A knowledge-based inspection process planning system for coordinate measuring machines

The coordinate measuring machine (CMM) is one of the most effective geometry inspection facilities used in manufacturing industry. To fully utilize its capabilities in a computer-integrated manufacturing (CIM) environment, we should integrate CMM with other systems and facilities. This paper presents the development of a knowledge-based inspection planner based on the fundamental principles of AI planning to integrate computer-aided design systems and CMMs. The issues involved in CAD-directed inspection process planning are examined; the task of inspection process planning is decomposed into a number of sub-tasks. According to the task decomposition, a knowledge-based planning system was designed with several modules. Each of these modules consists of a knowledge base, a control operator, a context and a communication interface. The knowledge base is the local knowledge source for problem solving; the control operator determines when and where the knowledge is applied; the context contains the initial planning state which is essential input part information, the intermediate planning states which result from the tentative decision made by the modules, and the goal state. The module interfacing was realized by directly calling procedures defined in other modules to pass the planning tasks and decisions. Examples are included to explain the planning knowledge and strategy.     

Automatic inspection planning within a feature-based CAD system

This paper describe a CIM system which incorporates automatic generation of inspection on plans for coordinate measuring machines (CMMs). Design is done in terms of form features. Associated with each feature are inspection plan fragments (IPFs) which are instances of inspection procedures. There are three basic types of plan fragments for CMMs: (1) fragments for checking the internal dimensions of a feature, (2) fragments for checking the relationships between features, and (3) modified fragments for use when the feature to be inspected intersects another feature. Using this approach, a list of suitable inspection points and approach vectors is generated. A path planner then combines the elements of the list to produce a valid inspection path for the CMM. The system is consistent with the accepted ANSI Y14.5M standard for dimensioning and tolerancing as well as with observed industrial practice.     

Probe orientation for coordinate measuring machine systems using design models

The rapidly increasing usage of coordinate measuring machines in computer-integrated manufacturing environments underscores the need for a more science-based approach to inspection than the current ad hoc approach now in place. In this context we address one element of the inspection process, namely, the location of sample points. We present a method for evaluating the location of sample points using the workpiece model from the design. Accessibility analysis is used to determine possible interference between the workpiece model and probe model.     

Decision support in computer-integrated manufacturing

This is a survey paper that addresses the issue of decision support in computer-integrated manufacturing (CIM). Since the complexity of the decision making process in manufacturing stems from the multilevel nature of the planning hierarchy, we emphasize the importance of adopting an integrated view of the planning hierarchy. We provide a framework for the development of a DSS for integrated manufacturing control that emphasizes a systems approach. Besides we consider some of the architectural aspects of a DSS in CIM. In particular, the specific architectural aspects of the management of data in CIM have been discussed at length.     

Building a CIM system for compound plant: Utilization of distributed processing system

The position of a production management system in a computer-integrated manufacturing (CIM) system is to serve as the nucleus of the plant CIM system that connects the plant production to other departments such as marketing, research and development, and distribution departments. A production management system that integrates the flow of goods with information in a plant, and thus manages production in it, was developed as the first step toward application of CIM to a powder plant. The method of building a distributed system is one way to build a CIM system. This method creates a system in the required function units, which are connected by a network to expand the system function. It offers advantages in extensibility, flexibility, and rapid implementation.     

Models for fault tolerance in manufacturing systems

The field of fault tolerance in computer science and engineering has been thoroughly investigated over a long period of time. A great number of different approaches have been presented on means for improving fault tolerance under certain error conditions in computerized systems. One important area that has introduced computers in order to enhance productivity, flexibility and economy, is manufacturing systems in order to acquire computer-integrated manufacturing (CIM). Using computers in a manufacturing system introduces new sources of difficulties, as well as providing new possibilities for overcoming erroneous situations that might disturb production. The aim of this paper, is to describe how the use of different configurations for a manufacturing system can improve fault tolerance. One specific erroneous situation which may occur in CIM is the partitioning of a network. This situation can be handled satisfactorily by using the suggested manufacturing system configurations. Additional improvements to fault tolerance can be achieved through the introduction of data buffers and material buffers, This approach is described in this paper.     

