计算机控制光学表面成形技术的驻留时间算法

为了提高镜片的加工精度与效率,利用计算机控制光学表面成形技术(CCOS)的抛光方法对光学镜片进行抛光全过程动态仿真。根据Preston方程建立材料去除函数模型,对抛光过程中压力、转速以及工件与抛光磨头相对半径比对抛光去除速率的影响进行分析。为建立球面镜片的动态全过程仿真,结合卷积原理,推导加工残余误差与去除函数和驻留时间三者间的线性关系,根据镜片的对称性,将元素个数从2m+1点简化为m+1点,以提高运算效率。最后为获得仿真最小残余误差,采用非负最小二乘法求解驻留时间。结果表明,材料去除速率函数类似于高斯分布,抛光后能使镜片面形误差收敛,对模拟表面进行仿真,半径为100mm的镜片其初始表面形貌粗糙度的均方根值从0.467μm收敛到0.028μm,轮廓最大高度从6.12μm收敛到1.48μm。对实测表面进行加工仿真同样令其表面形貌粗糙度的均方根值从3.007μm收敛到0.107μm,轮廓最大高度从160.73μm收敛到13.76μm,因此提出的驻留时间求解方法对于球面镜片抛光全过程动态仿真有一定的可行性。     

Utilisation of time-variant influence functions in the computer controlled polishing

In the computer controlled polishing, a polishing tool moves in a well-defined manner across the workpiece surface in order to individually remove the surface error-profile. The commonly used technique to calculate the moving of the polishing tool is the dwell time method. Based on a constant (time-invariant) removal characteristic of the polishing tool (influence function) the amount of material to be removed is controlled via the dwell time. The longer the polishing tool is in contact with a particular area of the workpiece, the more material is removed at this position.Mathematical basics to calculate dwell time-profiles are shown, and a new approach considering time-variant influence functions for the computer controlled polishing is introduced. The results point out that time-variant influence functions may contribute to further decrease the process time, and thus to make a computer controlled polishing process more efficient. The reduction of the process time was observed to approximately 35% using a combination of the dwell time method with time-variant influence functions.     

Real-time computer controlled backscatter measurement of optical fibres

The software implementation of a real-time computer-controlled backscatter measurement system for a high standard conformance testing procedure for optical fibres is discussed. Optical time domain reflectometry (OTDR) techniques are employed to test fibre reels along or at the end of a production line. A high speed computer is integrated with such a device to automate a chain of practical test procedures. Significant enhancements have been achieved with the use of fast computer integration, notably up to an eight-fold reduction in test time with no loss of measurement accuracy, when compared to a current commercial system.     

Finite element analysis of the influence of tool edge radius on size effect in orthogonal micro-cutting process

The size effect in metal cutting is evident in the nonlinear scaling phenomenon observed in the specific cutting energy with decrease in uncut chip thickness. It has been argued by many researchers that this scaling phenomenon is caused mainly by the cutting tool edge radius, which purportedly affects the micro-cutting process by altering the effective rake angle, enhancing the plowing effect or introducing an indenting force component. However, the phenomenological reasons why the tool edge radius causes size effect and the relationship between the tool edge radius and the characteristic length scale associated with the size effect in micro-cutting has not been sufficiently clarified. In this paper, a strain gradient plasticity-based finite element model of orthogonal micro-cutting of Al5083-H116 alloy developed recently is used to examine fundamentally the influence of tool edge radius on size effect. The applicability of two length scales—tool edge radius and the material length scale l in strain gradient plasticity—are also examined via analysis of data available in the literature.     

Cutting force model considering tool edge geometry for micro end milling process

The analysis of the cutting force in micro end milling plays an important role in characterizing the cutting process, as the tool wear and surface texture depend on the cutting forces. Because the depth of cut is larger than the tool edge radius in conventional cutting, the effect of the tool edge radius can be ignored. However, in micro cutting, this radius has an influence on the cutting mechanism. In this study, an analytical cutting force model for micro end milling is proposed for predicting the cutting forces. The cutting force model, which considers the edge radius of the micro end mill, is simulated. The validity is investigated through the newly developed tool dynamometer for the micro end milling process. The predicted cutting forces were consistent with the experimental results.     

Modeling and predicting for surface topography considering tool wear in milling process

This paper presents a model for the prediction of surface topography considering tool wear during the milling process. First, the cutting edge path equation, which can be transformed into equivalent polynomial equations and solved for discrete positions along the feed direction, is established including the effect of tool wear. Then, cutting edge is divided into a series of cutting points and an algorithm is proposed to determine the range of divided position angle. Finally, surface topography model is established based on the established cutting path equation, the range of position angle, the calculated cutting time, and spiral lag angle. By using this model, surface topography generation is simplified with respect to other models in literature and the modeling method of surface topography does not need to mesh the workpiece and the model can easily be extended to include other factors on surface generation. Based on the established surface topography model, an algorithm is proposed to simulate generation of surface profile in milling operation. Experimental work and validation of the established model is performed on a five-axis milling center by using stainless steel 1Cr18Ni9Ti and cemented carbides milling cutter. Cutting test results about the topography generation of the plane and cylindrical surface show good agreement with model predictions.     

