Computer-aided design for manufacturing process selection

This paper describes an expert system that helps designers select a manufacturing process in the early stage of product design. First, the paper focuses on net-shape manufacturing processes and identifies the major factors that affect the selection of an appropriate process. Examples of these factors include shape, production volume and material. A versatile methodology should consider all the factors simultaneously in assessing the suitability of the candidate processes. The proposed system uses the concept of design compatibility analysis to represent the suitability of candidate processes with respect to the given product specifications. The system uses this knowledge to eliminate incompatible candidates and rank the compatible set of processes. A prototype system called DFPS uses HyperCard and Prolog to implement the proposed methodology. DFPS also contains information related to each process.     

Prospects for process selection using artificial intelligence

On problem facing modern industry is the lack of a skilled labor force to produce machined parts as has been done in the past. In the near future, this problem may become acute for a number of manufacturing tasks. One such task is process planning. Since process planning requires intelligent reasoning and considerable experiential knowledge, almost all existing computer aided process planning systems require a significant amount of supervision by an experienced human being.There is some prospect that “expert computer system” techniques from the field of Artificial Intelligence may be successfully used to automate (at least partially) several of the reasoning activities involved with process planning. This paper discusses some current prospects for automating a process planning task known as process selection. These ideas are currently being considered for use int he Automated Manufacturing Research Facility project at the U.S. National Bureau of Standards, and steps are being taken to implement them in an expert computer system.     

Process selection for the design of aluminum components

This paper describes a method for process selection of aluminum components in the early stages of design. Aluminum has many advantages in a variety of applications in its manufacturability and recyclability. Yet, engineers who are trained to design steel components do not take full advantage of this material. The main reason is that engineers tend to be unaware of the many economical processing methods for aluminum. We have developed a program that combines preliminary screening of processes with normalized cost analysis. Design compatibility analysis (DCA) ranks each process based on its feasibility with the basic geometry, material, and production requirements. For top candidates, the program employs external cost routines for detailed comparisons. The primary processes considered are extrusion, sheet forming, forging, die casting, and sand casting. The program extends its compatibility and cost analysis to secondary operations such as bending and machining. The program should be useful for engineer training and as a preliminary design tool. The program uses HyperCard as a front-end, Prolog for logic-based analysis, and Excel for cost calculations.     

A decision support system for material and manufacturing process selection

The material and manufacturing process selection problem is a multi-attribute decision-making problem. These decisions are made during the preliminary design stages in an environment characterized by imprecise and uncertain requirements, parameters, and relationships. Material and process selection decisions must occur before design for manufacturing can begin. This paper describes a prototype material and manufacturing process selection system called MAMPS that integrates a formal multi-attribute decision model with a relational database. The decision model enables the representation of the designer's preferences over the decision factors. A compatibility rating between the product profile requirements and the alternatives stored in the database for each decision criteria is generated using possibility theory. The vector of compatibility ratings are aggregated into a single rating of that alternative's compatibility. A ranked set of compatible material and manufacturing process alternatives is output by the system. This approach has advantages over existing systems that either do not have a decision module or are not integrated with a database.     

CAD for process plants: an update

We review the availability of CAD software for the process design activities of physical properties generation, unit operation design, flowsheeting and dynamic flowsheet simulation. Similarly we look at CAD software for materials control, piping documentation and pipe stressing. We report conclusions drawn from our research into the provision and use of CAD turnkey systems for producing schematics at the conceptual design phase, and for equipment specification, layout, piping design and 3D modelling at the engineering design phase.By reviewing the shortcomings of current CAD systems along with developing CAD technology, we were able to specify the requirements of the next generation of process plant CAD.     

关系数据库技术在计算机网络设计中的运用

随着我国社会经济建设水平的不断提高和计算机网络技术的推广普及,关系数据库技术在计算机网络设计中的运用成为社会各领域关注的焦点,本文将从关系数据库技术的角度出发,结合计算机网络设计的实际,对关系数据库技术在计算机网络设计中的运用进行深入的研究和探讨。     

A process model for interactive systems

Designing user interfaces and designing computational software are very different processes. The differences lead to late discovery of design conflicts, which drives up development costs. A unifying methodology that could provide early discovery and resolution of design conflicts must account for the governing principles of both processes. Disciplined long-term investigation of candidate methodologies requires that these governing principles be fixed and that evolving development methods comprising each process be accommodated. This article describes an application of general systems theory to integrate these principles, proposes a process model that fixes them as explicit elements of a process program, argues the feasibility of the model and its worthiness for further study, and describes its initial implementation.     