Strategies for planning and implementation of flexible fixturing systems in a computer integrated manufacturing environment

In general, for any manufacturing operation to be successful, parts must be located and held to remain in position and orientation when subjected to external forces during the manufacturing operations. The traditional approach to fixturing involves designing and manufacturing special-purpose fixtures. These fixtures are generally dedicated devices designed and manufactured for specific parts and manufacturing operations. Flexible fixturing technology involves employing a single fixturing system to hold workpieces of various shapes and sizes. Such systems have reached the embryonic stage of implementation into manufacturing environment. Therefore the integration of current and future flexible fixturing systems into the manufacturing processes becomes an important issue for future work in computer-integrated manufacturing (CIM) environment.

The approach to CIM is dependent on the functional model of the company. Therefore, the implementation of any sub-systems within it must be studied on an individual basis. However, in order to plan and implement new technologies, such as flexible fixturing systems, within CIM environment, certain requirements must be met and guidelines must be followed. The strategies for planning and implementation of flexible fixturing systems within the larger frame work of CIM environment are presented. Some guidelines for designing and developing the interconnection of the data bases are also discussed.     

Controller area network (CAN) for computer integrated manufacturing systems

Communication acts a central role in computer-integrated manufacturing (CIM). The choice of communication system widely determines the capability and productivity of a factory as a whole. Moreover, in the implementation of CIM systems, the costs associated with the interconnection of the individual CIM components are very important. In CIM, communication is largely used to control programmable manufacturing equipment. Here, the time requirements are high, and error-free data transmission is a necessity. Fieldbuses are special form of local area network dedicated to applications in the field of data acquisition and the control of sensors and actuators in machines or on the factory floor. Many fieldbus standards exist in the market today. Each of them has been invented at different periods by different companies and for different purposes. Controller area network (CAN) is one of the most popular fieldbuses. The highest advantages of CAN are its low cost, abundance of silicon technology, and reliability in networking multiple real-time systems. CAN is a multimaster bus topology and has shown to be very efficient medium for error detection and fault tolerance. CAN's technical specifications are defined in the ISO/OSI network layer spans just two layer of the model. CAN specifies, in many innovative ways, the physical signaling over the media, data formats, timing, error recovery, protocols and arbitration. It does not define the media itself and its connectors, and also the upper layers (usually software) of the model.     

Intelligent knowledge based expert inventory control system for computer integrated manufacturing

The paper discusses the framework and development of an expert inventory management system for integrative manufacturing planning. The system developed with an artificial intelligent language provides a linkage between management and computer-integrated manufacturing(CIM), has the following major elements: data base to represent a hierarchical tree using recursive objects on different levels; knowledge base containing heuristic rules; goal oriented interaction; and backtracking interface procedures. Potential benefits of the system includes: better manufacturing planning, reduced inventory levels and production lead times, and consistent inventory control records.     

A modeling technique for loading and scheduling problems in FMS

In recent years, due to highly competitive market conditions, it has become necessary for manufacturing systems to have quick response times and high flexibility. Flexible manufacturing systems (FMS's) have gained attention in response to this challenge. FMS has the ability to produce a variety of parts using the same system. However this flexibility comes at the price, which is the development of efficient and effective methods for integrated production planning, and control.In this paper, we analyze the production planning problem in flexible manufacturing systems. We address the problems of part loading, tool loading, and part scheduling. We assume that there is a set of tools with known life and a set of machines that can produce a variety of parts. A batch of various part types is routed through this system with the assumption that the processing time and cost vary with the assignment of parts to different machines and assignment of various tool sets to machines. We developed a mathematical model to select machines and assign operations and the required tools to machines in order to minimize the summation of maximum completion time, material handling time, and total processing time.We first integrate and formulate loading, and routing, two of the most important FMS planning problems, as a 0–1 mixed integer programming problem. We then take the output from the integrated planning model and generate a detailed operations schedule. The results reported in this paper demonstrate the model efficiency and examine the performance of the system with respect to measures such as production rate and utilization.     

