Paul Savory

A simulation-based experiment for comparing AMHS performance in a semiconductor fabrication facility

As the cost and complexity of constructing a semiconductor fabrication facility increases, responsive tools are needed for designing and planning its operations. Discrete-event simulation paired with design of experiments is an effective combination. This article demonstrates how simulation in combination with design of experiments is used to compare the intrabay layout of two automated material handling systems. The difference in stocker robot utilization, number of vehicle moves per hour, and average delivery time for the two intrabay layouts will be compared using a fractional factorial experimental design. The study demonstrates that the distributed storage option is preferable for maximizing manufacturing performance. The solution procedure has general applicability as a tutorial for practitioners.

Ascertaining Important Features For Industrial Simulation Environments

Recent years have witnessed the development and commercial release of multiple simulation tools, environments, and intelligent simulators. Each release seems to contain additional advanced features designed to simplify simulation use and increase the productivity of model builders. But to date, no one has addressed feature definition from the viewpoint of a simulation practitioner. This paper discusses our efforts to identify and prioritize simulation features deemed most desirable from the practitioner viewpoint. A series of three questionnaires was developed and administered to a group of qualified simulation practitioners. With results that are of interest to simulation users, researchers, and simulation software developers, the survey responses reveal not only what practitioners feel are the most important features of presently available commercial packages, but also identify important areas for future development.

A template-based conceptual modeling infrastructure for simulation of physical security systems

Although simulation is one of the most innovative and cost-effective tools for modeling and analyzing a system, simulation studies often fail to provide any useful results. One reason is attributed to the fact that model formulation depends on the skills of the analyst. This paper describes a research to develop a conceptual modeling infrastructure to assist a simulation analyst in specifying components for studying physical security systems. The modeling framework has been programmed as an Internet-based Web application. Using the application, the successful development and implementation of a physical security simulation model will be aided by a defined scientific methodology rather than simply the skills of the analyst. Further the modeling framework is simulation language independent, thus allowing for a top-down or bottom-up approach to developing the conceptual model. This offers support for an object-oriented modeling design.

A Web-based interface for storing and executing simulation models

The dominance of the Internet in the development of information and communication technology has made Web-based distributed solutions increasingly attractive. Apart from providing other services, the World Wide Web is being looked upon as an environment for hosting modeling and simulation applications. SIMAN is a simulation language that allows users to simulate discrete and continuous systems. In this research, a Web-based interface or toolkit has been developed for storing and executing SIMAN simulation models over the Internet. This toolkit consists of a World Wide Web interface to SIMAN and a Web-accessible database for storing user models. It provides users an easy-to-use environment for developing text-based simulation models using the SIMAN simulation language. It also allows users to test the functionality of a SIMAN model using the SIMAN debugger/run controller.

Integrating simulation with activity-based management to evaluate manufacturing cell part sequencing

Abstract This paper presents an integrated simulation and activity-based management approach for determining the best sequencing scheme for processing a part family through a manufacturing cell. The integration is illustrated on a loop or U-shaped manufacturing cell and a part family consisting of four part types (A, B, C, and D). Production requirements for the cell demand that part batches be processed one type at a time. For example, all part A’s are processed until weekly demand is met, then part B’s, etc. The objective of this example is to determine the best part sequence (e.g., ABCD, DCBA or CABD). In addition to traditional measures, the simulation model produces detailed activity-based costing estimates. Analysis of cost and performance parameters that indicates part sequence CDBA provides the best overall choice. This sequence achieves a low per unit manufacturing cost, minimizes average time in the system and in-cell inventory cost, and maximizes unused production capacity. Although the scope of this effort was restricted to a small scale manufacturing cell, the costing concepts have general applicability to manufacturing operations at all levels.

Operations research methods applied to workflow in a medical records department.

Transcribing medical documents accurately into pre-defined formats and within certain time frames is vital for administrative and medical purposes in any hospital. This paper describes quantitative models incorporating available data to represent transcription activities of a medical records department. We forecasted the workload of the department, determined the optimal worker schedule and designed a simulation model to represent the workflow of the transcription function of a medical record department. The findings provided insight into the workflow, staffing and performance of the department.

Using Mathematica to aid simulation analysis

As computer power has increased, so has the capability of software developers to write programs that assist people with time-consuming tasks. Mathematica is such a program. The objective of this paper is to demonstrate how Mathematica, a symbolic programming environment, can be used to aid simulation analysis. In addition to a general discussion of Mathematicas uses, advantages, and disadvantages, several examples are presented. The examples include using Mathematica for distribution fitting, queueing analysis, random number generation, and creating a surface plot for optimization.

Combining Activity-Based Costing with the Simulation of a Cellular Manufacturing System

Abstract Discrete-event simulation is one of the most effective techniques for analyzing a manufacturing system. Unfortunately, little attention is given to using simulation models to estimate the economic impact of a proposed system configuration. This paper defines how activity-based costing (ABC) concepts can be incorporated into a discrete-event simulation model. Special emphasis is on demonstrating how decision making can be aided by having the simulation create a detailed “Bill of Activity” describing costs associated with manufacturing a part. The integration of ABC and simulation is illustrated by evaluating the impact of a proposed manufacturing cell configuration. The additional costing information aids in cell design, determining part sequencing and scheduling, and provides a quick evaluation of product mix changes for a part family.

An aggregation procedure for simulating manufacturing flow line models

We develop a formal method for specifying an aggregate discrete-event simulation model of a production flow line manufacturing system. The methodology operates by aggregating production stations or resources of a flow line. Determining the specifications for representing the aggregated resources in a simulation model is the focus of our presentation. We test the methodology for a set of flow lines with exponentially distributed arrival and service times. Comparisons between analytical and simulation results indicate the aggregation approach is quite accurate for estimating average part cycle time.

A template-based data specification framework for modeling physical security systems

Simulation studies often fail to provide any useful result due to its success being highly dependent on the skills of the analyst to understand a system and then correctly identify all the required data parameters and dependent variables. This paper describes a template-based framework to help identify and specify the components and data parameters for developing models of physical security systems. The layered framework consists of 15 templates built on top of 14 data primitives representing 119 data parameters. The modeling framework has been programmed as an internet-based web application and is simulation language-independent. The usefulness of the framework was tested and shown to have a significant impact on improving the identification of system components and their associated data parameters.