Design of a reconfigurable prognostics platform for machine tools

For decades, researchers and practitioners have been trying to develop and deploy prognostics technologies with ad hoc and trial-and-error approaches. These efforts have resulted in limited success, due to the fact that it lacks a systematic approach and platform in deploying the right prognostics tools for the right applications. This paper introduces a methodology for designing a reconfigurable prognostics platform (RPP) which can be easily and effectively used to assess and predict the performance of machine tools. RPP can be installed on the equipment and it has the prognostic capabilities to convert the data into performance-related information. The equipment performance information can then be integrated into the enterprise asset management system for maintenance decision making through the Internet. Two industrial cases are used to validate the effectiveness of applying the RPP for different prognostic applications as well as the reconfigurable capabilities of the proposed RPP.     

Design of a STEP compliant system for turning operations

The changing economic climate has made global manufacturing a growing necessity over the last decade, forcing companies from East and West to collaborate beyond geographic boundaries in the design, manufacture and assembly of products. The ISO 10303 and ISO 14649 Standards (STEP and STEP-NC) have been developed to introduce interoperability into manufacturing enterprises so as to meet the challenges of responding to production on demand. This paper describes and illustrates a STEP compliant CAD/CAPP/CAM System for the manufacture of rotational parts on CNC turning centers. The information models to support the proposed system together with the data models defined in the ISO 14649 standard used to create the NC programs are also described. A structured view of a STEP compliant CAD/CAPP/CAM system framework supporting the next generation of intelligent CNC controllers for turn/mill component manufacture is provided. Finally a proposed computational environment for a STEP-NC compliant system for turning operations (SCSTO) is described. SCSTO is the experimental aspect of the research and is supported by information models that and have been constructed using a structured methodology and object-oriented methods. SCSTO was developed to generate a Part 21 file based on machining features to support the interactive generation of process plans utilizing feature extraction. A case study component has been developed to prove the concept of using the milling and turning parts of ISO 14649 to provide a turn-mill CAD/CAPP/CAM environment.     

A novel methodology to measure the responsiveness of RMTs in reconfigurable manufacturing system

Reconfigurable manufacturing systems are designed to deliver exact functionality and capacity that is needed, when it is needed. The reconfigurable machine tool (RMT) plays a pivotal role in the accomplishment of this objective through their built in modular structure consisting of basic and auxiliary modules along with the open architecture software.     

Selection of an optimal set of cutting-tool sizes for 21/2D pocket machining

The availability of high speed automatic tool change mechanisms in modem CNC machining centers is making it practical to consider the use of multiple cutting-tool (specifically, flat end-mill) sizes to reduce the total time for machining a 21/2D) pocket. However, current CAD/CAM systems do not support pocket machining using multiple cutting-tool sizes. In this paper, we describe a two-phase methodology for selecting an optimal set of cutting-tool sizes to machine a 21/2D pocket. In the first phase, we employ a new concept called the Voronoi mountain in order to calculate the material volume that can be removed by a specific cutting-tool size, the material volume that will subsequently remain to be machined, and the cutter-paths (and corresponding processing times) for each cutting-tool. In the second phase, we apply a dynamic programming approach for optimal selection of cutting-tool sizes on the basis of the processing time. Our computational experiments indicate that substantial savings in processing time can be achieved by using multiple cutting-tool sizes to machine 21/2D pockets.     

Material side tracing and curve refinement for pencil-cut machining of complex polyhedral models

In this paper, a new Material-Side-Tracing method and a pencil-cut curve refinement technique are proposed for 3-axis pencil-cut path generation. Pencil-cut machining has been used to remove remaining material at highly curved regions or corners after the finishing process. Procedures of evaluating and extracting valid pencil-cut points are developed by taking practical cases into account. With the strategy of using material-side information in the tracing process, smooth and clean pencil-cut curves can be generated even if the actual adjacent pencil-cut curves are very close. A technique of pencil-cut curve refinement is presented to overcome the limitation due to the discrete CL-net intervals, and the smooth pencil-cut paths are made complete at sharp corners. Computer implementation and practical examples are also presented in this paper. The proposed techniques can be used in the CAD/CAM systems to generate pencil-cut paths for machining complex polyhedral models.     

Optimizing tool orientations for 5-axis machining by configuration-space search method

This paper presents a methodology and algorithms of optimizing and smoothing the tool orientation control for 5-axis sculptured surface machining. A searching method in the machining configuration space (C-space) is proposed to find the optimal tool orientation by considering the local gouging, rear gouging and global tool collision in machining. Based on the machined surface error analysis, a boundary search method is developed first to find a set of feasible tool orientations in the C-space to eliminate gouging and collision. By using the minimum cusp height as the objective function, we first determine the locally optimal tool orientation in the C-space to minimize the machined surface error. Considering the adjacent part geometry and the alternative feasible tool orientations in the C-space, tool orientations are then globally optimized and smoothed to minimize the dramatic change of tool orientation during machining. The developed method can be used to automate the planning and programming of tool path generation for high performance 5-axis sculptured surface machining. Computer implementation and examples are also provided in the paper.     