Polishing tool for optical materials

The influence of various abrasive materials on the polishing of lithium-niobate single crystals is studied experimentally. In the analysis of the polishing tool, the tool life, the productivity, and the quality of the machined surface are taken into account.     

Modeling of the effect of tool edge radius on surface generation in elliptical vibration cutting

The elliptical vibration cutting (EVC) technique has been found to be a promising technique for ultraprecision machining of various materials. During the EVC process, two-dimension vibration movement of the cutting tool generates consecutively overlapping EVC cycles. In each cycle, the tool position relative to the workpiece gets continuously varied, and meanwhile, cusps are left along the nominal cutting direction. Such vibration marks, which have never been found in conventional cutting process, are considered to be a critical characteristic for the EVC technique. In order to analyze this unique characteristic, an analytical model based on geometrical relationships in the EVC process was developed to calculate the theoretical roughness, where the tool edge is assumed to be perfectly sharp. However, the effect of tool edge radius is probably significant, especially in the situation where the tool edge radius is comparable to the vibration amplitudes. Hence, in the present research, an analytical surface generation model for the EVC process is developed to better understand the surface generation process and predict the surface roughness. The tool edge radius is considered and investigated in detail in this new approach. Mathematical evaluation shows that the surface roughness value along the nominal cutting direction decreases with the increase of the edge radius. In order to validate the proposed model, a series of EVC grooving tests on soft and hard work materials were conducted using a polycrystalline diamond (PCD) tool by applying the ultrasonic EVC technique. The results show that the predicted roughness based on the proposed model correlates well with the experimental results measured by a white light interferometer, and the model considering the tool edge radius performs significantly better than the one without considering the edge radius in predicting the roughness along the nominal cutting direction.     

基于受控赋时Petri网的批处理系统建模

将受控赋时Ｐｅｔｒｉ网用于批处理生产过程中离散事件的建模。通过为动作库所赋予不同的时间参数,可对批处理对程中特有的零等待与有限时间等待中间存储策略进行建模和分析,控制库所的引入可消除资源争用冲突。借助与建立的模型,可进一步对系统进行逻辑分析和控制综合研究。     

Modeling of the static tool influence function of bonnet polishing based on FEA

The purpose of this paper is to investigate the model of the static tool influence function (sTIF) of bonnet polishing (BP). Three kinds of sTIF are mathematically modeled, which are static tool influence function of tilted polishing (sTIF_t), static tool influence function of discrete precession polishing (sTIF_d), and static tool influence function of continuous precession (sTIF_c), respectively. Pressure distribution in the contact area is confirmed based on finite element analysis (FEA) technology. A group of experiments to extract the polishing spots have been conducted to verify the accuracy of the sTIF model. Meanwhile, the difference between sTIF_d and sTIF_c is studied. It turns out that the removal depths of sTIF_d and sTIF_c are almost the same, and the continuous precession polishing can be replaced by discrete precession polishing to ease control in practical polishing process especially for the aspheric surfaces polishing.     

计算机辅助产品创新集成工具的框架

通过对产品设计过程的分析，介绍了在产品设计过程中质量功能配置、发明问题解决理论和稳健设计的理论，阐述了这些理论在产品设计中的应用，提出了计算机辅助创新集成工具的框架，并以汽车车门的设计为实例，对该工具的使用作了进一步说明。     

Effect of edge preparation technologies on cutting edge properties and tool performance

The International Journal of Advanced Manufacturing Technology - Edge preparation has gained widespread use due to its low cost and high impact. Various edge preparation methods are reported in the...     

Scanning electron microscopic technique for imaging a diamond tool edge

A technique is described to measure the edge radius of diamond cutting tools using the scanning electron microscope (SEM). This method attempts to overcome two major limitations of the SEM in this application: low image contrast and lack of quantitative topographic information. A line of electron beam contamination, viewed at an angle, provides improved contrast for focusing and a means of obtaining the tool profile from the geometry.     

Selecting the cutting edge of a shaping tool

The determination of the cutting-edge parameters in sharpening a shaping tool is considered, for purposes of automatic design.     

计算机控制系统的可靠性分析

可靠性与技术性能是计算机控制系统的两个最重要的方面,但在具体设计工作中,往往特别强调系统的技术性能而忽略了可靠性,尤其是忽略软件可靠性,这常常导致系统不能正常工作,造成经济损失,甚至危及生命安全.本文介绍了计算机控制系统的可靠性的定量表示方法,分析了软件可靠性及硬件可靠性对系统可靠性的影响,对解决办法作了一些探讨.     

Identification of suitable process parameters for friction surfacing of mild steel with AA6063 aluminium alloy

The present study is aimed at identifying suitable process parameters for friction surfacing of IS2062 mild steel with AA6063 aluminium alloy and obtain relationships between the input parameters and the process response that can be used for sound coating with adequate strength and ductility. Factorial experimental design technique was used to investigate and select the parameter combination to achieve adequate strength and ductility. Mechatrode rotational speed, axial load and substrate traverse speed were observed to be the most significant factors on the process response. Based on the results, it was observed that (i) lower axial load and traverse speed with high rotational speed and (ii) higher axial load and traverse speed with lower rotational speed produced sound coatings. It has also been observed that sound coatings could be obtained in a narrow set of parameter range as the substrate-coating materials are metallurgically incompatible and have propensity to form brittle intermetallics.