Development of a computer-integrated system to support CAD to CAPP

During the 1990s, Computer-Aided Design (CAD) and Computer-Aided Process Planning (CAPP) have emerged as effective means of improving productivity and efficiency, resulting in widespread research work related to CAD and CAPP integration in the hope of achieving seamless data flow among the relevant computer systems. Unfortunately, the efficiency of process planning systems still needs significant improvement due to the problems of design data loss or design data mis-interpretation. This paper attempts to introduce an intelligent computer-integrated system for reliable design feature recognition in order to achieve automatic process planning. Moreover, it describes a rule-based computer-integrated system for recognizing features of components stored as STEP format, analyzing the design files and designing manufacturing processes. In this approach, the STEP design file is used as the information source for generating detailed manufacturing process. The significance of this research is that the product designs with dissimilar formats from various CAD systems can now be interconnected and automatically coded for multiple manufacturing purposes. It presents an effective method that rule-based reasoning is used to create optimal process plans for metal cutting.     

Computer-aided process planning for NC tool path generation of complex shoe molds

This paper presents a computer aided process planning (CAPP) system for numerical control tool path generation of complex shoe molds. This CAPP system includes both the automation of auxiliary boundary curve generation and machining strategies. The automation of auxiliary boundary curve generation and machining strategies make tool path generation more accurately and efficiently. Traditional shoe mold making is a very tedious process. Even with the utilization of computer-aided design and computer-aided manufacturing (CAD/CAM), the CAM process requires long hours of tool path programming and debugging. It would also take a long time to calculate (sometimes several hours) the tool path for complex athletic footwear. In order to reduce the tool path editing and programming time, this paper proposes the use of CAPP to reduce processing time and increase efficiency. It is difficult, if not impossible, to develop a generic CAPP system that can generate a process plan to solve general production problems. However, it is quite possible to capture the domain knowledge of a certain production process and embed that knowledge into a CAPP system. We prove, by using such a system, that a very complicated process planning problem can be overcome by a knowledge-based CAPP approach. With such an approach, the traditional manufacturing process of shoe molds can be converted to an automatic manufacturing process with the CAPP system. In fact, shoe molds for real production have been created using the developed CAPP system, demonstrating the effectiveness of this approach. In this paper, we show that several complex and different shoe molds and their machining strategies were automatically planned by the proposed CAPP system. The result of a comparison between the CAPP system with the traditional approach is presented and discussed.     

Extraction of machining features for CAD/CAM integration

Feature-based CAD/CAM integration is a technology used to realise automatic transmission and conversion of component information among CAD, CAPP and CAM applications. A feature is the medium of information transmission in the integration. Since a process planning downstream application has a different viewpoint from the component designer, feature conversion or feature extraction methodology is used to create a machining feature model based on the design feature model. One of the major difficulties in generating machining features is the preservation of feature integrity because of feature interactivity. The most current research, therefore, focuses on the planar-type form feature conversion. This paper discusses the problem of feature interactivity and proposes a feature-based approach to generating hole-series machining features from a design feature model. Hole-series features are important machining features for gearbox components used in machine tools. These kinds of features cannot be obtained directly from a design feature database. A constraint-based method is developed in this paper to define a hole-series feature model based on the geometric and topological information extracted from the design database. In addition, a STEP file is generated to interface the converted machining feature model with the downstream CAPP application. The implemented feature conversion system is verified by considering its application to some component examples and the developed prototype CAPP system. This revised version was published online in October 2004 with a correction to the issue number.     

Java-based computer-aided process planning

This investigation addresses distributed environments for computer-aided process planning (CAPP) over a network. The Java 2 Enterprise Edition (J2EE) standard using Java is applied to implement cross-platform and distributed computing architecture, thus reducing the system loading during manufacturing process planning. The product-oriented standard, standard exchange of product (STEP), model data is applied to define a robust data model that associates product, shape, and feature definitions and provides the mechanisms for data exchange, sharing, and integration with other engineering systems, such as computer-aided design (CAD) and computer-aided manufacturing (CAM). STEP AP224 is engaged to define the machining features of machined products in the proposed CAPP system. The life cycle of a product from design to sale, and especially the period of manufacturing, can be greatly shortened; the cost of manufacturing can be reduced and the quality of the product can be improved using the proposed CAPP system.     

