[机械模具数控自动化专业毕业设计外文文献及翻译]【期刊】对于数控车床尾座主体的特性分析及其优化设计-外文文献

Advanced Materials Research Vol. 1037 (2014) pp 41-44 Submitted: 2014-06-11 (2014) Trans Tech Publications, Switzerland Accepted: 2014-08-07 doi:10.4028//AMR.1037.41 Online: 2014-10-27 Characteristic Analysis and Optimization for The Tailstock Body of The NC Lathe LU Mo-Wu, Li Ming-Jie JIANGSU,HUBEI,CHINA 570454645, Keywords: tailstock body; statics analysis; modal analysis; topology optimization; Workbench; Abstract. The characteristics of the NC Lathe tailstock has great influence on the machining accuracy of NC machine tools. Solidworks software is used to establish the tailstock body entity model, then import it into the Workbench software for finite element analysis and conclude its dynamic and statics characteristics. According to the result of the analysis on the topology optimization. Guarantee after optimization, the tailstock body not only can satisfy the requirement of machine tool, the quality can also be reduced by 5%. In saving material at the same time also can reduce the motion inertia, improve the machining accuracy. INTRODUCTION The tailstock is an important part of the CNC lathe, it plays a role in positioning and clamping workpiece. Its static and dynamic characteristics have a direct impact on the machining accuracy and stability. When heavy duty NC lathe machining different parts, tailstock need reciprocating movement to complete the task of clamping, positioning workpiece. So this requires the tailstock weight is lighter, increase the flexibility of the organization as far as possible. In this paper, HTC100 CNC lathe tailstock box as an example, by establishing an accurate physical model, using ANSYS Workbench software to finish finite element analysis and its topology optimization then obtain a better structure. Provide a feasible reference for the reasonable design of the tailstock body. FINITE ELEMENT MODEL Figure 1 (a) is about HTC100 CNC lathe tailstock body structure, it assembly formed by the upper and lower cabinet as FIG 1 (b), (c) shown in. The bottom of tailstock is fixed on the bed through the slide rail and bolt. Figure 1 (a) the tailstock box model (b) the upper box model (c) the lower box model HTC100 horizontal CNC lathe tailstock is casted by the HT300. The modulus of HT300 is 1.43E11Pa, Poisson ratio is 0.27 and density is 7340Kg/m3. Meshing is an important part of the finite element analysis. This paper chooses Patch in Conforming method which belongs to the Tetrahedrons method to mesh the tailstock box model. The reasons why this method is selected are that it is fast and applicable to the complex geometry; All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of Trans Tech Publications, . (ID: 12, Univ of Massachusetts Library, Amherst, USA-11/07/15,21:55:17) 42 Development of Applied Engineering Sciences Approximate size in the key areas can be refined. The finite element model is obtained after mesh is shown in Figure 2, The number of nodes model is 55973 and the total number of unit is 32024. Figure 2 The finite element model of box. Figure 3 The boundary conditions of box It must be applied boundary conditions on the box in the ANSYS before analyzing statics and dynamics of the tailstock box, including the force, torque and support surface. The tailstock body internal stress mainly comes from gravity of parts. Besides the gravity of the internal parts, the tailstock box is also got the cutting force and moment during the machining process. Taking the shaft machining as an example, According to the empirical data, the tailstock clamping force is 5.28KN, the maximum cutting force is 60KN. The main cutting force is 53.4KN, back force is 18.6KN and feeding force is 20.4KN. After stress analysis, the force and torque come from tip is got as follows: Fx =560N, Fy =1572350N, Fz =15120N, M =8811N.m. Apply these forces and moments to each surface of box, The tailstock body fixed on the bed, so the bottom of the box body is got by fixed constraint. Boundary conditions are applied in the Workbench as shown in Figure 3. FINITE ELEMENT ANALYSIS The result of the static analysis has an important reference value to optimize the structure of the box body. Analysis of static images as shown in Figure 4, the maximum displacement of the box body is 1.23E-004m, the maximum stress is 4.44E+007Pa. The results show that the maximum displacement of box is small, it can satisfy the precision demand. The ultimate stress of HT300 is 300MPa. The maximum stress of tailstock box is far less than the limited material stress, Box rigidity meets the requirements, thus it may carry on further optimization. During the process, machine tools generate periodic variational excited force by the interaction of noise and vibration. Its easy to cause the resonance when the frequency of excited force is the same or integer with the natural frequency of structure. It will reduce the machining precision and stability of machine tool. So it is necessary to carry out the modal analysis of the tailstock box. Figure 4 The displacement and stress nephogram of tailstock body Advanced Materials Research Vol. 1037 43 After modal analysis of box in the ANSYS, the first six-order modal is concluded as shown in table I. The maximal speed of spindle of HTC100 CNC lathe is 200rpm and the frequency is 3.33Hz. It can be seen that the excitation frequency of the tailstock is far less than itself first six-order frequency from table 1. Table 1. The low-order mode of box UnitHz Pattern 1-order 2-order 3-order 4-order 5-order 6-order Frequency 272.27 283.95 462.53 636.54 747.78 806.67 TOPOLOGY OPTIMIZATION Topology optimization is refers to find the best solution of structural materials used to make the target volume (overall stiffness, natural frequency etc.) stable under given constraint condition. Using Shape Optimization function in Workbench to finish the tailstock box topology optimization. The optimization goal is set to 5 percent, then solve it, optimization results as shown in Figure 5. Figure 5 The topology optimization nephogram Figure 6 The geometry structure after optimization As the red resectable area is irregular, the complexity of technology and stress distribution must be considered in the actual processing. So it is impossible to remove all red area. Cut off the red area in regular geometry in Solidworks, then quality reduces 1250.4Kg. The geometric structure after optimization as shown in Figure 6. Make the finite element analysis on the optimization scheme and the displacement, stress nephogram as shown in Figure 7. The maximum displacement of box is 1.19E-004m and the maximum stress is 4.57E+007Pa after optimization. Modal analysis on the box body after structure optimized is carried out and get the low order mode as shown in table 2. Figure7 The displacement and the stress nephogram after optimization Make statics and dynamics analysis on the optimized box structure, it can be seen the tailstock body still meet the stiffness requirement and machining accuracy after optimization. Moreover, the quality reduced, the movement inertia enclosure and the control performance improved. 44 Development of Applied Engineering Sciences Table 2. The low-order mode of box after optimization UnitHz Pattern 1-order 2-order 3-order 4-order 5-order 6-order Frequency 278.98 290.52 471.10 653.54 743.03 781.12 CONCLUSION Doing topological optimization to the tailstock box in Workbench, the maximum displacement, maximum stress and the low frequency basically unchanged after optimization design of the tailstock box. It meets the design requirements and the quality is reduced by 5%.It makes the tailstock movement more flexible. Using finite element software to analyze the products can save the cost of manufacturing prototype and testing. Getting the main properties of the product in the software, it could provide optimized structure and size. REFERENCES 1 He Chong-yu, Yin Zhi-hong. A