基于压力分布的环摆式双面抛光去除均匀性研究

Removal Uniformity in Ring-Pendulum Double-Sided Polishing Based on Pressure Distribution

构建了一种基于速度和压力分布模型的材料去除量分布计算模型。建立了环摆式双面抛光的有限元模型,对5种半径的上抛光盘在不同加工压力下与元件接触面的压力分布进行分析,通过拟合得到压力分布特性模型。根据Preston方程,将压力分布模型与速度分布模型耦合,得到材料去除量分布计算模型。通过模拟加工计算,研究加工压力和上抛光盘尺寸对去除量分布及均匀性的影响,发现去除量分布主要受上抛光盘尺寸和摆动距离的影响,去除均匀性主要受加工压力的影响。通过加工实验,对所得到的材料去除量分布计算模型的准确性进行验证,并研究了加工压力和上盘尺寸对材料去除量分布及均匀性的影响。实验结果表明,上抛光盘的直径越大,则加工压力越小,材料去除的均匀性越好。基于去除量分布预测模型,利用得到的规律指导实际加工,选取初始表面面型峰谷(PV)值为2.09λ(λ=632.8 nm)、均方根(RMS)值为0.464λ的熔石英样件,通过材料去除量预测模型得到工艺参数的最优解。加工后元件表面面型PV值降至0.85λ,RMS值降至0.137λ。所提模型将元件表面PV值降低到λ以下的时间缩短至原来的50%,实现了元件表面面型的快速收敛。

Objective Ring-pendulum double-sided polishing,a novel type of double-sided polishing process,enables simultaneous processing on the upper and lower surfaces of the components,reducing polishing parallelism errors and enhancing processing efficiency.However,currently,the processing primarily relies on technicians using trial-and-error methods,to accumulate experience for selecting appropriate process parameters.This approach lacks controllability and repeatability,mainly because the prediction of the surface pre-processing is based on the relative speed between the abrasive grain and the component surface,and the number of scribes to calculate the distribution of material removal.This method overlooks the influence of contact surface pressure on the material removal.As a result,discrepancies arise between predicted outcomes and the actual distribution of polished material removal,failing to provide an effective guide for the decision-making on process parameters.Methods We analyze the working principle of the ring-pendulum double-sided polishing equipment,carry out a kinematic analysis of abrasive particles,and obtain the instantaneous relative velocity field distribution between the polishing disc and the component surface.We examine the influence of polishing pressure on the component’s processing surface,establish a finite element model of the pressurized cylinder,component,and polishing disc,set constraints according to the pressure loading situation during actual processing,and conduct finite element simulation analysis.Our analysis yields the pressure distribution law on the component surface under both self-weight and pressurized conditions of the upper polishing disc.The data are fitted using the least squares method to construct a pressure distribution model of the contact surface between the ring-pendulum double-sided polishing element and polishing disc.By coupling the instantaneous relative velocity field model of the element and the polishing disc with the pressure model of the contact surface,we derive the instantaneous removal at each point on the component surface according to Preston’s equation.The summation of instantaneous removal constructs the prediction model for material removal in ring-pendulum double-sided polishing.Results and Discussions In this study,we select 430 mm×430 mm×10 mm fused silica elements for practical process experiments.Three components with different initial face types are chosen for processing.The accuracy of the material removal prediction model is verified through three comparative experiments.We investigate the effects of processing pressure and upper disc size on the distribution and uniformity of material removal.Experimental results indicate that larger diameters of the upper polishing disc and lower machining pressures contribute to better uniformity in material removal.Conclusions Guided by the removal distribution prediction model,we apply the derived principles to actual processing.Fused silica samples with an initial surface profile peak-valley(PV)value of 2.09λ(λ=632.8 nm)and a root mean square(RMS)value of 0.464λare selected.Through the material removal prediction model(Fig.25),we obtain optimal solutions for process parameters.After processing,the surface PV of the component is reduced to 0.85λ,and the RMS value decreases to 0.137λ(Fig.26).The time required to reduce the component surface PV belowλis cut to 50%of the original duration,achieving rapid convergence of the component surface profile.