Advanced Materials Research Online: 2008-07-7 ISSN: 662-8985, Vols. 53-54, pp 65-68 doi:0.4028/www.scientific.net/amr.53-54.65 2008 Trans Tech Publications, Switzerland Internal Magnetic Abrasive Particles Surface Finishing Based on Permanent Magnetic Field H. L. Chen, a, S. C. Yang, b, J. M. Wang, 2, c, W. H. Li and G. Y. Xiong 3 College of Mechanical Engineering, Taiyuan University of Technology, No.79, Yingze West Street, Taiyuan. 030024, P. R. China 2 Taiyuan University of Science and Technology 3 College of Electrical & Power Engineering, Taiyuan University of Technology, No.38, Waliu road, Taiyuan. 030024, P. R. China a chen-hl@263.net, b yangsc@tyut.edu.cn, c wjmhdb@63.com Keywords: Magnetic abrasive particle, Finishing, Magnetic pole, Surface roughness Abstract. To internal magnetic abrasive particles surface finishing, the motion of magnetic abrasive particles was influenced not only by the intensity of magnetic induction, but also by the internal diameter, and the magnetic inductive capacity was also an important factor that influences finishing quality. In this paper, under the same experimental conditions, electromagnetic field and permanent magnetic field were respectively used to magnetic abrasive particles surface finishing on thin stainless steel bush and 45 steel bush, new thoughts on inserted permanent magnetic pole and butted permanent magnetic pole were pointed out. The finishing quality of two kinds of work pieces under three different magnetic poles was compared. The results have shown that permanent magnetic pole could decrease the surface roughness Ra of work piece from.6μm to 0.2μm, which could solve the puzzles encountered in internal magnetic abrasive particles surface finishing on magnetic inductive work piece and had good promising application value. Introduction The finishing on internal surfaces are more difficult than that on external surfaces [], and the finishing on smaller internal surfaces are much more difficult than that on larger size ones. Due to the self-adaptive characteristics of magnetic surface finishing, i.e., the abrasive tool is composed of numerous abrasive particles, and can be regarded as flexible magnetic brush, which varies with the shape of work piece. It can also be loaded into the vessel with micro aperture or tiny hole, which has been proved to be a new process in internal surface finishing. Because the lapping pressure was produced by magnetic field, under the same machining conditions, the finishing quality would be different due to the magnetic inductive property of work piece. In this paper, the internal magnetic abrasive surface finishing process for small size work piece was specially studied, and permanent magnetic pole was further discussed to realize internal magnetic abrasive surface finishing on magnetic inductive work piece. Experimental Conditions Workpiece. Stainless steel bush, Wall thickness.5 mm, diameterφ40mm, length 00mm. 45 steel bush: wall thickness 4mm, the other sizes were the same as those of stainless steel bush. Process Parameters. Workpiece revolution speed v=80 m/min, axial vibration frequency f=3 Hz, axial amplitude a=5 mm, magnetic inductive intensity B=(0.3-0.7) T, machining clearance Δ=(2-5) mm. Magnetic Abrasive Particles. Material type Al 2 O 3 +Fe, particle diameter 25μm, fill amount (0-30) g. 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, www.ttp.net. (ID: 30.203.36.75, Pennsylvania State University, University Park, USA-09/04/6,0:25:09)
66 Surface Finishing Technology and Surface Engineering Experimental Procedures and Result Analysis Finishing by Electromagnetic Pole. Currently electromagnetic method shown in Fig. was generally applied in most internal surface magnetic finishing. Magnetic poles were arranged into some angle (usually rectangles) to produce asymmetric uneven magnetic field in machining area, thus realizing internal magnetic surface finishing [2, 3]. The experimental finishing results on stainless steel bush and 45 steel bush shows that the surface roughness of stainless steel has reduced from.58 μm to 0.8 μm. While excessive magnetic flux lines on 45 steel bush, it would accumulate on steel wall to form magnetism shield, so less magnetic flux in bush produced weaker magnetic intensity, finally resulted in smaller lapping pressure, and the finishing quality was very poor. So, such type was mainly applied in finishing work piece of nonmagnetic inductive materials. 