Jannes Slomp

Designing a new mathematical model for cellular manufacturing system based on cell utilization

Abstract In this paper, we propose a new mathematical model for cell formation in cellular manufacturing system (CMS) based on cell utilization concept. The objective of the model is to minimize the exceptional elements (EE) and number of voids in cells to achieve the higher performance of cell utilization. A number of test problems from the literature are carried out to verify the good ability of the proposed model to form part–machine grouping in comparison of the previous models ([S.J. Chen, C.S. Cheng, A neural network-based cell formation algorithm in cellular manufacturing, International Journal of Production Research 33 (2) (1995) 293–318], [I. Mahdavi, O.P. Kaushal, M. Chandra, Graph-neural network approach in cellular manufacturing on the basis of a binary system, International Journal of Production Research 39 (13) (2001) 2913–2922]).

A lean production control system for high-variety/low-volume environments: a case study implementation

Due to the success of lean manufacturing, many companies are interested in implementing a lean production control system. Lean production control principles include the levelling of production, the use of pull mechanisms and takt time control. These principles have mainly been applied in high volume flow shop environments where orders move through the production system in one direction in a limited number of identifiable routing sequences. This article investigates how lean production control principles can be used in a make-to-order job shop, where volume is typically low and there is high variety. We show how production levelling, constant work in process, first in first out and takt time can be integrated in a lean production control system. A case study is presented to illustrate the design and phased implementation of the system in a typical dual resource constrained production environment. The case study demonstrates that lean production control principles can be successfully implemented in a high-variety/low-volume context. Implementation led to a reduction in flow times and an increase in the service level achieved, with on-time delivery performance improving from 55 to 80%.

A multi-objective procedure for labour assignments and grouping in capacitated cell formation problems

A hierarchical methodology for the design of manufacturing cells is proposed, which includes labour-grouping considerations in addition to partmachine grouping. It is empirically driven and designed for an interactive decision environment, with an emphasis on fast execution times. The method synthesizes the capabilities of neural network methods for rapid clustering of large partmachine data sets, with multi-objective optimization capabilities of mathematical programming. The procedure includes three phases. In Phase I, part families and associated machine types are identified through neural network methods. Phase II involves a prioritization of part families identified, along with adjustments to certain load-related parameters. Phase III involves interactive goal programming for regrouping machines and labour into cells. In machine grouping, factors such as capacity constraints, cell size restrictions, minimization of load imbalances, minimization of intercell movements of parts, minimization of new machines to be purchased, provision of flexibility, etc. are considered. In labour grouping, the functionally specialized labour pools are partitioned and regrouped into cells. Factors such as minimization of hiring and cross-training costs, ensuring balanced loads for workers, minimization of intercell movements of workers, providing adequate levels of labour flexibility, etc. are considered in a pragmatic manner.

Sequence-dependent clustering of parts and machines : a Fuzzy ART neural network approach

This study addresses the problem of identifying families of parts having a similar sequence of operations. This is a prerequisite for the implementation of cellular manufacturing, group technology, just-in-time manufacturing systems, and for streamlining material flows in general. A pattern recognition approach based on artificial neural networks is proposed, and it is shown that the Fuzzy ART neural network can be effectively utilized for this application. First, a representation scheme for operation sequences is developed, followed by an illustrative example. A more comprehensive experimental verification, based on the mixture-model approach is then performed to evaluate its performance. The experimental factors include size of the part-machine matrix, proportion of voids, proportion of exceptional elements, and vigilance threshold. It is shown that this neural network is effective in identifying good clustering solutions, consistently and with relatively fast execution times.

On the who-rule in Dual Resource Constrained (DRC) manufacturing systems

The who-rule is a labour allocation rule used in labour and machine-limited dual resource constrained (DRC) systems. A who-rule selects one worker out of several workers to be transferred to a work centre. By means of a practical instance, the paper shows that the who-rule plays a role in the daily practice of worker assignment. Previous simulation studies, however, either have not mentioned the who-rule or have treated it as a fixed factor. The present study will explore the need of including the who-rule in simulation studies. It will describe in detail at what decision moments the who-rule needs to be applied in simulation. Further, it will explore the flow time effects of applying different who-rules in several DRC systems where labour flexibility is limited and workers differ with respect to task proficiencies, the number of skills they possess and the loads of work centres for which they are responsible. As with other labour allocation rules, the impact of the who-rule depends on the specific DRC shop modelled. The paper will show that the average labour utilization, and the types and extent of worker differences, determine the impact of the who-rule on shop performance.

