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磨料群可控排布砂轮的制备技术及其磨削性能
Fabrication Technology of the Wheel with Controlled Abrasive Cluster and Its Grinding Performance
【作者】 袁和平;
【导师】 高航;
【作者基本信息】 大连理工大学 , 机械制造及其自动化, 2010, 博士
【摘要】 磨削技术向着高速、高效和精密方向发展,以及飞速发展的新材料带来的磨削加工需求,对传统磨具提出了新的挑战。一方面,传统固结磨料磨具,特别是精密磨削磨具,由于磨粒十分细小、磨粒分布紧密、容屑空间小,造成磨削过程中磨具工作表面极易堵塞、导致磨具过早失效、工件磨削热损伤甚至正常加工无法进行。另一方面,传统单层超硬磨料砂轮,砂轮精度过度依赖于基体精度及安装配合精度。为了解决传统磨具存在的上述缺陷,本文提出了磨料群可控排布砂轮,即磨具中的磨粒或磨料群及其间距能够按照使用要求进行科学地排列或分布,磨料群可以为单层或多层磨粒结构,且能够确保合理的容屑空间。首先对磨料群可控排布砂轮进行参数化表征,分析了磨料群主要参数的关系,并从磨削理论和磨粒运动学的角度分析了砂轮表面主要参数的对磨削性能的影响,建立了包含磨料群直径、有效面积比、磨料群运动轨迹密度等指标的磨料群可控排布砂轮表征与评价体系。对不同排布样式的磨料群可控排布砂轮、不同磨料群间距、不同砂轮转速的磨削轨迹密度计算和分析,为磨料群可控排布砂轮设计和工艺参数选取提供依据。提出了经济简单的磨料群可控排布电镀砂轮的制备工艺——选择性复合电沉积,并研究了主要的基础工艺:包括基于丝网印刷技术、照相制版技术、激光打孔技术的掩模制备方法和工艺及其适用范围;通过正交试验对脉冲电镀镍钴合金砂轮制备体系的主要工艺参数的优化选取;制定了复合电沉积工艺规范并研制了适合小批量试验和生产的半自动化电镀砂轮制备系统,成功制备出几种端面磨削和周边磨削用磨料群可控排布砂轮样件。为减小安装后的电镀砂轮工作表面圆跳动误差,研制了具有多层磨料的微磨料群可控排布电镀镍钴合金砂轮,提出了基于电解加工方法的磨料群可控排布镍钴合金镀层砂轮的电解修整技术,根据标准电极电位理论和极化曲线测试研究了镍钴合金镀层电解去除的可行性;砂轮安装到主轴后工作表面圆跳动误差减小到初始值的61.5%,显著提高了砂轮的使用精度;电镀多层CBN砂轮电解修锐中镍钴合金结合剂去除均匀,磨粒平均出刃高度达到磨粒粒径的42.9%。结合航天企业对碳纤维/环氧树脂复合材料构件的磨削加工需求及其干磨削的难题,进行了磨料群可控排布电镀砂轮的磨削碳纤维/树脂复合材料的试验。连续磨削中磨料群可控排布砂轮的轴向力稳定、工件表面完整性较好,工件表面粗糙度Ra值稳定在0.8至1.3μm之间;由于磨削温度低于树脂软化温度未发生树脂和切屑软化粘附现象,磨料群之间的间隙容纳了大量的切屑、方便切屑转移,有效地防止砂轮堵塞。根据新型砂轮加工碳纤维复合材料优异的磨削性能,将其装备于ZM1000型数控高速钻磨机床上,在某碳纤维/树脂复合材料筒状构件干磨削加工中得到了应用。
【Abstract】 With grinding technology developing toward high speed, high efficiency and high accuracy, and grinding needs from booming new materials, challenges are posed to the conventional grinding wheels. On the one hand, on the traditional fixed abrasive wheel, especially for precision grinding, the grain is so little and the chip clearance is so small that the tool surface are prone to be loaded, causing the tool invalid and the workpiece burned even the normal machining process unable to continue. On the other hand, the accuracy of traditional single layer superabrasive wheel depends on the accuracy of wheel substrate significantly. To solve these problems in traditional grinding wheel, a wheel with controlled abrasive cluster is proposed in this paper, on which the distance between the grits or abrasive clusters and the distribution pattern are set suitably with practice. Monolayer or multilayer abrasives are feasible and the chip clearance is ensured properly.Firstly, the wheel with controlled abrasive cluster is characterized by parameters and the relationship of the abrasive-cluster’s main parameters is analyzed. Also the effect of the main parameters of the wheel surface on the grinding performance is studied at the point of view of grinding theory and grit kinematic analysis. A characterization and evaluation system was established, which contains such as diameter of abrasive cluster, the effective abrasive index, the kinematic tracks of the abrasive clusters and so on. The density of grinding tracks of cluster on the wheel with different distribution patterns, with different distance between the clusters and different rotation speed of wheel, are calculated and analyzed. They provide a basis for choosing the parameters of the wheel design and machining.An economical and easy fabrication process of selective composited electro-deposition is proposed and the main processes are studied. The method and processes of mask fabrication are explored and their available ranges are given based on the following three aspects:the screen printing technology, the photolithography technology and the laser drilling. The main parameters of pulse plating of Nickel-Cobalt alloy are optimized and chosen by orthogonal experiments. The process specification for the wheel fabrication is set and a semi-automatic electroplating equipment fulfilling for small batch experiment and production is developed. Some samples of the wheel with controlled abrasive cluster are fabricated successfully.To reduce or eliminate the run-out error of the wheel working surface after it to be assembled, the multi-layer abrasive electroplated Ni-Co wheel with controlled abrasive cluster is developed. And then, the process of electrolytic dressing is proposed for the Ni-Co electroplated wheel based on electrolytic machining. By analyzing the standard electrode potential and testing the polarization curve, the removal feasibility of electroplated Ni-Co alloy by electrolytic dressing is studied. In the experiment of electrolytic dressing on a straight wheel, the surface run-out error after assembled on the grinder spindle has a reduction by 61.5% compared with dressed before, which improve the wheel use accuracy significantly. In the experiment of electrolytic dressing on multi-layer abrasive wheels, the Ni-Co alloy bonding of the wheel is removed uniformly and the average protrusion height is up to 42.9% of the grain size.In order to fulfill with the needs of machining of carbon fiber reinforced plastics (CFRP) and solve the difficulties of dry grinding of CFRP, grinding experiments by using the wheel with controlled abrasive cluster are conducted. The results show that the grinding temperature is dramatically reduced. The steady axial force and good surface integrity are obtained by using the wheel with controlled abrasive cluster, and the surface roughness Ra of the workpiece keeps in a range from 0.8 to 1.3μm. There is no soften resin and chips because the grinding temperature is lower than the soften temperature of the epoxy resin. The space among the clusters serve as room and access for grinding chips accommodation and removal, which avoids wheel loading effectively. Due to the excellent performance of the new wheel on grinding of CFRP, the wheel with controlled abrasive cluster is equipped on the high speed drilling and grinding CNC machine typed ZM1000 and applied in grinding of a certain cylindraceous composites part.