Feature-driven,process-based approach to the integration of CAD /CAM in wireframe models

This paper presents a structure for an integrated CAD/CAM system in wireframe models than can be simultaneously used for product design and manufacture of prismatic components. A feature-driven, process-based design methodology, which derives its basis from traditional geometry-based design, feature-based design, deterministic and expert heuristic manufacturing knowledge, is proposed. This methodology provides an integrated modelling environment for automation of downstream manufacturing applications such as process planning and NC code generation. Representation of features in the design database is not limited to geometry alone but includes material, tooling and machine specifications and is based on a process-to-geometry mapping. Research shows that informational completeness of a CAD database depends on application; and for manufacturing tasks, the vocabulary of the process describing the means of making a part should be mapped directly to the feature-based geometry. This effort answers key issues in integrating CAD and CAM in the most widely used wireframe modelling systems.     

复杂型材智能加工制造系统的设计

目的 实现新一代信息技术背景下传统铝门窗幕墙型材加工行业的转型升级,以应对复杂型材加工制造存在的成本高、工序繁多等诸多挑战。方法 根据型材加工工艺流程及该行业定制化生产的特点,提出一种涵盖网上下单、订单自动处理、机床智能加工生产的复杂型材智能加工制造系统架构,重点针对自主开发的门窗幕墙型材一站式加工智能机床,研发出一套复杂型材智能加工制造系统。结果 研究了加工信息数字化模型、工艺数据库等关键技术。通过工艺数据库的构建,实现了自动编程系统的搭建。结合Web Service与XML技术,研发出订单自助处理系统、机床智能操作管理系统及其与ERP系统的集成互连,打通了生产各环节之间的技术壁垒,形成了复杂型材一体化加工工艺。结论 实际测试表明,经复杂型材智能加工制造系统一体化制造的复杂型材从接受订单到产品加工完成只需40分钟,大幅提高了生产效率和产品质量,降低了加工成本。本研究为复杂型材智能加工及其他传统制造行业的转型升级提供了有益的借鉴和参考。     

Feature-based representation for manufacturing planning

Improved integration using product models in a computer aided design and manufacture environment implies that there is an enhanced need to provide information support across a wide range of applications. In a typical situation concerned with mechanical products, these applications are likely to include detail design, process planning and assembly planning. Features have frequently been used to support these and other applications individually, but single feature representations that simultaneously meet the information needs of a number of applications are unusual. Assembly and process planning are two important aspects of an integrated design and manufacture system, and a formal structure for their representation in a feature-based design system is presented. Features are considered to be machined volumes and are described in a hierarchical taxonomy that is designed to be useful across a range of machined components. The assembly structure is also defined hierarchically with the (machining) features forming the basic entities in the assembly. Assembly relationships among features are defined in the form of mating relationships that are carried by the features. A set of mating relationships between pairs of features has been defined after having studied the literature and a number of engineering products. An integrated data structure containing process planning information from earlier research work and the assembly mating relationships is presented and forms the basis of class definitions for each level in the assembly hierarchy. Object-oriented programming techniques have been used to implement a prototype system using the ACIS solid modelling kernel. The research has illustrated the feasibility of using a single feature representation to support a number of activities within a computer integrated manufacturing environment.     

Structured approach to the design of a production data analysis facility Part 2: Implementation and evaluation

This paper reports research into a novel machining, inspection and analysis facility directed towards a small manufacturing enterprise. A major feature of the facility is the ability to produce rapid manufacturing control through feedback data generated from the seamless integration of machining, inspection and production data analysis activities in order to influence the regeneration of NC part programs. The major contribution of the paper explores the implementation and evaluation of a prototype production data analysis facility that consists of four constituents: machine and inspection planning, production code generation, comparative tolerance analysis, and manufacturing data analysis, the execution of which is supported by the use of order and manufacturing information models. An integrated multifunctional prototype production data analysis software tool has been developed for a limited number of manufacturing features for 2½D prismatic components. This prototype software tool has been tested and is critically reviewed with future work.     

Fixture design information support for integrated design and manufacturing

Although a vast amount of research has been conducted on developing computer-aided fixture design systems, the need for information exchange between the fixture design domain and other manufacturing domains has not been thoroughly dealt with. This paper addresses this gap in fixture design research through the development of appropriate information models for computer-aided fixture design systems to support integrated design and manufacturing. A fixture design activity model is presented that relates fixture design to other design and manufacturing activities. The implementation of the information models in XML and the exchange of the information models based on an XML messaging approach are also discussed.     

