建立刀具材料磨损性能图的试验方法

基于Ｔａｙｌｏｒ刀具寿命方程，探讨了建立刀具材料磨损性能图的方法，并通过实验进行了验证。从实际应用的角度出发讨论了磨损性能图的含义及使用方法。     

工序质量控制系统的研究

对工序质量控制系统的实现进行了研究.系统可生成质量控制图表对工序质量进行控制.     

An interactive programming system for milling contours and pockets

The programming system discussed here is similar to APT in the definitions it uses. It can automatically generate CNC blocks for the machining of contours and pockets, bounded by linear and circular segments. The system uses simple trigonometry to analyse lines, circles and their intersections. This paper explains a number of algorithms for geometric definitions, elimination of redundant surfaces (thereby optimising the tool path), tool-path generation, etc. A new approach proposed in the present work, based on the construction of a triangle, has simplified the geometry for the case of a circle tangential to two other circles. A number of geometric construction methods and the selection of the milling process (climb versus conventional) for tool-path generation are explained. The system has been modified to machine tapered contour surfaces with a required draft angle.     

Integrating multivariate engineering process control and multivariate statistical process control

Multivariate engineering process control (MEPC) and multivariate statistical process control (MSPC) are two strategies for quality improvement that have developed independently. MEPC aims to minimize variability by adjusting process variables to keep the process output on target. On the other hand, MSPC aims to reduce variability by monitoring and eliminating assignable causes of variation. In this paper, the use of MEPC alone is compared to using the MEPC coupled with MSPC. We use simulations to evaluate the average run lengths (ARL) and the averages of the performance measure. The simulation results show that the use of both MEPC and MSPC can always outperform the use of either alone. To detect small sustained shifts of the mean vector, combing MEPC with a multivariate generally weighted moving average (MGWMA) chart (MEPC/MGWMA) is more sensitive than the MEPC/multivariate exponentially weighted moving average (MEWMA) chart and MEPC/Hotelling’s χ² chart. An example of the application, based on the proposed method, is also given.     

Effect of process parameters on the macrostructure and defect formation in friction stir lap welding of AA5456 aluminum alloy

Friction stir welding could be considered as a suitable technique for joining of aluminum alloys due to the emerging of different problems in fusion welding of these alloys, especially in lap joint designs. For this purpose, it is necessary to optimize the process parameters while in this study, the combined effects of tool rotation and welding travel speed on the macrostructure and defect formation of friction stir lap welding of AA5456 was investigated. The rotating tool was plunged from the 5 mm-thick AA5456-H321 (top sheet) surface into the 2.5 mm-thick AA5456-O (bottom sheet) and lap joints were fabricated by rotational speeds of 300, 600, 800 and 1000 rpm and welding speeds of 15, 30, 60 and 100 mm min⁻¹. The effect of tool rotation and welding speed on the macrostructure, material flow and defect formation, i.e. hooking, kissing-bond and cavity, were studied by optical microscopy and scanning electron microscope. The results declared that hooking height decreased as the welding speed increased while kissing-bond was formed at higher welding speeds. Moreover, hooking region was extended as the tool rotational speed increased. However, at a high rotational speed, cavity was even created.     

A hybrid control scheme to enhance the detection ability of process mean shifts

The hybrid use of Robert’s EWMA and Crosier’s cumulative sum (CUSUM) control schemes is shown to result in a control scheme with high-performance detection of any magnitude of process mean shifts. The parameters of the hybrid scheme are found by adapting the average run length (ARL) to those of a set of locally optimal EWMA schemes in the best way. In this report, an enhancement to the hybrid scheme is considered. First, the ARLs of the hybrid scheme are derived by using the extrapolation method proposed by Waldmann. Second, an optimization of parameter settings is stated and solved. An extensive comparison shows that the ARL properties of the hybrid scheme are comparable to those of the combined Shewhart-CUSUM scheme. Finally, numerical results and examples are presented to demonstrate the efficiency of the hybrid scheme.     

