弹性基体磨具的磨抛轨迹与表面加工质量研究

Polishing Trajectory and Surface Machining Quality of Elastic Matrix Abrasive Tool

目的解决以光学玻璃为代表的硬脆材料加工效率与表面质量难以同时得到保证的共性问题。方法以弹性基体工具磨削抛光技术为基础,分析弹性接触区域内有效工作磨粒的运动行为。基于Preston方程材料去除模型,研究磨抛过程中磨抛接触区域的接触面积、速度分布、多颗磨粒的运动轨迹。基于运动学模型,探究磨抛过程中磨具的运动学参数、磨粒浓度及排布特征等因素对磨粒磨抛轨迹的影响,采用磨具与工件接触区域磨粒运动轨迹相对面积占比和变异系数表征磨粒运动轨迹分布的均匀性,并建立基于轨迹均匀性的加工表面质量评价方法,优化工艺参数。以石英玻璃为加工对象,以硅橡胶中混入金刚石磨粒为基体,通过正交实验研究不同参数对工件表面质量的影响。结果仿真结果表明,选取自转速度为300 r/min、进给速度为1 mm/s、磨抛进动角为15°,磨粒浓度及排布采用1 mm磨粒理论间距,此时获得的最大磨粒运动轨迹相对面积占比为96.46%,最小变异系数为0.375。通过实验,得到了选取磨抛工艺参数中的最佳参数组合,自转速度为1200 r/min,进给速度为1 mm/s,磨抛进动角为15°~20°,磨粒浓度及排布采用磨粒间距1 mm,该组合可将工件的表面粗糙度由1.078μm降至0.057μm,材料去除率为3.8×108μm^(3)/min。结论磨粒运动轨迹的密集程度与自转速度、磨粒浓度及排布呈正相关,与进给速度呈负相关,在考虑加工成本的前提下,采用高自转速度、高磨粒浓度、低进给速度及15°~20°的进动角可以获得密集且均匀的磨粒运动轨迹,提高了工件的表面质量和材料去除效率。

Due to their excellent physical and chemical properties,hard and brittle materials represented by the optical glass are massively used in high-end optoelectronic fields such as optical imaging,laser fusion,solar cells,space observation,and sensors.However,the ultra-high hardness,strength,brittleness,and chemical stability make such materials face significant challenges in practical processing and manufacturing.In response to these issues in precision and ultra-precision machining,in terms of grinding,lapping,and polishing,the material removal efficiency,and surface finish quality are brutal to ensure simultaneously.This work aims to ensure the machining efficiency and machined surface quality of the elastic grinding and polishing process by considering the influence of the abrasive particle motion trajectory according to the Hertz elastic contact model and Preston material removal mechanism.By derivating the movement function of effective working abrasive grains in the contact area between the tool and the workpiece,the effects of the precession angle,rotation speed,feed speed of the abrasive tool,and the concentration and arrangement characteristics of abrasive grains on the abrasive particle grinding trajectory were comprehensively analyzed.The grinding trajectory uniformity was characterized by the contact area share of the grain path and the coefficient of variation.The surface quality evaluation approach was developed on trajectory uniformity to guide the process parameters optimization.The simulation results indicated that the maximum area share of the abrasive particle trajectory was 96.46%and the minimum coefficient of variation was 0.375.It was achieved when the rotation speed was 300 r/min,the feed speed was 1 mm/s,the precession angle was 15°,and the abrasive grain spacing was 1 mm.For the experiment validation,the quartz glass was selected as the workpiece and processed by the polishing tool fabricated with silicone rubber as the bonding matrix and diamond grains as the abrasives.The effects of the kinematic parameters of the abrasive tool and the concentration and arrangement characteristics of abrasive grains on the surface quality of the workpiece were studied by orthogonal experiments.The surface roughness and micro-morphology of quartz glass were measured with a roughness tester and observed by a three-dimensional profiler.The material removal rate was calculated through the weight loss of the workpiece.The surface quality of the machined quartz glass before and after polishing was analyzed and compared.The experimental results showed that the optimal output was obtained by the process parameter combination where the rotation speed was 1200 r/min,the feed speed was 1 mm/s,the precession angle was 15°to 20°,and the abrasive grain spacing was 1 mm.As a result,the surface roughness of the workpiece was decreased from 1.078μm to 0.057μm,and the material removal rate was 3.8×108μm^(3)/min.The practical application of elastic matrix tools in the precision machining of hard and brittle materials helps to obtain a smooth and uniform surface finish.In conclusion,to improve the workpiece's processing efficiency and surface quality,this study discussed the influence of the kinematic parameters of the polishing tool and its abrasive grains arrangement and trajectory.The theoretical analysis and modeling could be employed to develop high-efficiency and high-quality ultra-precision grinding and polishing technology.The density of abrasive grain trajectory is positively correlated with rotation speed,abrasive grain concentration and arrangement,and negatively correlated with feed speed.Considering the processing cost,dense and uniform abrasive grain trajectory can be obtained by adopting high rotation speed,high grain concentration,low feed speed and 15°to 20°precession angle,which improves the surface quality of workpiece and material removal efficiency.