A mixed integer goal programming model for discrete values of design requirements in QFD

A main feature of quality function deployment (QFD) planning process is to determine target values for the design requirements (DRs) of a product, with a view to achieving a higher level of overall customer satisfaction. However, in real world applications, values of DRs are often discrete instead of continuous. Therefore, a mixed integer linear programming (MILP) model considering discrete data is suggested. As opposed to the existing literature, the fulfilment levels of DRs are assumed to have a piece-wise linear relationship with cost; because, constraints of technology and resource rarely provides a linear relationship in manufacturing systems. In the proposed MILP model, we considered customer satisfaction as the only goal. But, QFD process may be necessary to optimise cost and technical difficulty goals as well as customer satisfaction. Therefore, by developing the MILP model with multi-objective decision making (MODM) approach, a novel mixed integer goal programming (MIGP) model is proposed to optimise these goals simultaneously. Finally, MILP model solution turns out to be a more realistic approach to real applications because piece-wise linear relationship is taken into account. The solution of MIGP model provided different alternative results to decision makers according to usage of the lexicographic goal programming (LGP) approach. The applicability of the proposed models in practice is demonstrated with a washing machine development problem.     

A CAPP framework with optimized process parameters for rotational components

Process planning, as a critical stage integrating the design and manufacturing phase in a manufacturing environment, has been automated to meet the needs for higher productivity and lower production cost. Being an input to various systems such as scheduling and routing, process planning results are of great importance in the manufacturing stage. Though feature extraction and sequence optimization have been given much attention, the process parameters are rarely dealt with. This paper focuses on the development of a new generative computer aided process planning (CAPP) framework for rotational components. The developed framework includes modules for feature extraction based on CAD application programming interfaces, determination of the optimum sequence and generation of optimum process parameters. The optimization of the machining operations is achieved using the evolutionary technique. The approach resulted in the reduction and prediction of machining time and cost. The framework is demonstrated with a case study.     

The application of STEP-NC using agent-based process planning

Computer aided part programming is an information intensive activity, and provides an interesting area for the application of artificial intelligence, knowledge-based systems and recently for agent technologies. Intelligent software agents can behave and respond autonomously to set criteria. The flexibility of agents and their ability to make autonomous/cooperative decisions makes them an excellent tool in the development of future computer aided process planning systems. In addition, a new ISO standard for NC machine tool programming is emerging called ISO 14649, informally known as STEP-NC. This standard is aimed to replace the existing ISO 6983 (G&M code) standard, which has been in use since the first NC machine tools were developed in the 1950s. STEP-NC does not describe tool movements but uses a higher-level language to define operations known as Workingsteps. A new breed of intelligent controller is envisaged to determine optimized tool trajectories allowing advanced inter-operability and a bi-directional information flow which allows edits made at the machine to be fed back to the CAD/CAM model. This paper presents a STEP-NC compliant computational environment used to demonstrate agent-based process planning, resulting in the generation of STEP-NC code. The system comprises a multi-agent framework, where agents represent the individual features of the component and work independently and cooperatively to generate process plans for discrete component manufacture. This is demonstrated through a series of case study components which evaluate various feature interaction scenarios.     

Optimal inventory costs in a complementary flexible manufacturing system

Flexible manufacturing systems (FMS) have provided job shop-type operations a variety of solutions to their widely documented inefficiencies. FMS come with a wide spectrum of capabilities and are used in a wide variety of manufacturing environments. The present study proposes there are situations where inventory control issues need to be considered during the FMS set-up planning. It has developed a non-linear mathematical programming model, which also has binary variables, to optimize inventory costs during the set-up planning for a sample FMS installation. The solution to the mathematical model is non-trivial. It shows that using this model in conjunction with analytical methods such as constraint propagation and generate-and-test, and sigmoid function approximations, facilitates robust solutions to some of the subproblems of the FMS set-up problem. The study also provides an exchange curve based framework for analysing the implications of inventory policy variables on decisions made at the FMS set-up stage.     

Features extraction with the consideration of manufacturing processes

Computers are being used increasingly in the process planning function. The starting point of this function involves interpreting design data from a CAD model of the designed component. Feature-based technology is becoming an important tool for this. Automatic recognition of features and extraction of feature information from CAD data can be used to drive a process planning system. In this paper a new approach to automatic feature extraction called the 'blank-surface concave-edge' (BS-CE) approach is illustrated. This approach attempts to remove as much of the blank material within a given machine setup as possible. Hence intuitively one can say that the manufacturing cost of material removal may be minimized if this technique is employed. This feature extraction method is explained along with examples of its implementation. An analysis of alternate feature extraction results is performed and the cost of manufacture is compared to demonstrate the near optimal performance of this technique. Then a rule-based technique for feature recognition is presented.     

