混粉电火花加工机理及其应用研究
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摘要
混粉电火花加工技术不仅在精密模具和精密零件的制造中发挥着重要的作用,而且在工件材料的表面强化方面也有着良好的应用前景,因而,受到了各国电加工界的高度关注,是当前的研究热点之一。
目前,对混粉电火花加工工艺与机理的研究已经取得了很大的进展,已经知道,粉末的加入增大了极间间隙,能够使放电点分散均匀,使加工状态稳定,降低工件的表面粗糙度,改善工件的表面质量,并大大提高了精加工速度。但是,对于产生这些现象的原因和混粉工作液中的放电模型,目前的研究还没有给出一个完整、合理的解释。
本文在系统总结国内外大量文献资料的基础上,以实验研究与理论分析相结合的方式,对混粉电火花加工的机理和工艺特性进行了深入研究,丰富和完善了混粉电火花加工技术现有的理论成果。
首先,运用流光(流注)理论对混粉电火花加工极间介质击穿的微观过程进行了详细论述,并在此基础上研究了放电通道的位形,认为放电通道由一电极表面流经粉末颗粒到达另一电极表面而形成串连放电,且以单通道放电为主,而正极放电点面积的增大改变了正极表面的热量分布,确保了加工表面粗糙度的改善。同时,由于粉末的存在,使前后两次脉冲放电的放电点位置无相互依赖关系而随机出现,从而实现了放电点的良好分散。
其次,根据工艺过程对粉末材料多样性的要求,研究了硅、铝两种粉末材料的加工工艺效果,发现适当增大铝粉工作液的浓度,可以达到与硅粉工作液相近的表面粗糙度和较高的材料去除率。而通过改变铝粉工作液的浓度,研究了粉末浓度对加工工艺特性的影响,发现粉末浓度保持在一个适宜的范围内对于改善加工表面粗糙度和提高材料去除率均有积极意义。
本文的研究成果对混粉电火花的实际应用具有一定的指导意义,并为建立混粉电火花加工的专家系统提供了实验依据;同时,对混粉电火花加工的机理模型作了有益的探索。
PMD-EDM is attracting great attention in electrical machining field because of the important role in manufacturing of precise moulds & parts and hardening of part surface.In recent years, great progresses have been made in the research on it. It is known that the mix of powders widens discharge gap, disperses discharge points evenly, stabilizes discharge process, reduces SR, hardens surface material and increases MRR. However, little explication about the mentioned phenomena and the discharge principle has been given fully.For this reason, the mechanism and processing performances of powder-mixed EDM are studied by means of theoretical analysis combined with experimental research in this dissertation to improve the technology.Firstly, by means of the streamer theory from gas discharging field, the gap breakdown procedure of powder-mixed EDM is discussed, and the shape of the discharge channel is subsequently deduced. It is believed that the discharge channel connects the electrode couple via some certain particle and series-discharging is then conducted. And the single-channel discharge model is accepted rather than the multi channel discharge model according to the analyzed results. The bettering of the machined surface roughness is accounted for the over expansion of the plasma channel radius at the anode which causes a decrease in the local energy density at the anode surface. In addition, because the particles eliminates the dependence of the new discharge position on the last discharge position, the discharge point can be uniformly dispersed all over the machining area, which also accounts for the improvement of the machined surface integrity.Secondly, in order to meet various needs for different powder material, the service performances of silicon powder and aluminium powder are studied. It is found that compared to silicon powder, if a higher concentration of aluminium powder is set, the same degree of surface roughness and a higher MRR can be achieved. With the aluminium powder concentration changed, the effect of powder concentration on the process performance is also researched, and keeping the powder concentration within a proper range is found important to both the machined surface roughness and MRR.The conclusions are helpful to guide application and will be the experimental base for constructing expert system of PMD-EDM, and the work also accelerates research on PMD-EDM mechanism.
