Distributed Supply Chain Simulation Across Enterprise
Boon Ping Gan, Li Liu, and Sanjay Jain (Gintic Institute of Manufacturing Technology) and Stephen J. Turner, Wentong Cai, and Wen-Jing Hsu (Nanyang Technological University)
The effective practice of supply chain management (SCM) is crucial to improve corporations' competitive advantage. Many corporations have built simulation models to facilitate the application of simulation in designing, evaluating, and optimizing their supply chain. Traditionally, a supply chain involves only a single enterprise with multiple facilities and distribution centers. Hence, sharing of detailed simulation models is not a problem in this scenario. But in recent years, the scope of SCM has evolved to cross the enterprise boundaries. Applying simulation in designing, evaluating, and optimizing the supply chain becomes more difficult since the participating corporations might not be willing to share their simulation models with partners. In this paper, distributed simulation techniques are presented as an enabling technology that allows corporations to construct a cross enterprise simulation while hiding model details within the enterprise. This can be realized by either building the simulation on top of the Runtime Infrastructure of the High Level Architecture or building the simulation on top of a customized distributed discrete event simulation protocol. These alternative approaches are compared in terms of their performance and interoperability. The comparison of the performance is done through a benchmarking test of a semiconductor supply chain model.
Optimal Production-Distribution Planning in Supply Chain
Management Using a Hybrid Simulation-Analytic Approach
Young Hae Lee and Sook Han Kim (Hanyang University)
Production-distribution planning is the most important part in supply chain management (SCM). To solve this planning problem, either analytic or simulation approach has been developed. However these two approaches have their own demerits in problem solving. In this paper, we propose a hybrid approach which is a specific problem solving procedure combining analytic and simulation method to solve production-distribution problems in supply chain. The machine capacity and distribution capacity constraints in the analytic model are considered as stochastic factors and adjusted by the proposed specific process according to the results from independently developed simulation model which includes general production-distribution characteristics.
A Strategic Supply Chain Simulation
James Ritchie-Dunham, Douglas J. Morrice, Judy Scott, and Edward G. Anderson (The University of Texas at Austin)
In this paper, we describe a simulation game designed to quantify the benefits of an enterprise resource planning system coupled with the balanced scorecard framework in an extended enterprise. We present three scenarios of the same enterprise: a base case scenario with a non-integrated legacy system, a scenario with an integrated, enterprise resource planning system, and a scenario with an enterprise resource planning system using the balanced scorecard framework. Results from this game support our research and teaching activities on the benefits of systems integration, data and process standardization, visibility across the business enterprise, improved decision support functionality, and operationalizing strategy.
A Methodology for Developing Robotic Workcell
Frank S. Cheng (Central Michigan University)
Robotic workcell simulation is a modeling-based problem solving approach developed for the design, analysis, and offline programming of robotic workcells. Current industrial practices show that commercial robotic simulation software packages are able to provide designers with an interactive and virtual environment in which credible solutions for robotic workcell designs can be obtained. However, conducting robotic workcell simulation studies via robotic simulation packages require designers to carry out complex processes of modeling, programming, and analysis, which often results in technical challenges and difficulties. In this paper, a methodology for developing robotic workcell simulation models via Deneb IGRIP technology is introduced. The development of the method is based on successful applications of Deneb's IGRIP robotic simulation software in designing real robotic workcells.
Using Simulation to Support Implementation of
Flexible Manufacturing Cell
Kambiz Farahmand (Texas A&M University)
A simulation model was developed and tested using Taylor II to justify the implementation of a Flexible Manufacturing Cell (FMC). The current production capacity at the existing Continuous Flow (CF) assembly line must be increased and among other proposals, a FMC is highly recommended. Simulation models are developed, tested, verified, and the model sensitivity is evaluated. The simulation models provide valuable information about performance parameters, critical elements, and bottlenecks that may appear when the line capacities have been altered. Manufacturing line evaluation and assessment of the improvements from one layout to the other is accomplished by tracking performance parameters such as lead-time, throughput, work-in process, and resource utilization. The simulation models resulted in a more in-depth understanding of manufacturing parameters and clear understanding of the improvements achieved by switching to FMC. The FMC model showed a reduction in production lead-time, average WIP, the burn-in capacity, and the number of operators required.