SPC技术在小批量多品种短期生产中的应用

本文分析了传统SPC技术在小批量多品种短期生产中质量控制所存在的问题,应用数理统计方法．得出一种基于正态过程．采取以数据标准化为基础的Z-MR图．可有效用于小批量多品种下对短期生产实施过程质量控制。     

FMS刀具准备系统研究

围绕刀具准备系统的研究与开发 ,论述了刀具准备系统的总体结构和刀具寿命管理、刀具贮备管理、GT概念下刀具分配策略三个功能模块 ,利用相对磨损率来衡量刀具的磨损程度 ,从而对刀具寿命进行优化 ;根据从 MRP和 MPS得到的信息以及刀具的使用数据 ,生成基于成本优化的刀具补充策略 ;并将成组技术、遗传算法及虚拟刀具库思想 ,应用于刀具分配 ,解决FMS中刀具的优化分配问题。     

基于小批量生产的统计过程质量控制研究

分析了在小批量生产环境下实施统计过程质量控制存在的问题,对过程质量特征数据服从正态分布的生产过程,给出了基于概率积分变换理论的控制过程均值、过程方差的标准化控制图的方法,实现了对小批量生产过程的实时控制.     

小批量生产条件下的统计过程控制研究

从小批量生产的定义入手，分析传统的休哈特控制图应用在小批量生产条件下存在的问题及局限性。对目前小批量生产质量控制的方法进行简要分析。在此基础上，提出一种适合于小批量生产质量控制的新思路，并用实际数据对提出的方法与传统的休哈特控制图方法进行了对比，说明这种新思路应用在小批量生产过程中的可行性和有效性。     

面向手工装配的计算机辅助装配过程控制方法

基于手工装配的复杂产品装配过程随机性较大,生产节拍不明显,缺乏有效的技术手段和方法对产品装配过程进行控制.针对这一问题,提出一种新型的面向手工装配的计算机辅助装配过程控制方法,该方法由装配工艺流程图创建、装配信息集成展示与工位数据采集、装配流程控制和装配进度监控三部分组成.引入工作流管理技术,把离散化产品的装配过程控制转化为对产品装配流程的控制,从而实现对复杂产品装配过程的时间进度、技术状态、装配质量的有效控制和基于装配流程的数据统一管理,为解决面向手工装配的复杂产品装配过程控制难的问题提供了有效的途径和方法.     

双星编队构形保持抗干扰容错控制

为解决系统模型误差、外部干扰以及执行器故障引起的双星编队轨道控制精度低、稳定性差问题,设计一种基于观测器的抗干扰容错线性二次型调节器(LQR)控制策略.首先,根据编队双星相对运动动力学模型,设计基于双比例积分自适应律的增广观测器,同时实现对系统状态、间歇故障与快速时变故障、可建模干扰的快速精确估计,并采用H∞优化技术抑...     

数控机床进给伺服系统特性对轮廓误差的影响

文章讨论了进给伺服系统稳态特性对轮廓误差的影响.介绍位置闭环控制模型与跟随误差的基本概念,推导跟随误差与轮廓误差之间的数学描述,分析在加工直线轮廓和圆弧轮廓时跟随误差与轮廓误差之间的关系,以进一步提高零件轮廓的加工精度.     

Analysis of force patterns and tool life in milling operations

The paper describes the practical effects of the operating parameters in the milling operation. Experiments have been conducted to measure cutting force and tool life under dry conditions. Based on the experimental results, three mathematical models have been developed: Force, TLife and Force/TLife. Further analyses have been conducted on the cutting force patterns: seasonal pattern and nonlinear trend. A process optimisation that is based on the minimum production cost has been applied to relate Force model, TLife model and machinability criteria, such as power consumption, cutting parameters and surface roughness.Nomenclature C _w cost of workpiece ($) - C _s set-up cost ($) - C _m machining cost ($) - C _o overhead cost ($) - C _r tool replacement cost ($) - C _t tool cost ($) - D diameter of the cutter (inch) - d depth of cut per pass (inch) - d ₀ required depth (inch) - e _t random error attth sample - F cutting force (N) - f feedrate (ipm) - L length of workpiece (inch) - N spindle speed (r.p.m.) - n number of teeth - P power of the motor (h.p.) - R surface roughness (µm) - R _e real part of a complex function - T tool life (min) - t sample number - t _m machining time (s) - t ₀ overhead time (s) - t _r tool replacement time (s) - t _s set-up time (s) - U _i unit cost of itemi ($/unit)v - v cutting speed (i.p.m.)     

A synthetic control chart for monitoring process dispersion with sample range

A synthetic control chart for monitoring the changes in the standard deviation of a normally distributed process is proposed in this paper. The synthetic chart consists of the sample range (R) chart and the conforming run-length (CRL) chart. The R chart can be viewed as a special case of the synthetic chart. The operation, design and performance of this chart are described. Average run- length comparisons between other procedures and the synthetic chart are presented. It indicates that the synthetic chart is a good alternative for monitoring process dispersion. The variable sampling interval (VSI) schemes, as an enhancement to the synthetic chart, are discussed to further improve the chart performance. An example is presented to illustrate the application of synthetic chart and its VSI scheme.     

