Experiments were conducted with a simulation model of a flow shop with prohibited early shipments under a wide variety of conditions including congestion, which was modeled separately as "blocking" and as "material handling cost (MHC)." Congestion was found to significantly degrade most standard measures of shop performance, with stronger effects at high utilization and with blocking. Contrary to intuition, controlled release was found to be of little benefit under blocking. Further, controlled release under both blocking and MHC would appear to have a negative effect on flow time, percent of jobs tardy, work in process (WIP) cost, and late cost. Early cost and MHC were shown to benefit from controlled release under some circumstances, so total cost can benefit from controlled release depending on system configuration and cost parameters. With one such combination, a moderate level of release control was found to perform better on total cost than either immediate release or a stronger level of control.
[...] Since the interactions between release rule and the other factors including congestion and congestion effect were mostly not significant, the experiments fail to show that controlled release is advantageous, even in the presence of congestion. Table 3 ANOVA (Probability Results are Random) Percent Factor(s) Flow Tardy MHC WIP Early Late-M Rel [...]
[...] While the indicated parameter values are certainly not claimed to be optimal, it is believed that they represent good performance Main Experiments The main experiments were designed to obtain a more complete picture of the degree to which shop performance with and without congestion is affected by controlled release under various experimental conditions. To do so, a full factorial analysis of six factors was conducted as follows (parameter settings for the various options are provided above): --three release rules: IMM, MIL, and MXJC1. [...]
[...] The priority jobs are checked in ascending order of Ri and are released if the release action does not exceed maximum allowable jobs or work in the shop as limited by one of rules MXWS, MXWS1, MXJS, MXJS1, or MXJC1. The following priority rules are available for sequencing decisions at the three work centers. Although the model is capable of using different rules in different centers, all centers used the same rule for this research. These rules are also available for use in the release process in that each can be selected for use as the sequence in which jobs in the pre-shop queue are checked for release: First-come-first-served (FCFS): select jobs for processing (or release) in their order of arrival to the work station (or shop). [...]
[...] IMM Release Rule Performance at MHC=$ 1.00 Release* Flow % Tardy MHC WIP Early Late-Med Tot-Med MIL/ MIL/ MIL/ MIL/ MIL/ IMM *MIL parameter is K1; all K2= 3.5 Note: lower values of K1 and K2 cause longer release delays, all other things equal Conclusions Experiments were conducted with a simulation model of a flow shop with prohibited early shipments under a wide variety of conditions including various congestion levels and two congestion effects (MHC and blocking). Results indicate that increased congestion degrades most measures of system performance, with stronger effects at high utilization and with blocking. [...]
[...] J., “Load-limited Order Release in Job Shop Scheduling Systems,” Journal of Operations Management, Vol No pp 44- Kanet, J. J. and D. P. Christy, “Manufacturing Systems with Forbidden Early Shipment: Implications for Setting Manufacturing Lead Times,” International Journal of Production Research, Vol No pp 783 13 - Karabati, S. and P. Kouvelis, Interface of Buffer Design and Cycle Scheduling Decisions in Deterministic Flow Lines,” Annals of Operations Research, Vol pp 295- Kim, S., K. R. Davis and J. F. Cox, Investigation of Output Flow Control, Bottleneck Flow Control and Dynamic Flow Control Mechanisms in Various Simple Line Scenarios,” Production Planning and Control, Vol No pp 15- Land, M. [...]
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