KDP晶体单点金刚石超精密切削加工的发展

总结了KDP晶体材料优异的光学性能及其难加工的机械物理特性,并回顾了KDP晶体单点金刚石切削(SPDT)加工的起源,特别对KDP晶体SPDT加工技术的国内外发展状况做了着重介绍,最后展望了KDP晶体SPDT加工的未来发展趋势。     

超精密加工中刀具参数对脆性材料非球面加工质量的影响

脆性材料的光学非球面零件以其特有的优势,在军用和民用产品中越来越普及。光学非球面器件材料有一系列不利于加工的特点,被公认为是最难加工的光学零件。概述了超精密加工中单点金刚石车削技术在脆性材料非球面加工中的应用,并详细地分析了单点金刚石车削加工时刀具几何参数、X偏置、刀具半径补偿对非球面加工表面质量的影响。     

超精密加工中刀具参数对脆性材料非球面加工质量的影响

脆性材料的光学非球面零件以其特有的优势,在军用和民用产品中越来越普及.光学非球面器件材料有一系列不利于加工的特点,被公认为是最难加工的光学零件.概述了超精密加工中单点金刚石车削技术在脆性材料非球面加工中的应用,并详细地分析了单点金刚石车削加工时刀具几何参数、X偏置、刀具半径补偿对非球面加工表面质量的影响.     

KDP晶体各向异性对切削力的影响研究

对KDP晶体单点金刚石切削中动态切削力产生的原因及变化规律进行深入研究,以揭示材料各向异性对KDP晶体超精密加工切削力的影响。以微观塑性力学和断裂力学理论为基础,建立了切削力新模型,并优选出最佳晶体切削方向,以降低由材料各向异性引起的切削力波动对加工表面质量的影响。     

KDP晶体表面波纹度的分析与研究

针对工艺参数对KDP晶体表面波纹度值的影响问题,基于二次通用回归旋转组合方法优化KDP晶体单点金刚石飞刀切削工艺参数组合,采用单因素和多因素法分析各因素对表面波纹度的影响规律,并以此为基础优化工艺参数,进行KDP晶体切削实验。试验表明:各因素对表面波纹度的影响程度大小顺序为:进给量二次项、进给量、转速、转速与进给量的交互作用。优化出表面波纹度值最小时的加工工艺参数组合:刀具圆弧半径为9mm;转速为633r/min;进给量为11.8μm/r;背吃刀量为21μm,利用此组工艺参数加工出KDP晶体的表面波纹度为0.02μm。     

特殊晶体材料飞刀切削加工工艺的分析与优化

采用二次通用回归旋转组合设计方法,对KDP晶体的切削加工工艺进行优化设计;利用单点金刚石飞刀切削(single point diamond turning,SPDT)技术对其进行切削。对试验结果进行测量与分析,确定合理的试验因素及水平,分析加工工艺参数的单因素和交互因素对KDP晶体表面粗糙度的影响规律。最后得到最优工艺参数组合:刀具圆弧半径为5 mm,转速为800 r/min,进给量为1μm/r,背吃刀量为21μm,加工出的KDP晶体表面粗糙度值为0.017μm。     

KDP晶体表面质量主要影响因素的研究

针对KDP晶体超精密加工过程中出现的表面波纹度和粗糙度问题,采用二次通用回归旋转组合优化设计法及单点金刚石飞刀切削(SPDT)技术,对KDP晶体进行切削实验,对加工过程进行在线监测,利用多因素交互作用分析KDP晶体表面波纹度和粗糙度的影响规律。最后利用偏最小二乘法及lingo软件获得最佳加工工艺参数组合,即当刀具圆弧半径为9mm;转速为800 r/min;进给量为9.184μm/r;背吃刀量为21μm时,加工出KDP晶体的表面波纹度值为0.020μm,表面粗糙度值为0.017μm,对后续能够加工出更大口径(400×400)mm的高质量KDP晶体以满足航空航天领域应用具有重要的实际意义。     

KDP晶体精密切割机设计及其切割表面质量影响因素分析

KDP晶体具有较大的非线性光学系数和较高的激光损伤阈值,但具有易潮解和软脆特性,需要采用精密金刚石线切割实现其坯料的快速切割。基于电镀金刚石环线技术,设计了一种用于KDP晶体快速精密切割设备,能够实现切割张紧力可控可调;采用正交试验方法对200 mm×200 mm的晶体进行切割试验,并通过灰色理论对影响工件平面度和粗糙度的各工艺参数,进行了动态、量化分析,试验得出各工艺因素对切割表面质量影响程度大小,确定了环线切割的最佳工艺参数。     