目前,对混粉电火花加工工艺与机理的研究已经取得了很大的进展,已经知道,粉末的加入增大了极间间隙,能够使放电点分散均匀,使加工状态稳定,降低工件的表面粗糙度,改善工件的表面质量,并大大提高了精加工速度。但是,对于产生这些现象的原因和混粉工作液中的放电模型,目前的研究还没有给出一个完整、合理的解释。
本文在系统总结国内外大量文献资料的基础上,以实验研究与理论分析相结合的方式,对混粉电火花加工的机理和工艺特性进行了深入研究,丰富和完善了混粉电火花加工技术现有的理论成果。
首先,运用流光(流注)理论对混粉电火花加工极间介质击穿的微观过程进行了详细论述,并在此基础上研究了放电通道的位形,认为放电通道由一电极表面流经粉末颗粒到达另一电极表面而形成串连放电,且以单通道放电为主,而正极放电点面积的增大改变了正极表面的热量分布,确保了加工表面粗糙度的改善。同时,由于粉末的存在,使前后两次脉冲放电的放电点位置无相互依赖关系而随机出现,从而实现了放电点的良好分散。
其次,根据工艺过程对粉末材料多样性的要求,研究了硅、铝两种粉末材料的加工工艺效果,发现适当增大铝粉工作液的浓度,可以达到与硅粉工作液相近的表面粗糙度和较高的材料去除率。而通过改变铝粉工作液的浓度,研究了粉末浓度对加工工艺特性的影响,发现粉末浓度保持在一个适宜的范围内对于改善加工表面粗糙度和提高材料去除率均有积极意义。
本文的研究成果对混粉电火花的实际应用具有一定的指导意义,并为建立混粉电火花加工的专家系统提供了实验依据;同时,对混粉电火花加工的机理模型作了有益的探索。
PMD-EDM is attracting great attention in electrical machining field because of the important role in manufacturing of precise moulds & parts and hardening of part surface.In recent years, great progresses have been made in the research on it. It is known that the mix of powders widens discharge gap, disperses discharge points evenly, stabilizes discharge process, reduces SR, hardens surface material and increases MRR. However, little explication about the mentioned phenomena and the discharge principle has been given fully.For this reason, the mechanism and processing performances of powder-mixed EDM are studied by means of theoretical analysis combined with experimental research in this dissertation to improve the technology.Firstly, by means of the streamer theory from gas discharging field, the gap breakdown procedure of powder-mixed EDM is discussed, and the shape of the discharge channel is subsequently deduced. It is believed that the discharge channel connects the electrode couple via some certain particle and series-discharging is then conducted. And the single-channel discharge model is accepted rather than the multi channel discharge model according to the analyzed results. The bettering of the machined surface roughness is accounted for the over expansion of the plasma channel radius at the anode which causes a decrease in the local energy density at the anode surface. In addition, because the particles eliminates the dependence of the new discharge position on the last discharge position, the discharge point can be uniformly dispersed all over the machining area, which also accounts for the improvement of the machined surface integrity.Secondly, in order to meet various needs for different powder material, the service performances of silicon powder and aluminium powder are studied. It is found that compared to silicon powder, if a higher concentration of aluminium powder is set, the same degree of surface roughness and a higher MRR can be achieved. With the aluminium powder concentration changed, the effect of powder concentration on the process performance is also researched, and keeping the powder concentration within a proper range is found important to both the machined surface roughness and MRR.The conclusions are helpful to guide application and will be the experimental base for constructing expert system of PMD-EDM, and the work also accelerates research on PMD-EDM mechanism.
引文
[1] 赵万生.先进电火花加工技术.北京:国防工业出版社,2003.
[2] 朱玲龙,杨连文,赵福令.混粉电火花加工工艺初探.电加工,1999(5):25-27
[3] K. H. Ho, S. T. Newman. State of the art electrical discharge machining(EDM). International Journal of Machine Tools & Manufacture, 2003, 43(10): 1287-1300
[4] Y. S. Wong, L. C. Lim, Iqbal Rahuman et al. Near-mirror-finish phenomenon in EDM using powder-mixed dielectric. Journal of Materials Processing Technology, 1998, 79: 30-40
[5] 徐小兵,毛利尚武.日本电火花加工技术的发展动态.电加工与模具,2003(1):1-3
[6] 吴敏镜.漫谈电火花加工的发展与展望.新技术新工艺,1999(5):13-15
[7] P. M. George, B. K. Raghunath, L. M. Manocha, Ashish M. Warrier. EDM machining of carbon-carbon composite—a Taguchi approach. Journal of Materials Processing Technology 2004,145(7):66-71
[8] D. T. Pham, S. S. Dimov, S. Bigot et al. Micro-EDM—recent developments and research issues. Journal of Materials Processing Technology, 2004, 149: 50-57
[9] 何广敏,赵万生,郭永丰等.混气电火花镜面加工的研究.制造技术与机床,2000(3):43-45
[10] A. Curodeau., M. Richard, L. Frohn-Willeneuve. Molds surface finishing with new EDM process in air with thermoplastic composite electrodes. Journal of Materials Processing Technology, 2004, 149: 278-283
[11] Q. H. Zhang, J. H. Zhang, S. F. Ren et al. Study on technology of ultrasonic vibration aided electrical discharge machining in gas. Journal of Materials Processing Technology, 2004, 149: 640-644
[12] Fabio N. Leao., Ian R. Pashby. A review on the use of environmentally-friendly dielectric fluids in electrical discharge machining. Journal of Materials Processing Technology, 2004, 149: 341-346
[13] 宋博岩,赵万生,张宏.绿色电火花加工的概念.电加工与模具,2000(6):4-6
[14] 曹凤国,翟力军,杨大勇等.从第14届国际电加工学术会议看电火花加工技术的发展趋势.电加工与模具,2004(5):1-6
[15] 张龙.混粉电火花加工及其镜面加工技术的实验研究:(硕士学位论文).大连:大连理工大学,2003.