Fuzzy multiple objective decision making approach to prioritize design requirements in quality function deployment

Quality function deployment (QFD) is a customer-oriented design tool for developing new or improved products to increase customer satisfaction by integrating marketing, design engineering, manufacturing, and other related functions of an organization. QFD focuses on delivering value by taking into account customer needs and then deploying this information throughout the development process. Although QFD aims to maximize customer satisfaction, technology and cost considerations limit the number and the extent of the possible design requirements that can be incorporated into a product. This paper presents a fuzzy multiple objective programming approach that incorporates imprecise and subjective information inherent in the QFD planning process to determine the level of fulfilment of design requirements. Linguistic variables are employed to represent the imprecise design information and the importance degree of each design objective. The fuzzy Delphi method is utilized to achieve the consensus of customers in determining the importance of customer needs. A pencil design example illustrates the application of the multiple objective decision analysis.     

Unified representation of fixtures: clamping,locating and supporting elements in CNC manufacture

A CNC machining operation is the outcome of the application of the integrated capabilities of various resources within the CNC machining centre. Part fixtures, clamping and other location mechanisms are essential subsets of CNC machining resources. Today, various fixturing techniques and attachments available in the market allow manufacturers to enhance their production capability without buying expensive machine tools. This technology-rich fixturing domain is detached while representing and exchanging machine tool resource information for making manufacturing decisions. The research work in this article utilises the STEP-NC compliant unified manufacturing resource model (UMRM) for representing fixtures in conjunction with the parent CNC machining centre. Thus, UMRM is enhanced in this context to represent various fixtures such as universal vises, chucks, pallets and auxiliary rotary tables among others. The major contribution of this article is the application of the extension of the UMRM approach for representing fixturing domain, which allows generic modelling of fixtures and loading devices in addition to machine workpiece and process modelling. This would enable the stage of automated process planning and manufacturing. The universal approach in representing resource information allows the data to be utilised for making a wide variety of manufacturing decisions.     

Cellular manufacturing systems design with routing flexibility,machine procurement,production planning and dynamic system reconfiguration

This paper investigates the problem of designing cellular manufacturing systems with multi-period production planning, dynamic system reconfiguration, operation sequence, duplicate machines, machine capacity and machine procurement. An important aspect of this problem is the introduction of routing flexibility in the system by the formation of alternate contingency process routings in addition to alternate main process routings for all part types. Contingency routings serve as backups so as to effectively address the reality of part process routing disruptions (in the main routings) owing to machine breakdowns and allow the cellular manufacturing system to operate in a continuous manner even in the event of such breakdowns. The paper also provides in-depth discussions on the trade-off between the increased flexibility obtained versus the additional cost to be incurred through the formation of contingency routings for all parts. Some sensitivity analysis is also performed on some of the model parameters. The problem is modelled and solved through a comprehensive mixed integer programming formulation. Computational results presented by solving some numerical examples show that the routing and process flexibilities can be incorporated within the cellular manufacturing system design without significant increase in the system cost.     

Structured approach to the design of a production data analysis facility. Part 1: Conceptual design and information requirements

The paper reports research into a workshop-oriented machine and inspection framework for a contemporary metalworking small manufacturing enterprise (SME) that cannot be satisfactorily achieved by the rigid scaled-down versions of software applications employed within larger companies. It identifies a structured approach to the design and conceptualization of a production data analysis framework that is supported by the use of order and manufacturing data. A major feature of the framework is its generic applicability and totally integrated approach to provide rapid manufacturing control from intelligent feedback data from the inspection and manufacturing data analysis activities of manufactured components. This production data analysis approach is formally expressed through the combined application of both the activity analysis formalism of IDEF0 and object-oriented information analysis methodology of Booch. The systematic approach employed by the integrated production data analysis framework provides both product and manufacturing process control in order to close the manufacturing feedback loop. These integrated phases are described and involve the concurrent machine operation and inspection planning, simultaneous production code generation, comparative tolerance analysis, and manufacturing data analysis of manufactured components. The final part of the paper provides a critical discussion on a number of major issues of the approach and identifies the advantages and limitations of the research.     