A distributed expert control system for a hydrometallurgical zinc process

A distributed expert control system (DECSHZ) has been built for a hydrometallurgical zinc process, whose basic steps are leaching, purification and electrolysis. It consists of a central computer management system and three local expert control systems, one for each of the basic steps. This paper deals with the design and application of DECSHZ, especially its distributed architecture and main functions; expert control strategies based on rule models and a combination of rule models and steady-state mathematical models; system implementation; and the results of actual runs. DECSHZ has been found to provide not only a very pure product, but also significant economic benefits.     

Simultaneous optimal selection of design and manufacturing tolerances with alternative manufacturing process selection

Tolerance specification is an important part of mechanical design. Design tolerances strongly influence the functional performance and manufacturing cost of a mechanical product. Tighter tolerances normally produce superior components, better performing mechanical systems and good assemblability with assured exchangeability at the assembly line. However, unnecessarily tight tolerances lead to excessive manufacturing costs for a given application. The balancing of performance and manufacturing cost through identification of optimal design tolerances is a major concern in modern design. Traditionally, design tolerances are specified based on the designer’s experience. Computer-aided (or software-based) tolerance synthesis and alternative manufacturing process selection programs allow a designer to verify the relations between all design tolerances to produce a consistent and feasible design. In this paper, a general new methodology using intelligent algorithms viz., Elitist Non-dominated Sorting Genetic Algorithm (NSGA-II) and Multi Objective Particle Swarm Optimization (MOPSO) for simultaneous optimal selection of design and manufacturing tolerances with alternative manufacturing process selection is presented. The problem has a multi-criterion character in which 3 objective functions, 3 constraints and 5 variables are considered. The average fitness factor method and normalized weighted objective functions method are separately used to select the best optimal solution from Pareto optimal fronts. Two multi-objective performance measures namely solution spread measure and ratio of non-dominated individuals are used to evaluate the strength of Pareto optimal fronts. Two more multi-objective performance measures namely optimiser overhead and algorithm effort are used to find the computational effort of NSGA-II and MOPSO algorithms. The Pareto optimal fronts and results obtained from various techniques are compared and analysed.     

Developing control and integration software for flexible manufacturing systems

The slow growth of computer-integrated manufacturing is attributed to the complexity of designing and implementing their control and integration software. This article expands on a methodology for designing and implementing this software that was introduced in [16]. The goal of this methodology is to build flexible and resuable control and integration software for computer-integrated manufacturing systems. It hinges upon the concepts of software/hardware components, their assemblages, a distributed common language environment, formal models, and generic controllers. Major sources of flexibility are obtained by decoupling process plan models from the model of the factory floor and by using a generic controller. Reusability is achieved by building selfcontained software/hardware components with general, possibly parametrized, interfaces. The interplay between simulated and actual hardware internals of software/hardware components is used as the basis of a testing strategy that performs off-line simulation followed by on-line testing.The methodology has been applied in designing and implementing the control and integration software of an actual Prismatic Machining Cell. The article also reports on the details of this implementation.The names of the authors appear in alphabetical order.     

Database reverse engineering: From the relational to the binary relationship model

This paper describes an algorithmic method for transforming a relational database schema to a binary-relationship one. The source schema may consist of relations that are at any level of normalization, and the designer may add semantic information on the source schema, such as the definition of candidate keys, foreign keys, functional dependencies of various types, multi-valued dependencies, many-to-many constraints, inclusion dependencies, and others. Based on this information, the multi-stage transformation algorithm applies mapping rules to generate object-types, binary-relationships and constraints in the target conceptual schema. The method is implemented as a PC-based tool, utilizing Ingres, SQL and C, and is part of a comprehensive database design tool for both forward and reverse engineering.     

A non-dominated sorting genetic algorithm based approach for optimal machines selection in reconfigurable manufacturing environment

This paper deals with a problem of reconfigurable manufacturing systems (RMSs) design based on products specifications and reconfigurable machines capabilities. A reconfigurable manufacturing environment includes machines, tools, system layout, etc. Moreover, the machine can be reconfigured to meet the changing needs in terms of capacity and functionality, which means that the same machine can be modified in order to perform different tasks depending on the offered axes of motion in each configuration and the availability of tools. This problem is related to the selection of candidate reconfigurable machines among an available set, which will be then used to carry out a certain product based on the product characteristics. The selection of the machines considers two main objectives respectively the minimization of the total cost (production cost, reconfiguration cost, tool changing cost and tool using cost) and the total completion time. An adapted version of the non- dominated sorting genetic algorithm (NSGA-II) is proposed to solve the problem. To demonstrate the effectiveness of the proposed approach on RMS design problem, a numerical example is presented and the obtained results are discussed with suggested future research.     

