Colin L. Moodie

Definition and classification of manufacturing flexibility types and measures

Flexibility is one of the most sought-after properties in modern manufacturing systems. Despite this interest, flexibility remains poorly understood in theory and poorly utilized in practice. One reason for this is the lack of general agreement on how to define flexibility: over 70 terms (types and measures) can be found in the literature. This paper concerns developing a framework and classification scheme for use in defining and classifying the various terms regarding flexibility found in manufacturing. The framework consists of six attributes: level of manufacturing requirements specification, manufacturing system specification, manufacturing environment specification, flexibility dimension, flexibility measurement approach, and time frame. A six-field hybrid classification scheme is developed based on this framework. The framework serves as a guide for developing new flexibility terms, whereas the classification scheme provides a mechanism for summarizing the important aspects of and assumptions behind a given term. The approach is demonstrated by using the classification scheme to classify over 50 existing flexibility terms. The results indicate that the classification scheme is an effective tool to aid in understanding different flexibility terms and how they compare to one another. At the same time, the difficulty of the classification exercise indicates the need for a suitable framework when defining such terms.

OPTIMAL BUFFER STORAGE CAPACITY IN PRODUCTION

SUMMARY Two models of steady-state production line systems are analysed using simulations to estimate the coefficients for an optimal solution to the problem of determining the buffer storage capacity for lines of varying length. The non-steady-stale case is then considered and the possibility of using a time-dependent control on buffer capacity during the transient period is investigated.

Solving cell formation problems in a manufacturing environment with flexible processing and routeing capabilities

In this paper, we investigate cell formation problems in a manufacturing system with flexible processing and routeing capabilities. Flexible processing means that a part can be manufactured by any one of several process combinations. Flexible routeing means that even when the processes are fixed, the part can traverse any one of several routes—each offering the same processes. The cell formation problems for these types of manufacturing systems are different from traditional problems. Traditional cell formation problems are for manufacturing systems with fixed processes and routes where one knows what machines will be used for manufacturing the parts. However, this information will not be available in the flexible systems discussed here, since a part can be completed by any one of the many different combinations of machines. In other words, it is possible to manufacture two identical parts using different sets of machines. Traditional cell formation techniques rely on knowing the specific machine usage in...

Machine layout with a linear single-row flow path in an automated manufacturing system

This paper investigates the machine layout problem with a linear single-row flow path within an automated manufacturing system. Traditional machine layout approaches can produce inappropriate layout designs because they often do not consider flow path characteristics, such as flow path configuration and feasible flow path direction. This paper investigates the effects of such flow path characteristics on machine layouts. A two-phase layout procedure that combines flow line analysis with simulated annealing is proposed. The procedure can be employed using a variety of evaluation criteria (minimize total flow distance, maximize number of in-sequence movements, and so on). Different layout procedures can be obtained by varying the flow line analysis method and temperature reduction strategy employed for simulated annealing. Experiments are performed to test the performance of different layout procedures for different combinations of flow path characteristics and quantities of machines. The experimental results provide vital information on selecting appropriate flow line analysis methods and temperature reduction strategies for different layout problems. Furthermore, the results will help designers determine appropriate evaluation criteria for different layout problems.

Application of expert systems and pattern recognition methodologies to facilities layout planning

Abstract This paper deals with two basic concepts of artificial intelligence (AI), from a facilities layout problem domain perspective. In this work, the facilities layout problem is treated as a multi-objective situation. From conventional multi-objective perspective, the philosophy underlying this work is not a different one. However, the qualitative constraints are handled via a symbolic manipulation structure. The two conceptualizations are: (a) an expert system and (b) a pattern recognition system. In the expert system, the heuristics used are based on the augmented transition networks of natural language processing. In the pattern recognition system, the use of productions rules to capture the expert knowledge is illustrated. For both the systems example problems are given.

Two sequence-pattern, matching-based, flow analysis methods for multi-flowlines layout design

Abstract In optimizing the layout design of a multi-product assembly environment, the analysis of the material flow is a vital ingredient. In a multi-product production environment, products are usually grouped together into families. Products of the same family group usually involve similar operations; however, it is common to see some difference in the operations and the operational sequences among these products. The design technique for the layout of multi-product flowlines should be able to resolve the difference among the operation sequence of these products. The ideal material flow in a good layout design should be mostly in-sequence flow. In-sequence flow usually has the benefits of smaller flow distance, easier control of the production process and easier material handling. This paper proposes two flow analysis methods that are designed to provide a better flow analysis for the design of multi-products flowline. The first method adopts the traditional line structure for analysis. The second metho...

A hybrid approach for concurrent layout design of cells and their flow paths in a tree configuration

The layout design of multiple-cell automated manufacturing systems includes cell layout design and flow path layout design. Traditional layout methods often treat these two as separate problems and the sequence for solving them is usually cell layout first and flow path layout later. However, approaches of these kinds have one major drawback, that is, they may produce cell layouts that are awkward or difficult for designers to conduct flow path layouts, or cell layouts that do not turn out to be as good as expected after flow path layouts have been performed. Other drawbacks of traditional layout methods include irregular shapes of cells, inaccurate calculations of flow distances, etc. This paper addresses the layout problem of cells and their connecting flow paths in a tree configuration. The proposed layout procedure is designed to avoid the aforementioned drawbacks of traditional layout methods by emphasizing concurrent layout design of cells and flow paths. It combines a search algorithm and mathematical programming models. The search algorithm has a backtracking procedure that allows one to explore alternative layouts, while the mathematical programming models help one obtain accurate layouts of cells and flow paths. The proposed layout procedure also interacts with designers and allows designers to include their qualitative consideration into the layout design. As a result, one can obtain more accurate and good-quality layouts with the proposed layout procedure.

A modelling of interactive facilities layout designer reasoning using qualitative patterns

SUMMARY A modelling of interactive facilities layout designer reasoning for the purpose of improving the quality of solution currently available in the layout literature. Some of the constraints which are laborious to explore interactively, are enumerated by automated reasoning. The facilities layout design task is conceived as a multi-agent collaborative reasoning problem. The described approach is fundamentally different from previous approaches in three ways: (i) The reasoning is focused on the automated identification and rectification attempts on a set of qualitative patterns (termed qualitative layout anomalies or QLAs). (ii) The problem is solved by context-based reasoning, with each context originating from a different starting solution. The contexts allow one to jump into interesting regions of the solution space, (iii) An automated interface of the reasoning process and linear optimization is developed to solve the layout problem. This makes it more convenient to enumerate the solution space mor...

Knowledge Based Control System for Automated Production and Assembly

This paper describes an experimental investigation into the routing of jobs in an automated production and assembly facility using a knowledge based system.

A framework for integrated assembly systems: humans, automation and robots

Abstract Seeking to improve work design, this study examines the abilities and limitations of combined utilization of humans, automation, conveyors and robots. The comparison leads to the objective of this analysis, of enhancing the productivity of robots and automation while increasing work satisfaction and productivity for the humans. Towards the goal of achieving this objective, consideration is given to the development of a framework for the selection of the appropriate robot, machine and conveyor to complement the human in a work environment. A case study is used to illustrate the usefulness and efficiency of the proposed approach to systems optimization.