The Internet as a tool with application to agile manufacturing: A web-based engineering approach and its implementation issues

This paper presents a novel approach to implementing agile design and manufacturing concepts by using Internet-based technology. The underlying philosophy of the approach is to use web-based design and manufacturing support systems as smart tools from which design and manufacturing customers can rapidly and responsively access the system's built-in design and manufacturing expertise. The approach is described in detail with application examples. The major issues in implementing the approach are discussed with particular reference to using Java programming, client-server technology and open computing of design and manufacturing requirements. The paper concludes with a discussion on the potential of the proposed approach.     

Operations scheduling under electricity time-varying prices

Global climate change requires stakeholders to consider energy elements in their decision-making. Electricity costs, in particular, constitute a significant portion of operational costs in most manufacturing systems. The electricity bills can be lowered if electricity-consuming operations are correctly scheduled. We consider a manufacturing operations control problem with known time-varying electricity prices in a finite planning horizon. Each operation is unique and has its own concave electricity consumption function. Pre-emptions of operations are allowed, yet postponing an operation incurs a cumulative penalty for each time period. In addition, each pre-emption is considered a new operation. The electricity cost in each time period is exogenous and there exists a capacity constraint on the total electricity amount consumed in each period due to infrastructure and provider’s limitations. There is a fixed start-up cost incurred for switching on the machine and a fixed reservation cost incurred for keeping the machine ‘On’. The system also includes a rechargeable battery. The customer has to determine when to process each operation within the time horizon so as to minimise total electricity consumption and operations postponement penalty costs. A dynamic programming solution is proposed and the complexity of the models is analysed. After examining several special cases of the model, the optimum times to charge and discharge the rechargeable battery are determined. A polynomial time algorithm for a special case of a single operation with uniform capacity is proposed.     

计算机辅助装配规划研究综述

装配规划是影响产品装配质量和成本的重要因素,作为并行工程和计算机集成制造的关键支撑技术,计算机辅助装配规划涉及计算机、人工智能、自动化和机器人等领域。对目前该领域国内外的研究现状进行了综述,总结和剖析了经典方法、虚拟现实方法、软计算方法和协同方法等4 种具有代表性的装配规划技术,并对今后计算机辅助装配规划的发展方向和研究趋势进行了分析。     

Fuzzy goal-programming model with an artificial immune system (AIS) approach for a machine tool selection and operation allocation problem in a flexible manufacturing system

Some of the important planning problems that need realistic modelling and a quicker solution, especially in automated manufacturing systems, have recently assumed greater significance. In real-life industrial applications, the existing models considering deterministic situations fail as the true language adopted by foremen and technicians are fuzzy in nature. Thus, to map the situation on the shop floor to arrive at a real-time solution of this kind of tactical planning problem, it is essential to adopt fuzzy-based multi-objective goals so as to express the target desired by the management of business enterprises. This paper presents a fuzzy goal-programming approach to model the machine tool selection and operation allocation problem of flexible manufacturing systems. The model is optimized using an approach based on artificial immune systems and the results of the computational experiments are reported.     

Making IT fit: the design of integrated manufacturing systems

One of the important implications of information technology (IT) is that it has made possible widespread automation in manufacturing industry. However, the bulk of this has involved discrete automation of single plant items or process elements rather than the total production system. Although the capital cost of such total system automation is a significant factor in slowing the rate of change in this direction, there are also a number of problem issues related to the integration of machines, computers and human systems within manufacture and design. Arguably the types of issue involved are not fully understood and in many cases the technological change is demanding totally new approaches and responses to the design of production systems and the traditional manufacture/design connections.The paper explores some of the issues raised in advanced manufacturing systems, drawing on case study research into the adoption of flexible manufacturing systems as an example of computer-integrated manufacture. It comments on the experience of case study firms and presents some comments on the design problems facing those responsible for integrated manufacturing systems.     

A mixed-integer programming approach to the machine loading and process planning problem in a process layout environment

A mixed-integer programming (MIP) model for the machine loading and process planning problem has been developed for a process layout environment. This model relaxes the most commonly used assumption that each operation can be assigned to only one machine. In this model, the most important production cost components: machining cost, material handling (MH) cost, setup cost and machine idle cost are considered. In addition, by assigning penalty cost for long makespans, the optimal process routes for each part and optimal load for each machine in terms of minimum production cost can be obtained with lower makespan. An example problem is solved, followed by discussions with regard to the impact of batch splitting, setup cost and demand change on optimal solution.