The evolution of a cellular manufacturing system – a longitudinal case study

This paper describes the evolution of a cellular manufacturing system in a medium-sized company over a 13-year period. The objective of this paper is to analyze the arguments that gave rise to the nearly continuous readjustment of the design of the cellular manufacturing system of this company and the direction in which these adjustments took place. The study indicates that two interrelated factors played an important role in the decision to change the system: the market and manufacturing technology. Analysis of these factors offers important insights into the aspects that need to be taken into account in cell formation. It is argued that a cellular system should reflect market characteristics. New technology, furthermore, demands specialized cells, producing in a multi-shift situation. These two developments point in the direction of market-oriented, reasonably sized, functionally organized manufacturing units. It is argued that market developments, new manufacturing technology and modern production control systems will probably constrain the application area of cellular manufacturing

The capacitated cell formation problem: a new hierarchical methodology

In this paper, a hierarchical methodology for the design of manufacturing cells is proposed, synthesizing the capabilities of new pattern recognition methods for rapid clustering of large part-machine data sets, with multi-objective optimization capabilities of mathematical programming. The procedure includes three phases. In Phase I, part families and associated machine types are identified through neural network methods for pattern recognition. Phase II is a cell formation phase that involves the assignment of part families and individual machines to create independent cells. It takes into account several factors such as capacity constraints, cell size restrictions, minimization of load imbalances and provision of flexibility, Phase III attempts to minimize inter-cell traffic further for families that may still have to be processed in more than one cell. The methodology is illustrated using several examples.

An integrated model for part-operation allocation and investments in CNC technology

Abstract This study addresses the issue of investment appraisal of new technology, specifically computer numerical control (CNC) machine tools in conjunction with optimal allocation of parts and operations on CNC machines as the investments take place. Part-operation allocation is the allocation of parts and operations to either the conventional machines or to the new technology as they are acquired. It is shown that part allocation is an important consideration in the assessment of profitability from investments in CNC technology. A mixed integer programming model is presented to (1) determine the optimal allocation of parts and operations to conventional machines and to new CNC machine tools; and (2) determine the optimal investment sequence and timing of investments in CNC machine tools. The optimality criterion is based on a maximization of net present value (NPV) over a specified planning horizon. The application of the model is illustrated using a numerical example, and the implications for industrial practice are also indicated.

AN INTEGRATED APPROACH FOR THE CELL FORMATION AND LAYOUT DESIGN IN CELLULAR MANUFACTURING SYSTEMS

In this paper, a comprehensive model is presented for cell formation and layout design in cellular manufacturing systems (CMS). The proposed model incorporates an extensive coverage of important operational features and especially layout design aspects to determine optimal cell configuration and Intra and Inter-cell layout in CMS. Hence, proposed integrated approach attempts to design intra and inter-cell layout and material handling flow path structure simultaneously. We examine the great potential benefits of providing these features consist of routing flexibility, operation sequence, machine capacity, considering number of cells as a decision variable, un-equal dimension of machines, free machines and cells orientation, and considering pickup and drop off station for each cell. In order to show the effects and important of integrated design in the CMS, two approaches, sequentially and integrated, have been investigated and demonstrate the integrated approach improve the quality of obtained solution. The proposed model is a mixed integer non-linear programme. Linearisation procedures are proposed to transfer it into a linearised mixed integer programming formulation. Computational results are presented with the linearised formulation. We presented several enhancements in terms of valid inequalities and extensions to the proposed model in order to improve its computational performance. Finally, concluding remarks are provided.

Struggling with solutions: a case study of using organisation concepts

Engineers contribute to the constant flow of new tools and organisation concepts. These tend to be presented as solutions to existing organisational problems. These solutions may become problems themselves, however. We present a longitudinal case of how a truck manufacturer struggled with various similar and dissimilar concepts in realising organisational changes. Whilst it may seem idiosyncratic, the companys struggles are probably typical for organisational change praxis. Reflecting on the case, we present a model to help practitioners reflect on their use of concepts and tools (thereby arguably contributing to the issue we signal).