Quality control for deep x-ray lithography (LIGA): a preliminary metrology study

The x-ray lithography process is time-consuming and costly. The use of process design rules is essential along with CAD designs that should fulfil the specifications of dimension and roughness. Parameters such as the material of mask membrane, the technique to produce the mask, the resist used (poly (methyl-methacrylate) [PMMA], epoxy based photoresist SU-8), the synchrotron power and synchrotron spectrum do have an effect on the final geometry of the fabricated parts. To evaluate these parts, high accuracy metrology is essential. KIT/IMT and NPL have two different co-ordinate measuring machines (CMMs) designed for millimetre scale geometry measurements to micrometer accuracy. Test structures of various sized holes and columns, made by deep x-ray lithography in PMMA and electroformed in metal, have been measured by these two different CMMs. A comparison of the measurements taken from these two micro-CMMs will be presented and discussed. The outcome of these preliminary results on the x-ray lithography process will be shortly described.     

基于自定义特征的飞机结构件智能检测规划技术

飞机结构件常用坐标测量机检测形状特征的加工质量。为了满足飞机结构件需要检测复杂形状特征以及便于拓展形状特征检测范围的迫切需求,研究了独立于形状特征类型的特征定义框架及统一的特征识别算法;提出了检测知识驱动的测量点智能分布方法;设计了结合聚类和改进模拟退火算法的测量方向优化算法;实现了基于自定义特征及检测知识的智能检测规划。该技术已在多个重大航空产品的研制中得到应用,显著提升了飞机结构件检测规划的效率和智能化水平。     

Implementing a Manufacturing Information System

The adoption of a computer-driven technology should lead to cost reduction, improved control, and increased profitability. However, it should not be adopted just because it has worked well in other organizations. The corporate staff groups, in their zeal to please management, often lose objectivity and plunge into the new system adoption process to the detriment of the organizational welt-being. This article discusses the advantages of implementing a manufacturing information system to help MIS managers coordinate a strategy for CIM - computer-integrated manufacturing.     

Selection of computer-integrated manufacturing technologies using a combined analytic hierarchy process and goal programming model

Investment in computer-integrated manufacturing (CIM) is a multi-attribute problem, which includes both qualitative and quantitative factors. In order to select the best set of CIM alternatives among the competing ones it is necessary to make a trade off between the quantative and qualitative factors some of which may conflict. Selection of appropriate CIM alternatives is vital in manufacturing companies’ long-term competitiveness, and it requires development of selection models. The selection model must consider various quantative and qualitative objectives and constraints simultaneously. For example, companies have generally limited funds to invest in new advanced technology. The size of the allocated fund limits the types and number of CIM alternatives a company can select in a given time period. In this article, a combined model of the analytical hierarchy process and goal programming is proposed to consider multiple objectives and constraints simultaneously. A real-world example is provided to illustrate the application of the combined approach.     

An information system for computer-integrated manufacturing systems

One of the main problems when implementing the computer-integrated manufacturing (CIM) concept concerns information integration. In order to support information integration, an information system provided with suitable data models is required. In this paper an information system is presented, which fulfils the requirements for an appropriate information management in CIM. For this purpose, an EXPRESS-oriented information system has been built on top of a commercial relational DBMS. The conceptual model of the information is built in EXPRESS and then parsed and translated to the corresponding relational constructs. A data access interface has been implemented which allows EXPRESS-oriented data manipulation. The information system was developed inside ESPRIT project No. 2202 CIM-PLATO “CIM System Planning Toolbox” to integrate the information used by the tools developed for flexible manufacturing system planning.     

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.     