基于切削逻辑的结构件数控编程工艺规划

针对结构件数控铣削编程的工艺选择的复杂性,提出了基于切削逻辑的结构件数控编程工艺规划方法。首先,在结构件STEP特征识别的基础上建立了特征工艺模型,而后利用实例检索和基于切削逻辑的规则识别方法进行工艺设计,最后通过实例验证了方法的可行性。     

基于属性邻接图的轴类零件制造特征识别方法

CAD系统与CAPP系统的集成是企业内部各种应用系统集成的基础,制造特征的识别是实现CAD/CAPP集成的关键技术。本文应用基于属性邻接图的方法在AC IS平台上对轴类零件的制造特征进行识别,有效地识别出该类零件的主特征和常见的辅助特征,并利用AC IS提供的类库提取模型底层的几何参数,从而得到定义各项特征所需的几何尺寸信息。最后以XML中性文件的形式输出识别结果,为后续进行的工艺自动生成提供初始数据。     

面向STEP-NC的特征CAD/CAPP系统

将特征建模技术与STEP及STEP-NC标准相结合,为实现CAD/CAPP/CAM及CNC的集成,探索了一条有效的途径。建立基于STEP AP224的特征模型,它包含工艺设计所需要的产品管理、材料、精度等信息。另外,将特征与加工方法链相对应,并建立相应的数据库,同时讨论了工步排序的若干规则。在Pro/ENGINEER软件平台上,实现了CAD/CAPP/CAM高层次的集成。以三轴数控加工的棱柱体零件为例,阐述了工步的产生以及排序,最终生成符合STEP-NC标准的加工文件。     

智能化电火花加工CAPP系统的研究

针对电火花加工工艺的特点,采用专家系统与人工神经网络相给合实现电火花加工智能化CAPP系统——I-EDM-CAPP系统。建立了基于规则的简易Petri网SPN模型以实现加工方法的智能选取;采用复合神经网络（CNN）实现电参数学习模型,从而能够准确地选择并合理地扩展电加工工艺参数。     

A Generative Computer-Aided Process Planning System for Prismatic Components

This paper deals with design and development of a generative computer-aided process planning (CAPP) system for prismatic components and named PSG-CAPP. The proposed CAPP system has been divided into three modules. The first module is concerned with feature extraction. The second and third modules deal with planning the set-up, machine selection, cutting tool selection, cutting parameter selection, and generation of process plan sheet. The whole CAPP system is developed using Visual Basic 6.0 as front end and Oracle 7.3 as back end. The SolidWorks98 plus has been used for modelling, and feature extraction has been implemented using a program written in Visual Basic 6.0. The speciality of the developed CAPP system is that it is linked with the CAD module and it extracts the majority of features automatically prior to process planning. The developed CAPP system has been tested with aerospace components. The main feature of the proposed CAPP system is its ability to handle a variety of prismatic components and generate process plans for them. A case study has been included to highlight the potential of the CAPP system. ID="A1"Correspondance and offprint requests to: Professor P. V. Mohanram, Department of Mechanical Engineering, PSG College of Technology, Peelamedu, Coimbatore 641004, India. E-mail: msadaiah@yahoo.com     

On-line integration of a process planning module with production scheduling

An approach to the on-line integration of process planning and production scheduling is reported. Based on a geometric modeller, a geometric analyser and a knowledge base, the process planner generates alternative process plans and provides automatic tool selection and calculation of the appropriate machining parameters. Time and cost estimations are input to the decision-making module in the production scheduling system that produces optimal scheduling decisions as well as a complete record of the actual state of the factory resources. An information flow, designed as a relational data model, maintains the interaction between the process planning and the production scheduling systems and provides the dynamic feedback to the process planner. Specific geometry features of the blank, the finished part and the cutting tools, and geometry features-based rules are stored in the database of a developed CAPP system by using a separate CAD interface. The integrated production planning and production scheduling system and the CAPP system were validated with rotational parts machining.     

Rule-based process planning by grouping features

A macro-level CAPP system is proposed to plan the complicated mechanical prismatic parts efficiently. The system creates the efficient machining sequence of the features in a part by analyzing the feature information. Because the planning with the individual features is very complicated, feature groups are formed for effective planning using the nested relations of the features of a part, and special feature groups are determined for sequencing. The process plan is generated based on the sequences of the feature groups and features. When multiple machines are required, efficient machine assignment is performed. A series of heuristic rules are developed to accomplish it.     

Integrated setup planning and operation sequencing (ISOS) using genetic algorithm

Process planning is an essential component for linking design and manufacturing process. Setup planning and operation sequencing are two most important functions in the implementation of CAD/CAPP/CAM integration. Many researches solved these two problems separately. Considering the fact that the two functions are complementary, it is necessary to integrate them more tightly so that performance of a manufacturing system can be improved economically and competitively. This paper presents a generative system and genetic algorithm (GA) approach to process plan the given part. The proposed approach and optimization methodology analysis constraints such as TAD?(tool?approach?direction), tolerance relation between features and feature precedence relations to generate all possible setups and operations using workshop resource database. Tolerance relation analysis has a significant impact in setup planning for obtaining the part accuracy. Based on technological constraints, the GA algorithm approach, which adopts the feature-based representation, simultaneously optimizes the setup plan and sequence of operations using cost indices. Case studies show that the developed system can generate satisfactory results in optimizing the integrated setup planning and operation sequencing in feasible condition.     