[16] MING Q Y, HEL Y. Powder-suspension Dielectric Fluid for EDM. J. Material Process Technology, 1995, 52(1): 44-54
[17] 孟庆国,赵万生,李文卓.粉末特性对混粉电火花镜面加工的影响.电加工与模具.2000,4:13-17
[18] 赵万生,孟庆国,刘维东,王振龙.混粉电火花镜面加工技术的研究及进展.2001,12(4):446-450
[19] 孟庆国,赵万生,李文卓,董玉文.混粉电火花镜而加工表面性能研究.中国表面工程.2001,52(3):41-44
[20] MING Q Y, HEL V. Powder-suspension Dielectric Fluid for EDM. J. Material Process Technology, 1995, 52(1): 44-54
[21] 王振龙,赵万生.微细电火花加工中电极材料的蚀除机理研究.机械科学与技术.2002,21(1):124-126
[22] J. Simao, H. G. Lee, D. K. Aspinwall et al. Workpiece surface modification using electrical discharge machining. International Journal of Machine Tools & Manufacture, 2003, 43(9): 121-128
[23] 孟庆国.混粉电火花镜面加工工艺及其表面特性研究:(博士学位论文).哈尔滨:哈尔滨工业大学,2000
[24] W.F.休斯,J.A.布赖顿.孙宗扬译.全美经典:近代物理学.北京:科学出版社,2002
[25] Yoshiyuki UNO, Akira OKAKA, Yasyguri HAYASH Ietal. Surface Modification by EDM with Nickel Powder Mixed Fluid.
[26] 索来春,赵万生,梁力平等.混粉电火花加工极间介质击穿机理的研究.电加工与模具,2001(5):10-13
[27] 李明辉.电火花加工理论基础.北京:国防工业出版社,1989.335
[28] 杨津基.气体放电北京:科学出版社,1983.18-32
[29] 赵凯华,陈熙谋.电磁学.第二版(上册).北京:高等教育出版社,1985.322-325
[30] 胡志强,甄汉生,施迎难.气体电子学.北京:电子工业出版社,1985.126-128
[31] 索来春,刘远韬,赵万生,梁力平,聂东.混粉电火花加工放电通道流体动力学和热动力学分析.航空精密制造技术,2001,37(5):8-10
[32] 方俊鑫,殷之文.电介质物理学.北京:科学出版社,1989.10-20
[33] 刘绍璞等.金属化学分析概论与应用.成都:四川科学技术出版社,1983
[34] 埃同娟等.金属化学分析指南.贵州人民出版社,1988
[35] 索来春,赵万生,赵军.混粉工作液镜面电火花加工试验装置的研制.机械设计与制造,2003,1:115-116
[36] 何广敏,赵万生,郭永丰.混粉镜面电火花加工工作液循环装置的研制.机械工程师,1999,1:21-22
[37] 索来春,孟庆国,赵新通,赵万牛.混粉电火花加工搅拌系统的设计.航空精密制造技术,1999,35(2):13-15
[2] 朱玲龙,杨连文,赵福令.混粉电火花加工工艺初探.电加工,1999(5):25-27
[3] K. H. Ho, S. T. Newman. State of the art electrical discharge machining(EDM). International Journal of Machine Tools & Manufacture, 2003, 43(10): 1287-1300
[4] Y. S. Wong, L. C. Lim, Iqbal Rahuman et al. Near-mirror-finish phenomenon in EDM using powder-mixed dielectric. Journal of Materials Processing Technology, 1998, 79: 30-40
[5] 徐小兵,毛利尚武.日本电火花加工技术的发展动态.电加工与模具,2003(1):1-3
[6] 吴敏镜.漫谈电火花加工的发展与展望.新技术新工艺,1999(5):13-15
[7] P. M. George, B. K. Raghunath, L. M. Manocha, Ashish M. Warrier. EDM machining of carbon-carbon composite—a Taguchi approach. Journal of Materials Processing Technology 2004,145(7):66-71
[8] D. T. Pham, S. S. Dimov, S. Bigot et al. Micro-EDM—recent developments and research issues. Journal of Materials Processing Technology, 2004, 149: 50-57
