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Showing papers on "Job shop published in 1968"


Journal ArticleDOI
TL;DR: The study described in this paper involved a simulation of a hypothetical shop with several machines and a number of alternative rules and variations on the SI rule were investigated.
Abstract: SUMMARY A job shop is defined as a production centre consisting of several machines, each of which may be required for processing jobs of different makeups. The scheduling problem is concerned with determining the sequence in which these jobs should be processed on each machine, and this has led to several studies of alternative loading or priority rules. One rule, which has been found to be effective in reducing the average throughput time of jobs, is the SI rule, which can be described as follows: of jobs waiting in a queue to be processed on any given machine, select first the one with the shortest imminent processing time. The study described in this paper involved a simulation of a hypothetical shop with several machines. A number of alternative rules and variations on the SI rule were investigated. One modification of the SI rule called for the creation of two queues, one having a priority over the other and each queue involving an SI discipline. The decision as to which queue a job should belong to...

58 citations


Journal ArticleDOI
TL;DR: In those cases where management is already using an EOQ method for determining lot release sizes, the input data and system required for the implementation of ELRS is basically similar and therefore the new and improved analysis can be substituted at relatively minor inconvenience to the user.
Abstract: A new model ELRS for determining optimal job-shop lot sizes is presented. Since the setting of the lot release size is one of the most important controlling parameters in the scheduling of a job-shop, the improvement in technique described in the article should result in substantial savings to job-shop operation costs. In those cases where management is already using an EOQ method for determining lot release sizes, the input data and system required for the implementation of ELRS is basically similar and therefore the new and improved analysis can be substituted at relatively minor inconvenience to the user. For those job-shops which set lot release sizes by informal means, the ELRS concept may provide enough of an improved technique to induce this use of this analysis.

30 citations


Journal ArticleDOI
Robert G. Brown1
TL;DR: A flexible simulation system has been designed to permit investigation of sequencing rules in a large job shop, with continual input of new work, to understand what happens rather than to find optimum rules.
Abstract: A flexible simulation system has been designed to permit investigation of sequencing rules in a large job shop, with continual input of new work. The objective is to understand what happens rather than to find optimum rules, with many conflicting measures of effectiveness: work in process, finished goods investment, delays, machine and labor utilization, and effort to implement. A few problem areas have been explored.

13 citations


DOI
Ronald G. Pettit1
02 Dec 1968
TL;DR: In this article, a job shop is defined as having the following characteristics: 1) there is a set of production or service facilities; 2) jobs consisting of several tasks move between facilities for service; 3) one or more tasks are performed at each facility; 4) the service time for tasks may vary from job to job.
Abstract: The primary purpose of this paper is to introduce the audience to a concept that is not always appreciated by those skilled in the art of simulation. In contrast to the traditional use of simulation as a study tool, the following discussion will emphasize the potential role of simulation for operational production scheduling in job shop-like environments rather than the research-oriented role now primarily assigned to it.Simulation techniques have been employed to study nearly all phases of the manufacturing process including forecasting, long-range planning, order release, and the flow of jobs on the production floor. This paper discusses production floor scheduling of discrete production facilities with job shop characteristics. A job shop is defined as having the following characteristics: 1)there is a set of production or service facilities; 2) jobs consisting of several tasks move between facilities for service; 3) one or more tasks are performed at each facility; 4) the service time for tasks may vary from job to job; and 5) the routing between facilities may vary from job to job.

3 citations


DOI
S. Yagil1
02 Dec 1968
TL;DR: The GPSS/360 model constructed simulates both the management's supervisory decision process as well as the resulting activity of machine readable material preparation and produces a suggested equipment installation schedule.
Abstract: A computer program library is essentially a “job shop” which accepts and processes requests for computer programs. Such processing usually results in an initial delivery of the program package to the requestor, followed later by deliveries of maintenance packages to him.Packages usually consist of documentation and machine readable material (cards, tapes, disks, etc.).The latter is prepared on data processing equipment installed in the shop.Simulation of this preparation process has proved to be a useful tool in the short and long range planning of the shop's facilities.The GPSS/360 model constructed simulates both the management's supervisory decision process as well as the resulting activity of machine readable material preparation. It produces a suggested equipment installation schedule, accompanied by statistics on equipment utilization, service times, costs, etc. based on that schedule.

1 citations


DOI
02 Dec 1968
TL;DR: In this article, a simulation of the taxi service system of the University of California Lawrence Radiation Laboratory (UCLRL) was undertaken to investigate (without disrupting normal operations) ways of modifying the operations of the existing system which would result in substantially better service at no great additional cost.
Abstract: A simulation of the taxi service system of the University of California Lawrence Radiation Laboratory (UCLRL) was undertaken to investigate (without disrupting normal operations) ways of modifying the operations of the existing system which would result in substantially better service at no great additional cost. The successful achievement of the above objective resulted from the recognition of the close relationship between job shop scheduling and the decision-making problem of UCLRL's taxi service system; and the applicability, therefore, of some of the rules and heuristics employed in job-shop scheduling. GPSS III was used to model the proposed system, rules and heuristics because it readily permitted the formulating of complex models. Although GPSS flexibility allowed accurate modeling of the majority of the system, GPSS approximations were still necessary to represent the distribution of arrivals. To defend the independent Poisson distribution a statistical inference study was used to establish that the model's distribution was robust with respect to the effects of the actual distribution of arrivals.A brief description of UCLRL is necessary prior to any further discussion of how the simulation study was particularly applied.

1 citations


DOI
02 Dec 1968
TL;DR: This is a state-of-the-art paper illustrating the approach to an old problem using a relatively new capability, GPSS/360, and the models shown here are remarkably compact in comparison with earlier simulation models used to investigate the same or similar scheduling rules.
Abstract: Pertinent characteristics of the job shop scheduling problem are reviewed. Two GPSS/360 models assessing a total of eight alternative rules for constructing job shop schedules are presented. These rules have been studied by earlier investigators; hence this is a state-of-the-art paper illustrating the approach to an old problem using a relatively new capability, GPSS/360. Selected model output is exhibited, results are summarized, and assembly and execution times are indicated. Several references to appropriate earlier investigations are included. The models shown here are remarkably compact in comparison with earlier simulation models used to investigate the same or similar scheduling rules.