A Basic Study on Autonomous Characterization of Square
Array Machining Cells for Agile Manufacturing
Susumu Fujii, Hiroshi Morita, and Takeshi Tanaka (Kobe University)
In this study, a manufacturing system locating machining cells in a square array is considered as an agile manufacturing system that can cope with a variety kinds production with varying volumes. Each cell can process any work whose machining operations for each work are divided into some operation groups common to all works. An auction-based algorithm is proposed to select a cell to process a work after its processing of one operation group. Five types of bid are considered and their effects on the characterization of cells, i.e., concentration on the processing of specific work kinds and operation groups, are investigated.
Dynamic Output Analysis for Simulations of
Peter Mullarkey and Srinagesh Gavirneni (Maxager Technology, Inc.) and Douglas J. Morrice (Univeristy of Texas at Austin)
We describe the design and implementation of a generic, real-time, in-line output analysis procedure for controlling simulations of discrete manufacturing environments. We implemented this capability in the commercial simulation software Extend®. The main issues we faced were (1) Specifying the products to evaluate, (2) Determining the batch sizes for output analysis, and (3) Defining the stopping conditions based on the confidence intervals. We implemented a significance test for correlation and used this test to dynamically adjust the batch sizes used in confidence interval estimation done using batch means. When the stability conditions have been met, the simulation prompts the user to consider stopping the simulation. On the other hand, if at the end of the run length selected by the user, the statistical conditions were not satisfied, the tool notifies the user of that fact. This capability enabled us to significantly reduce the simulation run lengths, and ensures, with little additional computational effort, that the results were reliable. We used this tool to control simulations of electronics, steel, automotive, and metal processing industries. In general, using this tool we realized a reduction of more than 40% in the time required for simulation.
Ensuring the Successful Adoption of Discrete Event
Simulation in a Manufacturing Environment
J. Michael Knoll and Joseph A. Heim (Genie Industries)
Discrete event simulation has long been recognized as a valuable tool for manufacturers, but converting the recognition of value into an embrace of the technology can be a challenge. Like most technologies, with which an organization has little or no experience, timing and the manner in which simulation is introduced can significantly influence whether its adoption will succeed or fail. Without careful planning and adequate foresight, simulation technology will not prove its benefits in the workplace and will be viewed as an unnecessary expense. In this paper, we examine the characteristics that signal the need for discrete event simulation, and we discuss the strategies and methods we have found to ensure its successful adoption.
Optimizing Production Work Flow Using
John R. Clymer (California State University Fullerton)
A graphical discrete event simulation library is proposed for system simulation that is based on interacting concurrent processes. This library works with EXTEND (Imagine That Inc), an inexpensive yet capable and easy to use simulation software package, and it is called Operational Evaluation Modeling for Context-Sensitive Systems (OpEMCSS). Context-Sensitive Systems (CSS) is a systems theory, based on finite state machines, that can assist a systems engineering manager, business operations manager, or manufacturing production manager in understanding, evaluating, and optimizing production work flow, represented as communicating concurrent (parallel) processes. CSS theory can be expressed using the OpEM graphical modeling language. Thus, OpEMCSS is a graphical simulation library that can model systems based on CSS theory and the OpEM language. A simple part production problem is discussed that is an example of applying the Classifier Event Action block, which is a rule-based classifier contained in OpEMCSS, to discover optimal rules to manage the workflow.
Using Simulation Techniques for Continuous Process
Verification in Industrial System Development
Par Klingstam and Bengt-Goran Olsson (Volvo Car Corporation)
The purpose of this paper is to describe how discrete event simulation should be used as a tool for continuous process verification in industrial system development. Results include a specification of the working procedures to be used in each life cycle phase of a development project, as well as a definition of the areas where efforts are needed in the future. The approach assures continuous verification of the processes, which will lead to better decisions early on. Better decisions imply reduction in time and costs as well as systems with high quality. In conclusion, using simulation techniques for continuous process verification makes us more likely to develop an optimal industrial solution.
