary is shown. The RTCP active, the center of cutting tool is fixed in space instead of, the center of the rotary axes are moving. In this case, to compensate for displacement of cutting tool, In effect movement the rotary axes, linear axes will be moved. In this paper, directly or indirectly effect of Ball Screw linear expansion on the workpiece geometric accuracy studied using analytical-mathematical And the results can be compared with the adaptive control as five-axis CNC machines used in the paper.
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