Gary L. Hogg

A state-of-the-art survey of dispatching rules for manufacturing job shop operations

Abstract This paper reviews recent studies of dispatching rules. A dispatching rule is used to select the next job to be processed from a set of jobs awaiting service. The paper has two objectives. The first is to discuss the state of the art in the study of dispatching rules. The discussion includes analytical approaches, simulation techniques and evaluation criteria. The second objective of the paper is to compare several of the dispatching rules listed in the Appendix using the results of recently published studies. It is impossible to identify any single rule as the best in all circumstances. However, several rules have been identified as exhibiting good performance in general.

A comparison of order release strategies in production control systems

SUMMARY This research investigates the performance of four order release strategies for use in production control. Two of these strategies, the constant work-in-process (WIP) and the bottleneck strategies, are developed with the use of characteristic curves which define the relationship between WIP and rate of production. A third strategy matches order releases to those orders completing production over prior time periods. The fourth strategy fixes order release at a desired level of production output. All strategies were simulated over a range of shop conditions. Results demonstrate that both the constant-WIP and bottleneck strategies are stronger performers.

Real-time tool control and job dispatching in flexible manufacturing systems

A method of loading a set of tools to the different machining centres of a shop is presented, where each part visits only one of the machining centres for its entire processing. Any tools which are required but unavailable for the processing of a part are borrowed from other machining centres. As a real-time control, the tool-returning policies for those borrowed tools and the job-dispatching rules at the machining centres are evaluated to maximize the throughput performance of the shop. Some experimental results are provided.

A review of graph theory application to the facilities layout problem

In this paper, the application of graph theory to the facilities layout problem is reviewed. The basic concepts of the approach, and its similarities and differences with respect to current approaches are examined. Previous and current work in this area is presented in a unified framework to aid in understanding the concepts and methodologies employed. The paper concludes with an evaluation of this relatively new tool, considers its limitations, and provides suggestions for research.

CONTROL OF MULTIPRODUCT BULK SERVICE DIFFUSION/OXIDATION PROCESSES

This paper demonstrates how knowledge of future arrivals can be used to control bulk service diffusion and oxidation processes. The objective of the research reported herein is to reduce the average time that lots spend waiting to be processed. A review of the current literature reveals that several researchers have dealt with the control of bulk service queueing systems; however, only one has addressed the use of knowledge of future arrivals and it only considered the case of a single product and a single server. This research reexamines the single product-single server case, and men explores the multiple products-single server case. For both cases, a control strategy is devised and evaluated through the use of systems simulation. The steady-state performance of each control strategy is then compared to the steady-state performance of the theoretical optimal control strategy not considering the timing of any future arrivals (i.e. a Minimum Batch Size strategy). The experimental results indicate that the ...

UNCONSTRAINED DISCRETE NONLINEAR PROGRAMMING

In this research several search methods for unconstrained nonlinear discrete variable optimization problems have been developed. Many of these new methods are modifications of effective continuous variable search techniques including gradient–free and gradient–based methods. In order to search only over a set of discrete points, the concepts of integer search direction and the subsequential search procedure are introduced. Other developments include regeneration/ acceleration procedures for gradient–based methods and a second level acceleration procedure applicable to both gradient–free and gradient–based methods. These new methods have been compared with each other and existing techniques using test problems with various characteristics, including penalty functions from constrained problems. In all cases, the best results have been obtained from one of the new methods. Moreover, the success of these new methods in finding good solutions in penalty function problems indicates their usefulness in solving e...

On constructing a block layout by graph theory

This paper examines the problem of developing block layouts using graph theory. It is shown that there are several limitations associated with such layouts, particularly when facility relationships are represented quantitatively by a from-to chart. A modification to conventional construction-type layout procedures is presented which allows a graph theoretic block layout to be developed, regardless of the type of facility relationships used, and without performing all the steps required in the graph theoretic approach. This new method helps to avoid the limitations of the approach and alleviate its computational burden.

A construction algorithm for the selection and assignment of materials handling equipment

A model for selecting materials handling equipment and assigning it to departmental moves is presented. The problem is formulated as an integer program with the objective of minimizing the total operating and investment costs of the selected equipment. The constraints specify that each move is restricted to only one equipment type and the available operating time of each equipment type cannot be exceeded. The problem is solved using a construction heuristic algorithm that exploits, conceptually, some similarities to both the knapsack and the loading problems. The algorithm is computationally attractive and lends to achieve other goals, such as maximizing equipment utilization and minimizing the variations in equipment types, as well as the primary goal of cost minimization.

A two-list synchronization procedure for discrete event simulation

The traditional mechanism for maintaining a list of pending events in a discrete event simulation is the simple linked list. However, in large scale simulations this list often becomes cumbersome to maintain since the number of pending events may become quite large. As a result, the execution time required by the simple linked list is often a significant portion of total simulation time. Several papers have been published suggesting improved synchronization procedures. The most efficient procedures reported are the time-indexed procedure and the two-level procedure. Both methodologies are much more efficient than simple linked lists; however, neither has been adopted by a general purpose simulation language. Further, both procedures require external parameter definition, which is a major handicap to their adoption by a general purpose language. This paper introduces a new sychronization procedure, the two-list procedure, which is much faster than simple linked lists for large pending event files. This procedure was designed for implementation in Fortran, and properly implemented it is transparent to the user. Thus it is ideal for adoption by general purpose simulation languages.

Parallel-Channel, Dual-Resource Constrained Queueing Systems with Heterogeneous Resources

Abstract This paper presents an analysis of a class of multi-resource constrained queueing systems. The systems are “job-shop” queueing systems where both machines and laborers are limiting resources. The model consists of M parallel channels, each containing a single machine. Each service channel has its own queue in which an FCFS discipline is enforced. Arrivals to the system are Poisson and are randomly assigned to a specific service channel upon arrival. The labor force consists of N laborers (N < M) who are not equally skilled; thus, the processing time (exponential) is dependent upon the laborer and machine center utilized. Two different means of allocating labor to competing jobs are considered: (1) a first-in-first-out rule, and (2) a maximum laborer efficiency rule. The emphasis of the analysis is on the effects of the pattern of heterogeneity of the labor force and method of labor allocation. GERTS QR, a stochastic network simulation model, is utilized as a vehicle of analysis.