Using Simulation for Manufacturing Process
Reengineering - A Practical Case Study
Lisete Silva, Ana Luisa Ramos, and Pedro M. Vilarinho (Universidade de Aveiro)
This paper presents a simulation study carried out to solve a problem of manufacturing process reengineering. The specific company in which the study took place is a medium size manufacturer of chest freezers, which required an in-depth analysis of its manufacturing operations in an attempt to increase its throughput and overall productivity. A simulation model of the current manufacturing system was developed to ascertain its limitations and problems. The relevant operational performance measures were analyzed in order to allow for the proposal of a set of changes to the actual manufacturing operations. In order to support the decision process concerned with the implementation of the suggested changes, these were included in the simulation model. The outcome of the simulation study was taken into account by the decision-makers and the recommendations are being implemented.
Confident Decision Making and Improved Throughput for
Cereal Manufacturing with Simulation
Travis A. Dahl (The Model Builders) and Brian F. Jacob (Kellogg Company)
Kellogg Company faced a situation in 1999 were excess cost had to be removed from manufacturing. A significant portion of production had to be made relocated. Simulation played an important roll in two facets of this project. First, it helped identify if the proposed engineering changes would pick up the slack in production lost from relocations. Secondly, simulation was used to develop line management set points for increasing the output from the capacity installed.
Simulation Based Comparison of Semiconductor AMHS
Alternatives: Continuous Flow vs. Overhead Monorail
Igor Paprotny, Jiun-Yan Shiau, Yo Huh, and Gerald T. Mackulak (Arizona State University)
Automation is an essential component in modern semiconductor manufacturing. As factories migrate to 300mm technology, automated handling becomes increasingly important for a variety of ergonomic, safety, and yield considerations. Traditional semiconductor AMH systems such as the Overhead Monorail Vehicle (OMV) or Overhead Hoist, can however be prohibitively expensive. Cost projections for a 300mm inter/intrabay AMHS installation are in the range of $50M - $100M. As an alternative, a lower cost AMHS, called Continuous Flow Transport has been proposed. The CFT system is similar in structure to what has historically been identified as a conveyor based movement system. The CFT system provides cost savings at reduced flexibility and longer average delivery time. This study compares the CFT to Overhead Monorail transport to determine a cumulative delivery time distribution. As expected, the CFT system requires a longer average delivery time interval than OMV but may provide total savings through reduced transport variability.
Simulation of an Evolutionary Tuned Fuzzy Dispatching
System for Automated Guided Vehicles
K. K. Tan and K. Z. Tang (National University of Singapore)
This paper presents the development and simulation of a novel Genetic Algorithm (GA) based methodology applied to optimal tuning of a fuzzy dispatching system for a fleet of automated guided vehicles in a flexible manufacturing environment. The dispatching rules are further transformed into a continuously adaptive procedure to capitalize the on-line information available from a shop floor at all times. The entire problem is simulated using MATLAB/SIMULINK. The simulation results obtained show that GA is an efficient and effective tool to achieve optimal performance for the well-known NP-complete scheduling problem.
Automated Material Handling System Traffic Control by
Means of Node Balancing
Namdar Bahri and Robert J. Gaskins (PRI Automation, Inc.)
This paper presents a logistic algorithm that improves traffic conditions in a network-like automated material handling system (AMHS). The algorithm uses a look-ahead procedure and series of nodal parameters in order to balance the flow of traffic to and from load/unload nodes. In doing so, it helps manage, distribute and allocate free AMHS vehicles more efficiently. A simulation model of the algorithm, material control system and the AMHS was developed and tested on various types of semiconductor manufacturing facility layouts. The results of the simulated algorithm demonstrate up to 30% improvement in the AMHS lot delivery time.
Simulating the Furniture Industry
Robert G. Kyle, Jr. and Christopher R. Ludka (Sim X, Inc.)
The furniture industry is operating on tighter margins and ever increasing competition. No longer are the days when one could develop a product and market it for years, if not decades. With more competition and ever changing consumer demands, manufacturers are frequently realizing the necessity to reengineer their facility to satisfy the needs of many product groups and styles. Designing facilities that recognize the need for flexibility to reduce costs requires a clear understanding of the interdependent relationships naturally occurring in complex cellular manufacturing environments. However, engineers are often left to their own inherent instincts during the design phase of a project without an analytical tool to help them assess if their assumptions are correct or not. One of the best tools available to provide correct evaluations of system interdependencies is discrete event simulation. With the use of simulation, manufacturers are able to quickly and accurately model future proposed modifications to their facilities without making costly guesses. Furthermore, if modeled correctly, the simulation model built to assess the significance of a proposed layout change can be evolved into an operational planning tool that can be utilized on a continued basis to evaluate issues such as scheduling sequences or batch sizes.