Cell formation with alternative process routings and machine reliability consideration

Cell formation is the first step in the design of cellular manufacturing systems. The main objective of this step is to cluster machines and parts into machine cells and part families respectively so that the minimum of intercellular part movements will be achieved. In this paper, we will focus on the configuration of machine cells considering production volumes and process sequences of parts. Also, we will study alternative process routings for part types and machine reliability considerations. A pure linear integer program will be developed to formulate this situation. The results of solving numerical examples show that the reliability consideration has significant impacts on the final block diagonal form of machine-part matrixes.     

Computer-aided process dimensioning

Conventionally, working dimensions have to be given before the construction of a tolerance chart can begin. Because the method of determining the working dimensions is based on trial and error, it is tedious and time-consuming. This paper proposes a method that can generate the working dimensions automatically from the process sequences and the blueprint dimensions. The method uses a relationship matrix to represent the process sequences and a special path-tracing technique to identify the process links. A unique algorithm is developed to reduce the unknown working dimensions to a system of linear equations, which is then solved using the Gauss elimination technique. This method can either be adopted by the process planner or implemented on a microcomputer. With this method, different processing sequences based on different factors, e.g. cost, machining time, etc., can be evaluated efficiently and economically. The developed program is then tested on a practical example.     

Statistical process control using optimized neural networks: A case study

The most common statistical process control (SPC) tools employed for monitoring process changes are control charts. A control chart demonstrates that the process has altered by generating an out-of-control signal. This study investigates the design of an accurate system for the control chart patterns (CCPs) recognition in two aspects. First, an efficient system is introduced that includes two main modules: feature extraction module and classifier module. In the feature extraction module, a proper set of shape features and statistical feature are proposed as the efficient characteristics of the patterns. In the classifier module, several neural networks, such as multilayer perceptron, probabilistic neural network and radial basis function are investigated. Based on an experimental study, the best classifier is chosen in order to recognize the CCPs. Second, a hybrid heuristic recognition system is introduced based on cuckoo optimization algorithm (COA) algorithm to improve the generalization performance of the classifier. The simulation results show that the proposed algorithm has high recognition accuracy.     

基于统计过程控制与维护策略的联合经济设计模型

在已有研究的基础上,对传统的统计过程控制模型进行拓展,融合了设备维护的思想,给出了联合经济模型。该模型考虑了生产过程出现的三种情况,运用控制图监视每种情况的生产状态,通过田口质量损失函数定义相应状态的质量损失成本,并根据过程所处的生产状态对其实施相应的维护策略。过程产生的质量成本与维护成本计入总生产成本,以获得最优的控制图界限系数、抽样检验间隔、实施计划维护前需要的样本数量及样本大小,使得生产过程在生产周期内的总期望生产成本最小。模型结果有助于生产人员根据特定的生产过程情况做出科学经济的生产计划和决策。采用单纯型搜索法对模型进行求解,求解过程通过MATLAB工具箱实现,通过数值例子和参数敏感度分析说明了该模型的有效性。     

Definition and estimation of joint-space contour error based on generalized curve for five-axis contour following control

Five-axis contour following is one of the main tasks for five-axis CNC machine tools. The contour following accuracy directly determines the final machining precision. Therefore, control of the five-axis contour error is significant. Currently, most existing definitions of five-axis contour error are in the Cartesian task space, and this inevitably requires direct and inverse Jacobian transformations between the task-space contour-error computation and the joint-space contour-error control. Different from them, this paper defines the five-axis contour error in the ℝ⁵ joint space through adjusting uniform units of five joints, and accordingly proposes a third-order estimation algorithm for the defined joint-space contour error, with the help of the concept of generalized curve. Based on the joint-space contour-error definition and estimation, a joint-space five-axis cross-coupling control scheme is finally provided. Simulation and experimental results demonstrate that the presented third-order joint-space contour-error estimation algorithm has a satisfactory estimation accuracy, and the presented joint-space five-axis contour control method can decrease both of the joint-space and the task-space five-axis contour errors by more than 49%. It is also analyzed and verified that comparing with routine task-space five-axis contour control method, the presented joint-space method not only needs not the direct and inverse Jacobian transformations during error estimation, which saves the computational burden, but also generates minimum axial contour-control commands, which enhances the control stability, thus resulting in better contour-following performances.