Peter O'Grady

INTEGRATING KANBAN TYPE PULL SYSTEMS AND MRP TYPE PUSH SYSTEMS: INSIGHTS FROM A MARKOVIAN MODEL

Approaches to multistage production scheduling can be conveniently classified into push type (i.e., Materials Requirements Planning (MRP) systems) or pull type (i.e., kanban systems). Each is generally thought to have both advantages and disadvantages. In this paper, a hybrid push/pull strategy is developed with the aim of gaining the advantages of both approaches. Material flow between work centers is regulated using the standard single card kanban/pull arrangement. Superimposed on this is the MRP-type information flow which feeds forward demand information directly to one or more (but not necessarily all) work centers. A general N-stage hybrid push/pull model is developed. The use of the approach is illustrated using 3-stage and 4-stage serial flowlines. The results indicate that the push/pull approach has lower inventory levels and a better response to demand changes than the pure pull system. The hybrid approach seems to combine many of die advantages of MRP approaches while retaining much of the simp...

An intelligent cell control system for automated manufacturing

Cell control forms one level of a hierarchical approach to the control of automated manufacturing systems. This paper describes the application of the artificial intelligence techniques of blackboard and actor based systems for intelligent cell control in a framework termed Production Logistics and Timings Organizer (PLATO-Z). The blackboards required are described and the implementation is detailed. The implications of some practical considerations are also described.

An artificial intelligence-based constraint network system for concurrent engineering

This paper presents a new approach to concurrent engineering, namely the use of artificial intelligence constraint networks to advise the designer on improvements that can be made to the design from the perspective of the products life-cycle. The difficulties associated with performing concurrent engineering are reviewed, and the various approaches to concurrent engineering are discussed. The requirements for a system to support concurrent engineering are indicated. An overview of constraint networks is given and this leads into a description of SPARK, an artificial intelligence constraint network systems for concurrent engineering. The operation of SPARK is illustrated by considering an example application of printed wiring board manufacture. The advantages of SPARK include being flexible enough to allow the designer to approach a problem from a variety of viewpoints, allowing the designer to design despite having incomplete information, and being able to handle the wide variety of life-cycle informatio...

Loading a flexible manufacturing system

Abstract This paper examines the problem of master scheduling for an FMS in Scotland containing six CNC horizontal boring machines. A multiple criteria approach is used to choose the compatible subset of candidate orders for processing by this FMS, subject to resource constraints and potentially conflicting performance objectives. A structured framework for conflict resolution is described and compromise solutions are obtained using standard mathematical programming software.

Configuring computer systems through constraint-based modeling and interactive constraint satisfaction

Abstract A major problem in the computer industry, as with many other industries, is ensuring that the products ordered by a customer are viable products and that they can be delivered at the quoted price. The inability of companies to solve this problem results in an enormous expense for a company. In this paper we present an approach to solving this problem in the computer industry through constraint-based modeling and interactive constraint satisfaction. pc/con , a Personal Computer Configuration System, has been built within a computer-based environment called Saturn. The development of pc/con and related work is discussed. Saturns architecture is presented and an example session with pc/con is demonstrated. We show how Saturn and pc/con have the features and capabilities necessary to support the extremely large variety of products and to support the maintenance of a configuration system for a rapidly and continuously changing product line. This approach would also appear to be applicable to other industries where there is a wide product variety.

A concise review of flexible manufacturing systems and FMS literature

Abstract The widespread popularity of Flexible Manufacturing Systems (FMS) has resulted in a prolific bibliography of literature describing several frameworks for analysis, planning and control of this automated mode of production. In this paper we review literature and discuss both the major characteristics of FMS and the contemporary decision support systems that have emerged to address the planning and control problems inherent in FMS.

A constraint programming language for Life-Cycle Engineering

Abstract Life-Cycle Engineering is a design methodology that takes into account the mutually constraining influences of product manufacturability, testability and maintainability as well as functionality. We are using non-directional constraint networks to model these mutually constraining influences in order to enable product designers to design more successful products without sacrificing functionality. To do this, we have developed Leo, a constraint programming language whose features have been specifically chosen to support Life-Cycle Engineering. In this paper, we introduce Leo and show its operation in the domain of printed wiring board design.

The design of flexible manufacturing systems

Abstract Flexible manufacturing systems (FMS) have promised many benefits but there is evidence that the implementation of FMS is often fraught with difficulty. One result is that the implementation rate of FMS is much lower than has been expected. The aim of this paper is to review the approaches that can be used to design an FMS. A review is given of the work done to date on the design an FMS in the areas of facilities design, material handling system design, control system design, and scheduling. In each instance, the major research and development issues are given. Through examining the tools and approaches that are used to design these four phases it is apparent that no integrated design methodology exists for FMS. The tools available are not specifically tailored for FMS and their unique integrated form. Because of the lack of integration, an FMS must be designed by examining the four phases independently even though the design decisions from each area affect the efficiency of the other areas.

A constraint-system shell to support concurrent engineering approaches to design☆

Abstract This paper describes SATURN, a powerful constraint-system shell that provides knowledge integration and reasoning features ideally suited to supporting concurrent engineering approaches to design. SATURN is a logic-based constraint modeling system, tightly coupled with a relational database, and supported by a truth maintenance system. This paper presents SATURNs architecture and its modeling and manipulation techniques. An example application in automated-storage-and-retrieval-system design is provided to illustrate how a SATURN constraint-based model is constructed by a concurrent engineering design team, which then can be used by a product designer to create a feasible design. Unique features of this constraint-system shell include its rich knowledge representation facilities, its seamless integration of forward, backward and relational database inferencing, and its engineer-oriented user interface.

A general search sequencing rule for job shop sequencing

This paper sets out, an approach to the job shop sequencing problem by determining the priority of a job from a linear combination of the basic quantities of operation times and due date. This achieves a simple yet unified format. Furthermore, since these basic quantities are used in fixed linear combinations in the majority of well-known simple heuristics, the rule outlined in the paper is capable of representing such heuristics as special cases within its framework. A performance function is used to assess the effectiveness of the rule and no limitations are imposed on its structure. The form of the variable priority rule is then determined by a computer search routine basing its decisions on the values of the performance function. This overall approach to job shop sequencing we term the search sequencing rule (SSR).