KDP晶体表面残留颗粒的机器视觉检测方法研究

KDP晶体是一种优质的非线性光学材料,广泛应用于激光核聚变等军工、国防领域。KDP晶体材质特殊,需采用超精密加工技术进行加工,加工过程中的杂质和抛光清洗液中的纳米级羰基颗粒容易吸附在其表面,对其光学特性影响很大。采用机器视觉技术检测晶体抛光清洗后表面残留颗粒,使用光学显微镜获取表面微观图像,经过图像存储、图像增强、边缘检测和图像分割等操作,将残留颗粒特征提取出来,然后进行图像标定、图像测量得到残留颗粒分布状态,对于评价KDP晶体清洗结果、指导清洗过程和保证晶体表面质量有重要作用。     

大口径薄型光学零件弹性夹具优化及夹持变形研究

装夹技术是单点金刚石切削技术(SPDT)的重要组成部分,夹具设计对光学零件的加工精度有重要影响,大口径薄型光学零件装夹时更易产生夹持变形,零件下盘后变形恢复导致面形精度不可控,难以满足加工要求.本文采用有限元仿真分析法,引入正交试验的思路,对夹具设计进行仿真和统计学分析,研究弹性夹具各参数、夹持力和零件径厚比等因素对大...     

Optimal selection of machining parameters for fast tool servo diamond turning

Ultraprecision machined components with micro-structured surfaces in micrometer or nanometer range have gained wide applications especially in optical industry. A technique called fast tool servo (FTS) diamond turning is superior in fabricating precision and complicated micro-structured surfaces with wavelength above tens of microns. However, in order to obtain optimal machined surface quality, the machining parameters need to be selected carefully. In this paper, optimal selection of the machining parameters, including spindle speed, sampling number, feedrate and tool geometry, for fabricating micro-structured surfaces by FTS diamond turning is presented. A simulation system is developed to select feedrate and tool geometry by computing the theoretical surface roughness, spindle speed, and sampling number based on the FTS dynamics and the motion controller capability. Experiments have been carried out to show the effect of the machining parameters. In addition, machining of typical micro-structured surfaces with machining parameters selected by the presented approach proves the effectiveness of the proposed optimal machining parameters selection method and the designed FTS diamond turning machine.     

Diamond milling of an Alvarez lens in germanium

Single crystal diamond milling of optical materials opens up new design degrees-of-freedom for optical engineers. However, parameters for milling of many optical materials have not been investigated, understood, or documented. This paper focuses on the milling of germanium to fabricate a freeform “Alvarez lens” in the mid-wave infrared (MWIR). While the design concepts for such optical systems have been known for decades, implementation has been limited due to difficulty in manufacturing the freeform surfaces. Ultra-precision, multi-axis machining centers can manufacture these surfaces through single crystal diamond milling. A battery of high speed diamond milling tests was performed in germanium to develop the parameters for machining the Alvarez components. Near-surface crystal quality and residual stress measurements using confocal Raman spectroscopy are reported, along with representative test results of the functioning optical system.     

硬脆及黑色金属材料的单点金刚石车削加工技术综述

单点金刚石车削技术是产生纳米特征表面的光学元件重要制造工艺之一。此加工技术在空间科学、生物医学工程、军事、国防和光学等领域有着广泛的应用。然而,金刚石刀具在切削硬脆和黑色金属材料时受到限制,如刀具磨损加剧、刀具寿命缩短以及工件表面加工质量降低等。为了减少刀具磨损和提高工件表面加工质量,相关学者提出了不同的解决方案,将从单点金刚石车削辅助工艺、工件改性、刀具性能改善和超硬材料及刀具方面梳理面向提高硬脆和黑色金属材料加工质量的单点金刚石车削加工技术相关研究,分析当前各种加工技术的优势与局限,提出未来将多种能场辅助的单点金刚石车削技术和基于聚焦离子束改性的金刚石刀具技术作为研究的重点。     

Experimental study on trepanning drilling of the ceramic composite armor using a sintering diamond tool

Laminated ceramic composite armors made of engineering ceramics, fiber-enforced composite, and lightweight alloy are expected to be used widely in armor protection area. However, secondary machining is still a problem for the distinct properties of composing materials, and up to now, few reports can be found out about machining technology. In this work, an experimental study on drilling a typical laminated ceramic composite armor by using a special sintering diamond thinwall trepanning tool has been carried out deeply. To improve the machining efficiency, process parameters including the spindle speed and the axial force have been optimized through drilling experiments. Moreover, the three phases of the whole drilling process of the typical ceramic composite armor is proposed, and the machining mechanism and chip forms in each phase have been analyzed. Also, diamond tool skidding phenomena whether at hole exit or during drilling middle engineering ceramics have been explored, and the skidding mechanisms are presented. In addition, the surface quality of a hole wall machined has been studied, and an advisable measure is given. Results achieved in this paper can provide a technical base for diamond trepanning tool drilling similar laminated ceramic composite armors.     