An expanded SEMATECH CIM framework for heterogeneous applications integration

A significant effort in recent computer-integrated manufacturing (CIM) development was carried out by SEMATECH who had laid out and created an open framework for the integration of manufacturing execution system applications running in semiconductor industries at the factory operation level. This paper presents the feasibility to incorporate basic manufacturing applications at the factory engineering level, which include product design, process planning, and material requirement planning, into the SEMATECH CIM framework to form a generic framework across both factory operation level and factory engineering level. The CIM framework established in this paper was aimed to provide a reusable integrated system framework that clearly specifies the functional interface boundaries and standard information model of the required components, in general, manufacturing systems at both factory operation and factory engineering levels. Standard unified modeling language (UML) diagrams and Petri nets have been utilized to model and analyze the specifications and dynamic behaviors of this generic CIM framework. The goal is to build a framework by creating a common, modular, flexible, and integrated object model that unifies an advanced object-oriented architecture concept and heterogeneous manufacturing application development in an open and multisupplier CIM system environment.     

Flexibility in component manufacturing systems: evaluation framework and case study

Traditional component manufacturing systems have been optimized for either small scale craft production or for mass production of a small variety of high volume parts. Trends towards intermediate volumes and larger variety of parts have exposed the need for intelligently embedding flexibility in manufacturing systems and processes. The literature offers only few attempts to value component fabrication flexibility in a systematic way. In this article a 5-step framework for valuing flexibility and ranking of manufacturing processes under uncertainty is developed. A discrete time simulation is used to predict profit, remaining tool value and machine utilization as a function of three probabilistic demand and specification scenarios. A case study demonstrates the simulation and contrasts both a high volume (automotive) and a low volume (aerospace) market situation across six different processes ranging from punching to laser cutting. It is found that for intermediate, uncertain production volumes alternative manufacturing processes that embed flexibility carefully in one or more dimensions can outperform traditional processes that are either completely non-flexible (e.g., stamping) or completely flexible (e.g., laser cutting). It is also shown that flexibility in parts manufacturing is a complex topic because flexibility can be embedded in the parts themselves, in tooling or in the process parameters.     

Analysis of dynamic due-date assignment models in a flexible manufacturing system

This paper investigates the effects of dynamic due-date assignment models (DDDAMs), routing flexibility levels (RFLs), sequencing flexibility levels (SFLs) and part sequencing rules (PSRs) on the performance of a flexible manufacturing system (FMS) for the situation wherein part types to be produced in the system arrive continuously in a random manner. The existing DDDAMs considered are dynamic processing plus waiting time and dynamic total work content. A new model known as dynamically estimated flow allowance (DEFA) has also been developed and investigated. The routing flexibility of the system and the sequencing flexibility of parts are both set at three levels. A discrete-event simulation model of the FMS is used as a test-bed for experimentation. The performance measures evaluated are mean flow time, mean tardiness, percentage of tardy parts and mean flow allowance. The statistical analysis of the simulation results reveals that there are significant interactions among DDDAMs, RFLs, SFLs and PSRs for all the performance measures. The proposed DEFA model provides the minimum percentage of tardy parts in all the experiments. Regression-based metamodels have been developed using the simulation results. The metamodels are found to provide a good prediction of the performance of the FMS within the domain of their definition.     

Automated inspection planning of free-form shape parts by laser scanning

The inspection operation accounts for a large portion of manufacturing lead time, and its importance in quality control cannot be overemphasized. In recent years, due to the development of laser technology, the accuracy of laser scanners has been improved significantly so that they can be used in a production environment. They are noncontact-type-measuring devices and usually have the scanning speed that is 50–100 times faster than that of coordinate measuring machines. This laser-scanning technology provides us a platform that enables us to perform a 100% inspection of complicated shape parts. This research proposes algorithms that lead to the automation of laser scanner-based inspection operations. The proposed algorithms consist of three steps: firstly, all possible accessible directions at each sampled point on a part surface are generated considering constraints existing in a laser scanning operation. The constraints include satisfying the view angle, the depth of view, checking interference with a part, and avoiding collision with the probe. Secondly, the number of scans and the most desired direction for each scan are calculated. Finally, the scan path that gives the minimum scan time is generated. The proposed algorithms are applied to sample parts and the results are discussed.