Experimental Study On Improving The Polishing Quality And Efficiency Of Internal Surface Of Bending Pipe

With the high speed development of national defense industry, food, medical and chemical machinery, space bending pipe has been widely used in engine, gas transportation and fluid transportation. In the process of pressing and bending, the surface defects such as stripes, folds and pits will occur on the inner surface of bending pipe. It caused grease blockage and air pressure fluctuation, even lead to the engine work instability and the work efficiency reduced. It is difficult to polish the inner surface of bending pipe when the traditional method is used. Therefore, some scholars proposed that the method of magnetic abrasive finishing combined with six degrees of freedom mechanical arm could be used to polish the inner surface of bending pipe, and better surface quality was achieved. But the six degree of freedom mechanical arm is expensive and most small and medium sized enterprises can not afford to the high cost. It limits the wide application of magnetic abrasive finishing in the factory. Therefore, a handheld bending pipe polishing machine based on the magnetic abrasive polishing is developed to replace the six degree of freedom mechanical arm. The handheld bending pipe polishing machine can reduce the processing cost, and promote the application of magnetic abrasive finishing method in the factory.In this paper, the mechanical properties of the magnetic abrasive particles and the material removal mechanism in the process of magnetic abrasive finishing are studied.Several factors affecting the grinding efficiency and grinding quality are obtained,among them the most important factor is the effect of grinding pressure. Through the analysis of the materials removal mechanism, the material removal in the process of grinding is the result of combined action of the mechanical and chemical interaction.In this paper, the advantages and disadvantages of two alternative designs for bending pipe polishing machine are analyzed, and the program of bending pipe polishing machine based on guide device is determined. On the basis of consulting a large number of domestic and foreign documents, the inner surface polishing machine for bending pipe is developed. The inner surface polishing machine for bending pipe is composed of the main body of the polishing machine, the driving part, the transmission part and the polishing part. The Maxwell Ansoft software is used to simulate the influence of the edge tilt angle of pole head and whether the pole head is slotted on magnetic induction intensity in the polishing part, and the conclusion that the magnetic induction intensity in processing region is largest when the angle of the edge is 60 degrees is obtained. The performance of bending pipe polishing machineand the processing quality of magnetic abrasive finishing are studied, research shows simply adding magnetic abrasive particles into the bending pipe can realize the polishing purpose, but machining efficiency and machining quality are not ideal.From the mathematical model of the grinding process, it can be known that increase the grinding pressure is an effective method to improve the grinding efficiency. So, in order to improve the machining efficiency, spherical auxiliary magnetic poles with different volume were input bending pipe. However, with the increase of the spherical magnet volume, mutual abrasion phenomenon between spherical magnet and inner surface of bending pipe will appear, so cylindrical auxiliary magnetic pole is used to solve this problem. In the process of MAF,improper selection of the volume of cylindrical magnet will result in path interference problem, cylindrical magnet obtained by cutting the spherical magnet with a cylindrical surface can avoid path interference problem. The finite element analysis and experiment result shows that compared with the spherical magnet, when cylindrical magnet as the auxiliary magnet, the processing efficiency is higher, the greater grinding pressure can be obtained and more dense and uniform finished surface obtained. Besides, the increased of processing region extend grinding area.Moreover, the lapping trace of MAPs is more complicated and intensive, so the processing time is shortened and the processing efficiency is improved.