A comparative study of the performance of pure and hybrid group technology manufacturing systems using computer simulation techniques

Abstract

comparative study of the performance of pure and hybrid group technology manufacturing systems using computer simulation techniques C. L. ANG and P. C. T. WILLEytProblems of workload imbalance in Group Technology (OT) can be mitigated by transferring workloads from a congested machine centre in one cell to an alternative, less congested machine centre in another cell. Such inter-cell workload transfer results in a GT system which is a hybrid between pure GT (in which components are completely processed within a cell) and funotional layout (FL) (in which ('()lIlJHllwnts are router! from line depurt nu-nt of si III il<lI' mar-hines to .. mother until «nmpletely processed). Though inter-cell workload transfer' is oft.en used in practice, its effects on system performance in GT have nut heen evaluated. This paper describes a general purpose GT simulator which has been developed and the evaluation of workload transfer which has been carried out (Ang 1981). Various job and cell attributes are employed as criteria for initiating workload transfers and the results of such transfers are examined in terms of job satisfaction, scheduling effort and material handling as well as overall shop performance. The interacting effects of job allocation rules, priority dispatching rules and batch overlapping are investigated under varying degrees of deviation from 'pure' GT. The effects of changes in job mix and of increases in demand are also examined. So are the effects of unbalanced capacity and cell size. The implications of the results for the practical design and operation of GT systems are also discussed. IntroductionGroup technology overcomes many of the problems of conventional small-batch manufacture but it may lack the necessary flexibility to cope effectively with workload variations. Thus, problems under GT can be caused by changes in job mix and by increases in demand which lead to a workload imbalance both between cells and between machine centres within the same cell. One then has to decide how and when cell restructuring should be undertaken and, more practically, how loadbalancing problems can be eased and shop performance improved until the restructu ring can take place.Shop performance can of course be improved by the appropriate allocation of jobs to cells, by better scheduling and dispatching within the confines of the shop configuration, and by raising the transfer frequency between operations. However, the scope and possibilities for operating any production system to its best advantage

Next Generation Factory Layouts: Research Challenges and Recent Progress

“…While such organization may be adequate when part families are clearly identifiable and demand volumes stable, they become inefficient in the presence of significant fluctuations in the demand of existing products or with the frequent introduction of new ones. A more detailed discussion of the limitations of cellular manufacturing systems can be found in [1,4,11,40,59,70,77]. These limitations resulted in recent calls for alternative cellular structures, such as overlapping cells [1,39], cells with machine sharing [11,70], and fractal cells [4,59,77].…”

Design of flexible plant layouts

“…These limitations resulted in recent calls for alternative and more flexible cellular structures, such as overlapping cells [1], cells with machine sharing [2] [32], and virtual cellular manufacturing systems [8]. For highly volatile environments, certain authors have even suggested, as discussed earlier, a completely distributed layout, where copies of a given machine type are dispersed as much as possible throughout the shop floor [20] or the creation of multiple identical cells as in the fractal layout [21] [35].…”

“…While such organization may be adequate when part families are clearly identifiable and demand volumes are stable, they become inefficient in the presence of significant fluctuations in the demand of existing products or with the frequent introduction of new ones. A discussion of the limitations of cellular manufacturing systems can be found in [1], [2], [10], and [39].…”

Improving the performance of cellular manufacturing by a dynamic part assignment approach

“…In one study, the impact of sub-batch workload transfer on machine utilization in CM has been evaluated [15]. In another study, intercellular part transfer is proposed as an effective means of improving the efficiency of CM systems by directing the extra workloads from over-utilized machines to other cells [1]. Yet another approach to the problem of bottleneck machines is the development of alternative process plans and the rerouting of parts for increased scheduling flexibility [11].…”