2 -workpiece 2-magnetic abrasive particle Fig. Diagram of internal magnetic abrasive surface finishing process by electromagnetic Finishing by Permanent Magnetic Pole. Permanent magnetic pole on finishing small size bush could combine magnetic source and magnetic pole together, its structure was simple and easy for machining. Inserted Magnetic Pole. The inserted magnetic pole was shown in Fig. 2. A number of through holes with center distance 2 mm were machined on nylon bar along the axial direction with reciprocally-crossed angles. Then the permanent magnetic bar with diameter 8mm and height 28 mm was axially magnetized to form inserted magnetic pole. Both above work pieces were lapped. The experimental results in Fig. 3 displayed obviously good finishing quality. However, the sizes of permanent magnetic bar were restricted by the small hole diameter. To stainless steel bush, the magnetic field was relatively weak and the lapping pressure was smaller, thus the according surface roughness after finishing was a little larger than that by electromagnetic mode. 2 - permanent magnetic bar 2- nylon bar Fig. 2 Diagram of inserted permanent magnetic pole
Advanced Materials Research Vols. 53-54 67 Ra/μm.8.6.4 stainless steel 45.2 0.8 0.6 0.4 0.2 0 0 2 4 6 8 T/min Fig. 3 Relationship between surface roughness and finishing time Butted Magnetic Pole. The butted magnetic pole shown in Fig.4 was developed to make up for the defaults in inserted magnetic pole. The permanent magnetic bar was axially charged with magnetism, its diameter is 20 mm, the length is 0 mm. The butted magnetic inductive plate is 45 steel with diameter 26 mm and length 8 mm, counter bores with depth.5 mm and diameter 20 mm were axially machined on both ends, as shown in Fig. 4. To prevent the accumulation of magnetic particles between poles, butted magnetic poles were formed by nonmagnetic filling between two permanent magnetic poles. After finishing on two work pieces, both experimental results shown in Fig. 5 displayed good finishing quality. The variation of surface roughness with finishing time was more than that by inserted magnetic pole, and the surface roughness after finishing was less than those by inserted magnetic pole and electromagnetic pole. The distribution lies of magnetic flux and magnetic density were shown in Fig. 6, from which we could know that the magnetic flux lines and density on 45 steel bush were more than those on stainless steel bush. Therefore, the more lapping pressure produced better surface quality than that on stainless steel bush. The best advantage of magnetic pole not only ensured enough magnetic inductive intensity to meet the demands of uneven magnetic field, but also realized the aggregation of magnetic flux lines. Moreover, such compact pole was easy to make and could save materials. 2 3 4 5 -workpiece 2- magnetic inductive plate 3- nonmagnetic filling 4- magnetic abrasive particles 5- permanent magnetic bar Fig. 4 Diagram of finishing process by butted permanent magnetic pole
68 Surface Finishing Technology and Surface Engineering Ra/μm 2.5 0.5 stainless steel 45 0 0 2 4 6 8 T/min Fig. 5 Relationship between surface roughness and finishing time (a) Stainless steel bush (b) 45 steel bush Fig. 6 Distribution lines of magnetic flux and magnetic density Conclusions Permanent magnetic pole has been used to internal surface lapping, which not only makes machining mechanism structure more simple and convenient, but also could save a lot of cost. Especially such method could be used to solve the puzzles in internal magnetic surface finishing on magnetic work pieces and burring on axial holes. References [] S. C. Yang, M. Z. Wang and Y. X. Zhang: The Surface Quality and Finishing Technology. (China Machine Press. 2000) [2] Y. Y. Guo, Y. X. Zhang and S. C. Yang: Chinese Journal of Mechanical Engineering. Vol. 8(6) (997), p.23 [3] T. Shinmura, H. Yamaguchi: J. of JSME International Journal. Series C, Vol.38 (4) (995), p.798
Surface Finishing Technology and Surface Engineering 0.4028/www.scientific.net/AMR.53-54 Internal Magnetic Abrasive Particles Surface Finishing Based on Permanent Magnetic Field 0.4028/www.scientific.net/AMR.53-54.65