[9] 何广敏,赵万生,郭永丰等.混气电火花镜面加工的研究.制造技术与机床,2000(3):43-45
[10] A. Curodeau., M. Richard, L. Frohn-Willeneuve. Molds surface finishing with new EDM process in air with thermoplastic composite electrodes. Journal of Materials Processing Technology, 2004, 149: 278-283
[11] Q. H. Zhang, J. H. Zhang, S. F. Ren et al. Study on technology of ultrasonic vibration aided electrical discharge machining in gas. Journal of Materials Processing Technology, 2004, 149: 640-644
[12] Fabio N. Leao., Ian R. Pashby. A review on the use of environmentally-friendly dielectric fluids in electrical discharge machining. Journal of Materials Processing Technology, 2004, 149: 341-346
[13] 宋博岩,赵万生,张宏.绿色电火花加工的概念.电加工与模具,2000(6):4-6
[14] 曹凤国,翟力军,杨大勇等.从第14届国际电加工学术会议看电火花加工技术的发展趋势.电加工与模具,2004(5):1-6
[15] 张龙.混粉电火花加工及其镜面加工技术的实验研究:(硕士学位论文).大连:大连理工大学,2003.
[16] MING Q Y, HEL Y. Powder-suspension Dielectric Fluid for EDM. J. Material Process Technology, 1995, 52(1): 44-54
[17] 孟庆国,赵万生,李文卓.粉末特性对混粉电火花镜面加工的影响.电加工与模具.2000,4:13-17
[18] 赵万生,孟庆国,刘维东,王振龙.混粉电火花镜面加工技术的研究及进展.2001,12(4):446-450
[19] 孟庆国,赵万生,李文卓,董玉文.混粉电火花镜而加工表面性能研究.中国表面工程.2001,52(3):41-44
[20] MING Q Y, HEL V. Powder-suspension Dielectric Fluid for EDM. J. Material Process Technology, 1995, 52(1): 44-54
[21] 王振龙,赵万生.微细电火花加工中电极材料的蚀除机理研究.机械科学与技术.2002,21(1):124-126
[22] J. Simao, H. G. Lee, D. K. Aspinwall et al. Workpiece surface modification using electrical discharge machining. International Journal of Machine Tools & Manufacture, 2003, 43(9): 121-128
[23] 孟庆国.混粉电火花镜面加工工艺及其表面特性研究:(博士学位论文).哈尔滨:哈尔滨工业大学,2000
[24] W.F.休斯,J.A.布赖顿.孙宗扬译.全美经典:近代物理学.北京:科学出版社,2002
[25] Yoshiyuki UNO, Akira OKAKA, Yasyguri HAYASH Ietal. Surface Modification by EDM with Nickel Powder Mixed Fluid.
[26] 索来春,赵万生,梁力平等.混粉电火花加工极间介质击穿机理的研究.电加工与模具,2001(5):10-13
[27] 李明辉.电火花加工理论基础.北京:国防工业出版社,1989.335
[28] 杨津基.气体放电北京:科学出版社,1983.18-32
[29] 赵凯华,陈熙谋.电磁学.第二版(上册).北京:高等教育出版社,1985.322-325
[30] 胡志强,甄汉生,施迎难.气体电子学.北京:电子工业出版社,1985.126-128
[31] 索来春,刘远韬,赵万生,梁力平,聂东.混粉电火花加工放电通道流体动力学和热动力学分析.航空精密制造技术,2001,37(5):8-10
[32] 方俊鑫,殷之文.电介质物理学.北京:科学出版社,1989.10-20
[33] 刘绍璞等.金属化学分析概论与应用.成都:四川科学技术出版社,1983
[34] 埃同娟等.金属化学分析指南.贵州人民出版社,1988
[35] 索来春,赵万生,赵军.混粉工作液镜面电火花加工试验装置的研制.机械设计与制造,2003,1:115-116
[36] 何广敏,赵万生,郭永丰.混粉镜面电火花加工工作液循环装置的研制.机械工程师,1999,1:21-22
[37] 索来春,孟庆国,赵新通,赵万牛.混粉电火花加工搅拌系统的设计.航空精密制造技术,1999,35(2):13-15