面向CAD/CAPP集成的特征造型技术研究

介绍了以ＡｕｔｏＣＡＤ１３为支撑环境,用ＶＣ＋＋二次开发出面向ＣＡＤ／ＣＡＰＰ集成的特征造型系统。该系统综合应用了面向制造的特征设计和特征识别技术,采用ＳＴＥＰ标准建立统一的数据模型,便于ＣＡＤ与后续过程的信息集成与并行运行。     

GA-based synthesis approach for machining scheme selection and operation sequencing optimization for prismatic parts

To obtain global and near-global optimal process plans based on the combinations of different machining schemes selected from each feature, a genetic algorithm-based synthesis approach for machining scheme selection and operation sequencing optimization is proposed. The memberships derived from the fuzzy logic neural network (FL-NN), which contains the membership function of each machining operation to batch size, are presented to determine the priorities of alternative machining operations for each feature. After all alternative machining schemes for each feature are generated, their memberships are obtained by calculation. The proposed approach contains the outer iteration and nested genetic algorithm (GA). In an outer iteration, one machining scheme for each feature is selected by using the roulette wheel approach or highest membership approach in terms of its membership first, and then the corresponding operation precedence constraints are generated automatically. These constraints, which can be modified freely in different outer iterations, are then used in a constraints adjustment algorithm to ensure the feasibility of process plan candidates generated in GA. After that, GA obtains an optimal process plan candidate. At last, the global and near-global optimal process plans are obtained by comparing the optimal process plan candidates in the whole outer iteration. The proposed approach is experimentally validated through a case study.     

基于混合智能的电火花成型加工CAPP系统的研究

基于对电火花加工工艺的分析,构造了电火花加工CAPP系统的整体结构模型;该模型采用电极的自动分割和重组的办法实现以简单电极加工复杂型腔,从而降低加工费用;利用基于简易Petri网模型的工程规程智能决策系统实现工艺决策;采用混合智能的方法实现电规准的智能选择,并采用“优先级别－权系数法”建立多目标规划模型实现对工艺过程的优化。     

集成环境下特征基工艺过程设计系统

介绍集成环境下的飞机结构件数控加工的工艺过程设计系统ＦＡ－ＣＡＰＰ，包括ＦＡ－ＣＡＰＰ系统同ＣＡＤ、ＣＡＭ系统的集成，层次化零件特征模型，工艺设计专家系统，系统的结构等。     

CAPP的刀具自动选择系统

提出了一种工艺特征建模和刀具建模的方法 ,给出了CAPP刀具系统的总体结构。描述了基于工艺和刀具定义的刀具选择的一般过程 ,并在此基础上 ,实现了工艺流程和工序内容的参数化分类 ,实现了刀具的自动选择     

基于XML的工艺文件汉英翻译研究

经济全球化要求CAPP支持远程设计和产品数据共享,传统的CAPP系统只支持本地设计,生成的工艺文件是单一语言的,通用翻译软件又不能直接被CAPP系统所使用,因此对开发基于B/S结构的工艺设计和计算机辅助翻译软件提出需求.在分析了工艺语言特点的基础上,为提高基于网络的工艺语言翻译品质,提出利用XML文档进行工艺文件的结构化信息表示和信息的传递与交换,最后对机械加工工序卡的XML结构化表示做了详细说明.     

Automated Process Planning for the Manufacture of Lifters

This paper presents the methodology of a computer-aided process planning system IMOLD  FCAPP for the manufacture of injection moulded components, which will facilitate the standardisation of process planning and significantly reduce lead-time. The main components of the mould such as the slider, the lifter and the mould base are considered in this system. In this paper, the automated process planning for the manufacture of a lifter is described. A combination of the generative and variant approach (hybrid approach) is used for the development of the system. The input to the system is a 3D lifter model. First, the system classifies the lifter types and extracts the feature parameters from the model. Each lifter type refers to a standard process plan template, in which a set of processes is presented in sequence. Secondly, the system selects the machines, cutters, fixtures, and cutting parameters for each process in the plan template, based on the actual dimensions of the features and constraints and rules defined in the system and the available machining resources. The process plan execution is then simulated on the screen step by step.     

Neutral representation of tolerance information for process planning using STEP AP 224

The focus of CIM is on information as it is the crucial element for integrating all the manufacturing activities. CAPP, as one of the key elements in CIM, needs to extract the manufacturing information such as machining features and precision specifications like surface roughness and tolerances from a geometric model in order to link CAD and CAM. However, these data are not real attributes of the geometric model in most of the current CAD systems. Therefore, human interpretation is inevitable for further processing of CAD model for downstream application like process planning or inspection. This paper proposes a scheme to represent the manufacturing information in a neutral format using STEP technology in order to enable downstream users such as process planner and inspection planner to make correct decisions on process selection, processing conditions, etc. It is shown that by using STEP AP224 manufacturing information encompassing machining features, surface roughness, dimensional and geometric tolerances can be completely represented together with part geometry, which certainly contributes to successful implementation of CIM.