Cutting force on a diamond grit in stone machining

The present work shows a study on cutting of stone by diamond tool. The diamond grits on the tool surface remove material through the scratching and the cracking of the stone volume. This work reports a kinematics analysis between a single grit of a diamond tool and the stone volume. In previous works, a mathematical relationship of the chipping geometry, due to a single grit, with machining and tool parameters has been derived. This work aims to measure the cutting force due to a single tool grit for different machining conditions. In particular, the machining conditions that are most interesting by an industrial point of view have been investigated. The stone cutting force has been measured by a Kistler 9257 BA piezoelectric platform dynamometer. The outputs of the dynamometer were fed into an A/D converter and sampled at high frequency by a PC. Then, the signals recorded by the PC were filtered by Matlab software at a low frequency. The collected data have been put into relationship with machining and tool parameters.     

Servo piezo tool SPT400MML for the fast and precise machining of free forms

Recent requirements for accuracy and resolution demand higher quality in the machining of precision parts in many industries—such as optics, automotive and aerospace—by free form machining. The required operations are possible by using expensive manufacturing equipment in parallel with several processes such as grinding and polishing. By using a new fast tool servo, the so-called servo piezo tool SPT400MML, driven by a piezoelectric actuator for the precision diamond turning of non-symmetrical surfaces, components can be machined with a fast motion control of the tool (diamond or carbide). The SPT400MML embeds a patented amplified piezoelectric actuator APA400MML and a real-time controller based on a FPGA component able to improve the overall accuracy. Models based on mechanical FEM software and control design software are used to optimise the achieved performances. Experiments have been undertaken to show the capability to displace a diamond tool on a 400-µm stroke with a first resonant frequency of above 600 Hz.     

Microgrooving on electroless nickel plated materials using a single crystal diamond tool

Diamond tools are used in ultra precision machining for their outstanding hardness and crystalline structure, which enable the fabrication of very sharp cutting edges. Single crystal diamond tools are thus extremely useful to machine electroless nickel-plated dies which are generally used for making molds for optical components. This paper deals with the objective to evaluate the performance and suitability of a single crystal diamond tool during microgrooving on electroless nickel plated workpieces. Effects of different machining parameters on overall machining performance were also investigated. The experimental results revealed that long distance (50 km) machining of microgrooves on electroless nickel is possible with a single crystal diamond tool without any significant tool wear. Some groove wear on the rake face were found after machining 28.5 km. No evidence of chipping or wear had been observed on the flank face during the total machining length. The surface roughness range of the machined workpieces was found to be 4–6 nm. Both thrust and cutting components of the machining forces showed an increasing trend with increasing machining distance, though magnitude of the thrust forces were found to increase more than the cutting forces.     

KDP晶体超精密加工技术的研究

通过对KDP晶体等脆性材料的塑性域切削进行理论分析，研究实现脆性材料塑性域切削的条件。激光核聚变KDP晶体的3项主要技术指标是：表面粗糙度、波纹度和透射波前。通过分析影响这3项技术指标的因素。提出了实现KDP晶体精密加工的超精密机床和工艺参数。通过理论分析与实验。研究了晶向、刀具前角、刀具圆弧半径和进给量等参数对表面粗糙度的影响，最终给出KDP晶体精密加工的最佳工艺参数。     

The parameters evaluation and optimization of polycrystalline diamond micro-electrodischarge machining assisted by electrode tool vibration

The objective of this research is to evaluate and optimize machining parameter of tool electrode vibration on micro-electric discharge machining of polycrystalline diamond. The machining parameters evaluated are charge voltage, capacitance, and vibration of the tool electrode. An orthogonal array, signal-to-noise ratio, and analysis of variance are employed to analyze the effect of these machining parameters. The results show that by application of vibration on tool electrode in machining of polycrystalline diamond, it has significant effect up to 66.48% in increasing material removal rate without increasing surface roughness and tool electrode wear. Using Taguchi method for design of experiment, other significant effects on surface quality and tool electrode wear are also investigated. The results also show that surface roughness is mostly affected by the amount of capacitance (52.24%), and the tool electrode wear is also affected by the amount of capacitance (92.82%).     

An integrated method for measurement of diamond tools based on AFM

The measurement and evaluation technology of high precision diamond tools is critically important for supporting the ultra-precision machining. In practical cutting process, the edge profile quality of the diamond tool, including sharpness, micro defects, roughness and tip arc waviness, greatly affects the cutting quality. It is very difficult to measure and evaluate the diamond tool edge profile due to the high precision of tool edge profile and complexity of various measurement parameters. In this paper, an integrated method for measurement and characterization of diamond tools is proposed, which is based on an Atomic Force Microscope (AFM) module. Multiple technical indexes of diamond tools are obtained and validated based on the presented research and cutting experiments, and the evaluation model for each technical index is also proposed. The integrated measurement equipment, including an AFM, precision adjustment device and aerostatic bearings, has been established based on the accuracy requirement of measurement parameters. The edge sharpness, micro defects, surface roughness and tip arc waviness have been obtained based on the evaluation model and experimental data. The experimental results show that the measurement accuracy meets the requirements of the comprehensive evaluation of the diamond tool edge profile. The research work will also contribute to the development of ultra-precision machine.