Expert systems in manufacturing. Part 2: A management framework for expert-systems innovation and technology transfer

Current approaches to expert systems technology transfer have tended to focus upon the marketing and servicing of technology capabilities and potential whilst remaining uncertain about the process factors which determine how this technology may be applied and adopted effectively. Furthermore, much of current expert systems research work and literature addresses these issues from the viewpoint of the supplier or donor whilst overlooking the importance of human and organisational perspectives which shed light on the means of delivery and take-up within the recipient organisation. The paper, the second of two that look at expert systems innovation in manufacturing, argues for greater consideration of the characteristics, processes and mechanisms of technology transfer. It defines a new conceptual basis for technology transfer which stresses a ‘needs-driven’ process of change; this highlights the importance of context as well as content in expert systems transfer and implementation. From this, a management framework is outlined and is used to rationalise the transfer problems and needs described in the first paper following a survey of 145 manufacturing users. It is also shown how this framework may be used to understand more about the multi-level and multi-dimensional needs and effects of technology induced change and therefore how it may be used to help senior management strategically plan and co-ordinate expert systems programmes in their organisations.     

A decision support system for the selection of computer-integrated manufacturing technologies

The adoption of computer-integrated manufacturing (CIM) offers manufacturing organizations many tangible and intangible benefits which enable them to produce products of high quality at low costs. However, the selection and evaluation of CIM is a complex process as it involves the consideration of many parameters to ensure that the selected technology meets the requirements of individual companies. This paper describes the development of a quantitative/qualitative decision support system for the evaluation of CIM which takes into consideration the objectives and operating characteristics of a company, thus ensuring that the selected technology matches the individual needs of that company. The methodology used in the decision support system is based on a combination of the analytical hierarchy process (AHP) and database technology. The AHP provides a means to consider both the tangible and the intangible benefits of CIM while databases are used to store the knowledge about the various benefits that CIM may offer. The system has been implemented in EXCEL, which fully automates the evaluation process. A case study is also presented to illustrate the capability of the proposed decision support system.     

Learning process in a class of computer integrated manufacturing systems with parametric uncertainties

The paper is concerned with a class of manufacturing processes described by a relational knowledge representation containing unknown parameters. Two kinds of the manufacturing processes with different structures of material and task flow are considered. For these kinds the algorithms of learning and control for the central decision support computer system integrating the manufacturing process are presented. The learning process consists in using the results of step by step knowledge validation and updating to the determination of the current control decisions. The idea of learning described in the paper may be considered as a generalization of the known concept of the adaptive control using the results of current identification. Simple illustrative examples, results of simulations for a simple case and additional remarks concerning related problems are included.     

计算机辅助设计的技术应用探究

应用计算机辅助设计不仅可以提高产品的设计精度,还能缩短产品的开发周期,进而提高产品质量。计算机辅助设计技术在我国社会的各个领域都获得了较为广泛的应用。在该技术不断发展的过程中,计算机辅助设计技术具有了独特的发展特色。就计算机辅助设计的技术应用进行了探索,以期为更进一步优化计算机辅助设计的应用作出贡献。     

一种弹性的软件过程模型验证工具

过程模型验证是保证软件过程定义正确性的重要手段.针对目前过程模型验证中的一些问题,首先提出了一种以活动为中心的软件过程元模型,并以XML对其进行描述.在此基础上,从行为、资源、组织视图结合的角度,提出了保证软件过程模型正确性的语义约束规则.最后,提出了一种弹性的用于验证XML描述的过程模型的机制,并基于此实现了过程模型验证工具,来验证过程模型的正确性.     

Concurrent engineering utilities for controlling interactions in process planning

This paper presents two concurrent engineering tools for serving in process planning. The first one, as design for manufacturing utility, evaluates critical interactions between several types of machining features (i.e., holes, pockets, etc.) on prismatic parts, and modifies original design (if possible) and reflects the modifications to all down- and up-stream stations in CAD/CAM integration. The second one is for group technology and flexibility, by which products are designed according to the existing manufacturing system. Methodologies of the developed systems are illustrated with several examples throughout the paper.     

Clustering algorithm for solving group technology problem with multiple process routings

Cell formation is an important problem in the design of a cellular manufacturing system. Most of the cell formation methods in the literature assume that each part has a single process plan. However, there may be many alternative process plans for making a specific part, specially when the part is complex. Considering part multiple process routings in the formation of machine-part families in addition to other production data is more realistic and can produce more independent manufacturing cells with less intercellular moves between them. A new comprehensive similarity coefficient that incorporates multiple process routings in addition to operations sequence, production volumes, duplicate machines, and machines capacity is developed. Also, a clustering algorithm for machine cell formation is proposed. The algorithm uses the developed similarity coefficient to calculate the similarity between machine groups. The developed similarity coefficient showed more sensitivity to the intercellular moves and produced better machine grouping.