Simulation of the Remote Unit Assembly and Test: A Case
Jeff Fields, Dennis Davis, and Alfred Taylor (AT&T Wireless Services)
This paper will present a case study on the use of simulation to develop and implement an assembly line for the assembly and test of customer located telephony equipment. The simulation model was used as a tool to assist in development and integration of the assembly and test processes with a focus on capacity, material flow optimization, and equipment layout. The authors will discuss how the model affected the facilities layout, equipment specifications, and material flow.
Reducing Gauging Lead Times and Optimizing Layout
Design at GM Powertrain with 3D Workcell Simulation
Rohit A. Khanolkar (Applied Manufacturing Technologies, Inc.)
This paper describes an application of 3D-workcell simulation for assessing feasibility of a concept Powertrain gauging process. It provides a basic introduction to 3D-Workcell simulation and it’s associated benefits. It describes the previous process, its limitations and problems, and also the design reviews and iterations that were performed in simulation to arrive at a new, optimized process. This new process minimizes operator handling of product and also reduces the tasks involved in completing the manual gauging operation. This paper describes how 3D-Workcell simulation was instrumental in identifying design and layout flaws prior to equipment build and install.
Scheduling Flow-Shops with Limited Buffer
Michael X. Weng (University of South Florida)
The work described in this paper attempts to validate the implicit assumption in traditional flow shop scheduling research that there is a buffer of infinite capacity between any two adjacent machines. The modified NEH (Nawaz, Encore and Ham) algorithm is used to generate an initial permutation schedule which is then improved by tabu search. For any given sequence, a limited equal buffer size is considered in computing job completion times. The scheduling objective is to minimize mean job flowtime. Computational results and analysis are presented. Through these simulation experiments, it was found that the improvement by tabu search can be significant and there is no need for more than 4 buffer spaces between any two adjacent machines. Future research directions are also discussed.
Look-Ahead Strategies for Controlling Batch
Operations in Industry - Overview, Comparison and
Durk-Jouke van der Zee (University of Groningen)
Batching jobs in a manufacturing system is a very common policy in most industries. Main reasons for batching are avoidance of set ups and/or facilitation of material handling. Good examples of batch wise production systems are ovens found in aircraft industry and in semiconductor manufacturing. Starting from the early nineties much research efforts have been put in constructing strategies for the dynamic control of these systems in order to reduce cycle times. Typically, these so-called "look-ahead strategies" base their scheduling decision on the information on a few near future product arrivals. In this paper we give a literature overview of the developed strategies, evaluate their performance and explore their relevance for practical situations by means of a simulation study.
An Analytical Model and an Optimal Scheduling Heuristics
for Collective Resource Management
Qiang Sun (Siebel Systems, Inc)
In the this paper, we study the problem of collective resource management. We first introduce the problem through real-world examples. Then we generalize the problem and build an analytical model using queuing theory. Based on this model, we evaluate the expected average waiting time of tasks. We present data from simulations, and compare the expected average waiting time from theoretical calculations to that from our experiments. We propose an optimal task scheduling heuristics. We conclude with a brief discussion of our future research plans.
Simulation in Daily Factory Operation: 'Setting the Line
Bogey in Augusta'
Gordon D. Rehn (Deere & Company)
The John Deere Augusta Works uses discrete event simulation in predicting assembly line output as a function of varying model and option mix quantities in daily production schedules. The most unique aspect of this application is not necessarily how it is used but who uses the model. Prior to each production day, a Union representative executes the model, and the simulation results establish the target production goal for the day. Day-to-day wages are based on the actual production attained relative to the simulated target. This paper describes the simulation tool structure designed for Augusta, and discusses the circumstances surrounding this unique simulation application. Included in the discussion are the benefits derived from the application; the critical success factors enabling its use; lessons learned in converting a simulation analysis into an operating tool; and future improvements envisioned.
Product-Mix Analysis with Discrete Event
Raid Al-Aomar (Classic Advanced Development Systems, Inc.)
