Showing papers on "Job shop published in 1977"

A Methodology for Assigning Minimum Cost Due-Dates

Abstract: This paper presents and illustrates a methodology for estimating minimum cost due-dates in a job shop production system. Simulation of a hypothetical dual-constrained job shop is used to derive response measures of shop performance for various dispatching, labor assignment and due-date assignment rules. Multiple linear and nonlinear regression is used to estimate the relationship between the response measures and the value of K, the multiple of total processing time employed in assigning due-dates, for various dispatching-labor assignment operating policies. Five response measures are used as dependent variables for the regression models. They are mean job flow-time cost, mean job lateness cost, mean job earliness cost, mean job due-date cost, and mean labor transfer cost. The coefficients of the regression analysis are employed to predict shop performance in terms of the five component cost measures for varying levels of K given the dispatching-labor assignment operating policy. The estimated relationshi...

Optimal reject allowance with constant marginal production efficiency

Abstract: A job shop must fulfill an order for N good items. Production is conducted in “lots,” and the number of good items in a lot can be accurately determined only after production of that lot is completed. If the number of good items falls short of the outstanding order, the shop must produce further lots, as necessary. Processes with “constant marginal production efficiency” are investigated. The revealed structure allows efficient exact computation of optimal policy. The resulting minimal cost exhibits a consistent (but not universal) pattern whereby higher quality of production is advantageous even at proportionately higher marginal cost.

Centralized Scheduling and Priority Implementation Heuristics for a Dynamic Job Shop Model

Abstract: The problem considered is the scheduling of a job shop with job due dates, intermittent job arrivals, and statistical processing times. Centralized scheduling uses a sequence of static problems for generating priorities at review times. A multi-pass heuristic program, which has proven effective in earlier research, is applied to the up-dated static scheduling problem at each review time. A procedure is proposed for implementing priorities on the shop floor between review times. The procedure is expressly designed to integrate the scheduling of newly arriving jobs to modify the schedule. In simulation experiments using tardiness statistics for evaluation, centralized scheduling and the proposed implementation procedure proved to be an extremely effective combination. Comparison with another procedure that gives the centralized schedule precedence over new arrivals indicates the importance of the implementation procedure when periodic centralized scheduling is used in a dynamic situation.

Note---A Comparison of Capacity Planning Techniques in a Job Shop Control System

Abstract: A quantitative comparison between three types of capacity planning or shop loading techniques is presented. The results were obtained from simulation experiments.

An instructable production system: basic design issues

Abstract: The full advantages of the incremental properties of production systems have yet to be exploited on a large scale. A promising vehicle for this is the task of instructing a system to solve problems in a complex domain. For this, it is important to express the instruction in a language similar to natural language and without detailed knowledge of the inner structure of the system. Instruction and close interaction with the system as it behaves are preferred over a longer feedback loop with more independent learning by the system. The domain is initially an abstract job shop. The beginning system has capabilities for solving problems,, processing language, building productions, and interacting with the task environment. All parts of the system are subject to instruction. The main problem-solving strategy, which permeates all four system components, is based on means ends analysis and goal-subgoal search. This is coupled with an explicit representation of control knowledge. The system's behavior so far is restricted to simple environmental manipulations, a number of which must be taught before more complex tasks can be done.

A Multiple Time Series Approach to Modeling the Manufacturing Job-Shop as a Network of Queues

Abstract: The behavior of a uniformly sampled network of job-shop queues is characterized and interpreted using multiple time series. An analysis of actual queue data for a network of five functionally related machine centers shows that queue behavior is adequately described as a first order vector valued autoregressive model. This model describes the stochastic nature of each queue in the shop and its relationship to the other queues comprising the network. A network of queues obtained from simulating this job-shop under a composite dispatching rule is also modeled and interpreted as a first order, multivariate autoregressive process.

Johnson's approximate method for the 3 × n job shop problem

Abstract: The effectiveness of Johnson's Approximate Method (JAM) for the 3 × n job shop scheduling problems was examined on 1,500 test cases with n ranging from 6 to 50 and with the processing times Ai, Bi, Ci (for item i on machines A, B, C) being uniformly and normally distributed. JAM proved to be quite effective for the case Bi ⩽ max (Ai, Ci) and optimal for Bi, ⩽ min (Ai, Ci).

Man/Computer versus Automatic Scheduling

Abstract: Automatic scheduling was compared with man/computer interactive scheduling for a simulated job shop in experimental sessions. Factors of the job stream were controlled and those factors which contributed to improved man/computer scheduling versus automatic scheduling were identified. Results show that man/computer scheduling generally was superior to automatic scheduling; very significantly in several job stream situations but in one situation the automatic method was best.

The optimization of machining conditions using the center-of-gravity scheme.

Abstract: The center-of-gravity search scheme is a search strategy in which the center-of-gravity of a three point test pattern is used to establish the direction of movement with respect to the geometric center. The center-ofgravity is a weighted average of the test points in which the weighting is provided by the value of the index of performance at each test point. The geometric center is the unweighted average of the test points. The center-of-gravity method for improving machining conditions was found to be capable of determining cutting conditions which were economically superior to conditions recommended in the machinability handbooks. A procedure to apply the technique in a typical job shop environment without involving high expenditures was developed and tested on the turning, milling and drilling operations. In the experiments conducted using the above procedure, 0 to 29% cost reduction in machining was achieved on the turning, milling and drilling operations, in a relatively short period of time. The procedure was also found to be simple and easy to apply in the machine shop environment.