FPGA-based hardware CNC interpolator of Bezier,splines, B-splines and NURBS curves for industrial applications

Tool path interpolation is an important part of Computerized Numerical Control (CNC) systems because it is related to the machining accuracy, tool-motion smoothness and overall efficiency. The use of parametric curves to generate tool-motion trajectories on a workpiece for high accuracy machining has become a standard data format that is used for CAD/CAM (Computer Aided Design/Computer Aided Manufacturing) and CNC systems. Splines, Bezier, B-splines, and NURBS (Non-Uniform Rational B-splines) curves are the common parametric technique used for tool path design. However, the reported works bring out the high computational load required for this type of interpolation, and then at best only one interpolation algorithm is implemented. The contribution of this paper is the development of a hardware processing unit based on Field Programmable Gate Arrays (FPGA) for industrial CNC machines, which is capable of implementing the four main interpolation techniques. It allows the selection of the required interpolation technique according the application. Two CAD models are designed for test the CNC interpolations; experimental results show the efficiency of the proposed methodology.     

Automated surface subdivision and tool path generation for -axis CNC machining of sculptured parts

As an innovative and cost-effective method for carrying out multiple-axis CNC machining, -axis CNC machining technique adds an automatic indexing/rotary table with two additional discrete rotations to a regular 3-axis CNC machine, to improve its ability and efficiency for machining complex sculptured parts. In this work, a new tool path generation method to automatically subdivide a complex sculptured surface into a number of easy-to-machine surface patches; identify the favorable machining set-up/orientation for each patch; and generate effective 3-axis CNC tool paths for each patch is introduced. The method and its advantages are illustrated using an example of sculptured surface machining. The work contributes to automated multiple-axis CNC tool path generation for sculptured part machining and forms a foundation for further research.     

分布式协同设计技术综述

分析了分布式协同设计中的关键技术问题,介绍了其目前的主要研究进展和代表性成果．在集成技术方面,重点阐述了CAX／DFX工具的分布集成问题,包括封装、互操作、本体论;在协同技术方面,集中分析了异步协同设计、同步协同设计和协同装配设计;最后对该领域需要解决的深层次问题进行了讨论。     

机械产品并发设计原理与方法的探讨

一、前言 为使计算机在机械设计应用中充分发挥作用,创造出一种能模拟人类专家群对杂产品设计问题进行并行处理、相互合作这一自然属性的软件环境是+分重要的。并发设计Concurrent Design),作为     

快速成型技术及其在产品设计中的应用

本文介绍了快速成型技术(Rapid Prototyping)的原理,重点讨论了快速成型方法,提出快速成型技术在产品概念设计评价、设计验证以及快速模具设计中的重要应用,强调应用快速成型技术提高设计质量。     

计算机辅助设计在工业设计的应用状况及发展前景

在工业设计进行的流程中,计算机辅助设计悄然的穿插在每一个相对独立的主题活动之中.从一个完整的设计流程审视,计算机辅助设计的作用显而易见.它在设计流程数据管理,产品效果表现以及计算机辅助模型制作等广泛应用,发挥了工具化的作用.在应用过程中,促进了其自身的发展和工业设计的发展.     

Drilling reconfigurable machine tool selection and process parameters optimization as a function of product demand

Special purpose machines (SPMs) are customized machine tools that perform specific machining operations in a variety of production contexts, including drilling-related operations. This research investigates the effect of optimal process parameters and SPM configuration on the machine tool selection problem versus product demand changes. A review of previous studies suggests that the application of optimization in the feasibility analysis stage of machine tool selection has received less attention by researchers. In this study, a simulated model using genetic algorithm is proposed to find the optimal process parameters and machine tool configuration. During the decision-making phase of machine tool selection, unit profit is targeted as high as possible and is given by the value of the following variables: SPM configuration selection, machining unit assignment to each operation group, and feed and cutting speed of all operations. The newly developed model generates any random chromosome characterized by feasible values for process parameters. Having shown how the problem is formulated, the research presents a case study which exemplifies the operation of the proposed model. The results show that the optimization results can provide critical information for making logical, accurate, and reliable decisions when selecting SPMs.     