Discrete Event Simulation (DES) has been used as a design and validation tool in various production and business applications. DES can also be utilized for analyzing the product-mix for production planning and scheduling. Product-mix decisions using analytical methods such as Linear Programming (LP) are usually made so that the market demand is met and the firm profit is maximized. However, the complexity and stochastic and dynamic nature of real-world production and business systems may lead to production levels that are different from those determined by analytical methods. Also, coping with the dynamic changes in the product-mix usually requires enhancing system parameters and/or process configuration. Therefore, its in some cases essential to conduct the product-mix analysis using a DES model that accounts for the complexity and stochastic and dynamic behavior of real-world systems. Utilizing DES to measure the system response to potential changes in product-mix is necessary to arrive at a flexible system configuration that is adaptable to dynamic changes in the product-mix. Therefore, the primary goals of this paper are to highlight the importance of analyzing the product-mix with DES, present a methodology for performing the analysis, and provide a case study to clarify the methodology.
Language Based Simulation Models as Management Tools
for Assembly Lines
Thomas Schulze (University of Magdeburg), Marco Schumann (Fraunhofer IFF) and Gordon D. Rehn (Deere & Company)
This paper demonstrates that despite the trend to Point & Click environments, the traditional approach of using general-purpose simulation languages is still eligible. The authors share their experiences gained from building a complex simulation using the language SLXTM. On the basis of examples from the projects, the efficient modeling features of the SLX languages are highlighted.
The Human Simulation: Resolving Manning Issues
Clyde R. Wetteland, Jeff L. Miller, and Jonathan French (Micro Analysis & Design), Kelly O'Brien (Northrop Grumman Corporation) and Daniel J. Spooner (Lockheed Martin GES)
The limitations that human operators impose on task execution are rarely integrated into simulations of complex systems, resulting in considerable loss of outcome fidelity. A discrete-event simulation tool, Micro Saint, was used to stochastically model the impact of human interactions in a comprehensive model of the next generation US Navy destroyer, DD21, to support the Blue contract competitor team. Mission essential tasks performed by a 3-operator and a 4-operator configurations were modeled during a demanding 2.5 hour land attack scenario. Estimates of utilization rate for the two configurations revealed that two of the operators were tasked more frequently during the 3-operator configuration compared to a 4-operator configuration. Workload estimates showed that Operator 2 was working with significantly increased workload for the smaller watchteam configuration. The workload for Operator 2 dropped 36% when Operator 4 was added to the mission. This over tasking likely contributed to the finding that the smaller configuration could not respond to a call for fire in support of ground forces before 179 seconds whereas the 4 operator team responded within 61 seconds. The DD21 model suggests that the small watchteam configuration might not be acceptable, particularly during missions lasting over several days.
Using Simulation to Evaluate Cargo Ship Design on the
Joseph C. Hugan (Forward Vision Services)
As part of the design of the next generation Naval Amphibious Transport Dock Ship (LPD17), simulation was used to evaluate the arrangement and flow of cargo on the ship and to integrate material flow concepts with the overall design requirements (see Figure 1). The simulation model evaluated specific cargo load out scenarios to determine if the proposed material handling systems would satisfy specific mission criteria. The simulation was developed in 3D using a common database of CAD geometry to not only evaluate the throughput and utilization of proposed systems but also to verify that those systems could operate within the confined spaces of cargo ships. The model considered factors such as cargo type and arrangement, forklift speed, turning radius, elevator size, and elevator speed. The placement of cargo was driven from external files and a rule set was developed to allow for the automatic generation of an unload sequence. This paper will focus on the construction of the model, its data file flexibility, and the results of the missions evaluated during the project. It will also discuss the role 3D simulation played in validating this model and communicating specific simulation results.
Simulation Based Design for a Shipyard
D. J. Medeiros, Mark Traband, April Tribble, and Rebekah Lepro (Penn State University) and Kenneth Fast and Daniel Williams (Electric Boat Corporation)
Discrete event simulation can be used for virtual prototyping of new manufacturing facilities. Models built for this purpose must be easy to use, flexible, and provide a realistic graphical view of the proposed system. The DESTINY project has developed models of plate processing operations to assist shipyards in modernizing their plate fabrication lines. Configuration information for a proposed line is collected via a Web interface, which then launches a program to build and execute a simulation of the system. Graphics images and statistical reports are then returned to the user via the Web interface. The approach allows rapid analysis of technology improvements and a visualization of proposed system operation.