Rules In Job Shop Research Articles

Flow Time and Tardiness Based on New Scheduling Rules for Dynamic Shop Scheduling with Machine Breakdown

In this paper, a comparative study on the performance of scheduling rules in job shop. Four new dispatching rules are proposed. mean, maximum ,variance of tardiness and proportion of tardy jobs have been used to evaluate the performance of various scheduling rules. Breakdown level, shop load level was considered in the comparative study. The simulation result indicate the performance of dispatching rules is being influenced by Breakdown level, shop load level.

Towards an Integrated Workload Control (WLC) Concept: The Performance of Due Date Setting Rules in Job Shops with Contingent Orders

Workload control (WLC) is a production planning and control concept developed for make-to-order companies. Its customer enquiry management methodology supports due date setting, while its order release mechanism determines when to start production. For make-to-order companies, due date setting is a strategically important, complex task where unconfirmed jobs place demands on capacity which are contingent on a quotation being accepted by the customer. Yet most prior WLC research has begun at the order release stage with a set of confirmed orders with predetermined due dates. In contrast, this paper focuses specifically on customer enquiry management and uses simulation to compare and contrast the performance of 11 due date setting rules in a job shop where part of the workload consists of unconfirmed or contingent orders. The best results are achieved by a finite loading rule which explicitly considers the workload of contingent orders when estimating lead times. This enables demand to be levelled over time, allowing due dates to be short and reliable – thereby improving both the competitiveness of a make-to-order company and the customer service level it is able to offer. Future research should focus on integrating customer enquiry management, and its due date setting rule, with order release control.

Minimum tardiness scheduling in flow shops: Construction and evaluation of alternative solution approaches

Abstract Surveys of industrial scheduling practice show that meeting customer due dates is a critical concern for many manufacturing systems. While there is considerable research on the effectiveness of scheduling rules in job shops, very little work is reported on flow shops. Although scheduling rules developed for job shops can be applied in other systems as well, we show that the inherent structure of a flow shop can be utilized to construct effective solution procedures. In particular, for the total tardiness problem, we develop conditions for local optimality in a 2-machine flow shop, and use these results to generate an efficient improvement heuristic procedure. We also construct solution methods that utilize the notion of shifting bottlenecks. Our computational experience reveals the superiority and robustness of the proposed approaches under a variety of problem scenarios. The results of this study also indicate the need to look beyond permutation schedules for solving the flow shop tardiness problem. Furthermore, they suggest that the criterion for determining machine criticality needs to take the scheduling objective into consideration. While it appears intuitive to impute criticality on the basis of machine workloads and, therefore, emphasize the bottleneck machine for generating the shop schedule, this approach may frequently result in inferior system performance.

Due date based scheduling in a general flexible manufacturing system

AbstractDynamic scheduling of manufacturing systems for due date based objectives has received considerable attention from practitioners and researchers due to the importance of meeting due dates in most industries. Research investigations have focused primarily on the relative effectiveness of various dispatching rules in job shops. These rules operate by prioritizing jobs using a “criticality index” based on job and system status. Jobs are then scheduled from most critical to least, with the indexes typically being updated as the system changes.This study considers two important issues which have not been addressed previously in the literature. First, we investigate the impact of unequal machine workloads on the relative effectiveness of dispatching rules. This is significant because workloads are likely to be unbalanced in most real systems. While it is clear, intuitively, that this imbalance in machine workloads is likely to deteriorate system performance, it is not obvious whether the superiority of certain dispatching rules established in earlier studies for balanced workloads is carried forward to this case. We show that the performance of different dispatching rules does indeed depend upon the degree of workload imbalance. We also propose and test a scheduling procedure which performs well in both balanced and unbalanced systems.Next, we develop a scheduling approach which shows promise as being an improved alternative to the use of dispatching rules. This approach decomposes the dynamic scheduling problem into a series of static problems.These static problems are then solved using an optimum‐seeking method, and the solutions are implemented on a rolling basis. We show through a simulation experiment that adopting this approach over dispatching rules leads to an improvement in the overall solution quality, even in a dynamic environment.The two very practical implications of our study are: (1) that commonly used dispatching rules in job shops or automated manufacturing systems may not be the best approach when capacity utilization is unbalanced (2) a job shop or automated manufacturing system would likely benefit from implementing optimal‐seeking scheduling rules instead of the traditional job dispatching rules.

Time completion for various dispatching rules in job shops

This study investigates the relative priority of various job shop dispatching rules for various shop utilization levels under both deterministic and stochastic assumptions with regard to processing times. The primary criterion for evaluation is that of percentage on time completion. The results indicate that an assumption of accurately predetermining actual operation times in most cases is not likely to weaken the analysis and impact of research studies which are performed using such an assumption. Also conclusions indicate that the ranking of dispatching rules according to their effectiveness varies significantly with shop utilization levels.

Priority Update Intervals and Anomalies in Dynamic Ratio Type Job Shop Scheduling Rules

Dynamic priority dispatching rules in job shops require the computation of all job priorities in a work center queue every time a machine in the work center becomes idle. This is extremely costly. Alternative priority update procedures are studied and comparative results in terms of performance measures and costs are reported. Ease of implementation of the various procedures in a real world job shop environment is discussed. A second problem related to an anomaly in ratio type dynamic priority rules is also studied; a simple modification to remove the anomaly is suggested and the performances of the “old” and “modified” procedures are compared.

Priority dispatching rules in job shops with assembly operations and random delays

The article reports the results of an experimental investigation into priority dispatching rules for a job shop with assembly operations. A job is made up of several parts, where parts are individual entities requiring several operations in different machine centres. The study was directed towards rules which attempt to co-ordinate the completion time of parts required in the same job. This mainly involves rules that utilise job status information such as operation float, number of parts completed, and number of operations remaining on each part. Results indicate that job status information improves most of the measures of performance used.