加工特征识别系统ZD-AFRS及其健壮性增强方法

介绍了混合特征识别系统ZD－AFRS的设计思想、系统结构、核心功能的设计与实现，以及增强系统健壮性的方法。以先进性与实用性并重为原则，在ZD－AFRS的研制过程中，通过设计可靠的分割面处理、合并面处理和虚链生成算法，提高系统自动特征识别功能的健壮性；通过将交互特征定义与自动特征识别进行有机集成，提高系统的容错性；通过提供用户自定义特征功能使系统具有可扩展性；通过开发体特征生成、合理特征解释生成和先坯自动生成等功能使系统的功能更完善。经过较多的测试表明，ZD－AFRS具有较好的健壮性和实用性。     

Analysis and correction of the machining errors of small plastic helical gears by ball-end milling

Many small-size precise plastic helical involutes gears are used in electrical appliances to transmit rotary movements continuously and smoothly.Ball-end milling is an effective method for trial manufacture or small batch production of this type of gear,but the precision of the gear is usually low.In this research,the main sources of the errors of the gear,machining errors of the tooth profile and trace of the gear obtained were analyzed.The correction amounts for these errors are then determined by using a CNC gear tester.They are used to generate a new 3D-CAD model for gear machining with better precision.     

Towards a generic design method for reconfigurable manufacturing systems: Analysis and synthesis of current design methods and evaluation of supportive tools

In today’s global manufacturing environment, changes are inevitable and something that every manufacturer must respond to and take advantage of, whether it is in regards to technology changes, product changes, or changes in the manufacturing processes. The reconfigurable manufacturing system (RMS) meets this challenge through the ability to rapidly and efficiently change capacity and functionality, which is the reason why it has been widely labelled the manufacturing paradigm of the future. However, design of the RMS represents a significant challenge compared to the design of traditional manufacturing systems, as it should be designed for efficient production of multiple variants, as well as multiple product generations over its lifetime. Thus, critical decisions regarding the degree of scalability and convertibility of the system must be considered in the design phase, which affects the abilities to reconfigure the system in accordance with changes during its operating lifetime. However, in current research it is indicated that conventional manufacturing system design methods do not support the design of an RMS and that a systematic RMS design method is lacking, despite the fact that numerous contributions exist. Moreover, there is currently only limited evidence for the breakthrough of reconfigurability in industry. Therefore, the research presented in this paper aims at synthesizing current contributions into a generic method for RMS design. Initially, currently available design methods for RMS are reviewed, in terms of classifying and comparing their content, structure, and scope, which leads to a synthesis of the reviewed methods into a generic design method. In continuation of this, the paper includes a discussion of practical implications related to carrying out the design, including an identification of potential challenges and an assessment of which tools that can be applied to support the design. Conclusively, further areas for research are indicated, which provides valuable knowledge of how to develop and realize the benefits of reconfigurability in industry.     

面向网络基于分治策略的加工特征识别算法

提出一种面向网络,基于分治的加工特征识别算法,首先将零件剖分成若干个适当大小的分解体;然后对每一分解体进行加工特征识别;最后通过对相关分解体的识别结果进行合并生成零件的加工特征模型,实验结果证实了文中算法的有效性。     

分布式同步协同包装纸盒CAD/CAM系统的设计与实现

采用Java技术开发了基于Web的分布式同步协同包装纸盒CAD／CAM系统．研究了纸盒CAD／CAM系统的体系结构、系统功能的分配、分布式同步协同设计、并发控制、协同感知、负载均衡、3D可视化技术、参数化设计以及系统安全性的保证等关键技术．     

Toolpath generation along directions of maximum kinematic performance; a first cut at machine-optimal paths

In earlier work, we introduced the concept of time-optimal toolpaths, modeled the behavior and constraints of machining, and formulated the optimization problem mathematically. The question was by what toolpath it would be possible to machine a surface in minimum time—while considering the kinematic performance of a machine, the speed limits of the motors and the surface finish requirements. The time-optimal problem is a difficult one, and does not generally yield a closed-form solution. Here we present a heuristics-based approach to the problem, which we refer to as the greedy approach. The performance envelope of the machine at a point on the surface is very anisotropic, and material can be removed much more rapidly in some directions than in other directions. The greedy approach seeks the directions of the best performance. We describe algorithms to first find such advantageous directions. We then show how they can be fitted by a continuous vector field. We also show how toolpaths with the proper side-steps can be generated from this field. We end with results showing the improvement of performance that can be derived from greedy toolpaths.     

支持实体数控铣削仿真验证的Cuboid-Array模型的研究

研究了Z-Buffer,Dexel和Ray-representation建模思想和方法,提出Cuboid-array的实体近似建模方法．采用基于设计模型的实体数控仿真验证技术,以Cuboid-array表示干涉元素集合体,提出基于B-rep和Cuboid-array的双体建模的近似实体数控仿真验证技术．给出了基于Cuboid-array的数控仿真验证算法,研制了基于双体建模和双体显示的数控仿真验证实验系统,实现了面向过程和结果的实体数控仿真的集成、面向实体数控仿真和实体数控验证的集成,并给出了实验用例．