Don T. Phillips

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.

Operational efficiency and effectiveness measurement

The accurate estimation of equipment utilization is very important in capital‐intensive industry since the identification and analysis of hidden time losses are initiated from these estimates. In this paper, a new loss classification scheme for computing the overall equipment effectiveness (OEE) is presented for capital‐intensive industry. Based on the presented loss classification scheme, a new interpretation for OEE including state analysis, relative loss analysis, lost unit analysis and product unit analysis is attempted. Presents a methodology for constructing a data collection system and developing the total productivity improvement visibility system to implement the proposed OEE and related analyses.

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.

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 ...

Control of multiproduct bulk server diffusion/oxidation processes. Part 2: Multiple servers

We investigate how knowledge of future arrivals can be used to control bulk server diffusion and oxidation processes in semiconductor manufacturing to reduce the average waiting time of lots. While past research has dealt with the control of bulk server queueing systems, only a few studies have addressed the use of knowledge of future arrivals, and those studies were limited to a single server system. We extend prior strategies for the single product-single server case to a multiple product-multiple server case, and devise a control strategy that is tested through the use of simulation. The performance of the new policy is compared to that of the optimal control strategy ignoring future arrivals (i.e., a Minimum Batch Size strategy). Results indicate that the new strategy performs well under a wide variety of circumstances. To demonstrate the control strategy performance in a realistic setting, a detailed simulation model of the diffusion area of an existing wafer fab was developed. The model was run with several start rates and the results compared to those from a Minimum Batch Size strategy. Results indicate that the new strategy performs well over a wide range of start rates.

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.

An expert system framework for machine fault diagnosis

Abstract This research focuses on two major issues related to the design, development, and implementation of machine fault diagnosis expert systems: (1) investigation of the actual cognitive process of human diagnostic experts, and (2) analysis of the current practices in the development of machine fault diagnosis expert systems. The investigation of the human diagnostic reasoning process has resulted in the abstraction and capturing of the human ability to learn, understand, and diagnose different machinery belonging to a particular class. The captured abstraction of human diagnostic expertise have been integrated with the expert system development expertise of knowledge engineers to provide a customized expert system shell for developing machine fault diagnosis expert systems. The designed machine fault diagnosis shell reduces the development time, effort and skill making use of generalized modules for knowledge acquisition, knowledge verification, application system generation, learning, explanation, and eliminates the burden of designing and developing each application diagnosis expert system separately. The developed shell has been validated by generating a prototype fault diagnosis expert system for a Cincinnati Milacron 786 robot.

Integration of queuing network and IDEF3 for business process analysis

Purpose – The purpose of this paper is to provide a framework and prototype software to use IDEF3 descriptions as a knowledge base from which a queuing network (QN) analysis is performed to compute system performance measures as part of quick response manufacturing. This intends to help domain experts obtain informative quantitative performance measures such as resource utilization, waiting time, and cycle time without relying on a time consuming simulation approach.Design/methodology/approach – A general open queuing network is used to extract the related resource information from the process knowledge captured by IDEF3 method. The relational database is used to integrate the open QN and IDEF3, which also improves the knowledge reusability. In addition, the performance of the open queuing network analyzer (QNA) is compared to the simulation through case studies.Findings – The domain experts usually do not own much technical modeling knowledge. However, through this integration, it is found that they coul...

Effective cost modeling on the factory floor: Taking simulation to the bottom line

A discussion on the effective implementation of cost modeling methodologies on the factory floor is presented. The target audience is industrial and manufacturing engineers who are experienced in simulation modeling and are familiar with manufacturing cost issues. The authors present a wide spectrum of viewpoints which reflect a belief that activity-based product costing more accurately reflects true manufacturing costs than traditional accounting methods. It is pointed out that indirect costs should also be proportioned to products according to burden/activities rather than product mix or other similar indicators.<<ETX>>