1. An overview of material engineering logistics concepts

2. Application of static simulation methods

3. Application of dynamic simulation methods

4. Discussion of static and dynamic simulation as complimentary engineering analysis tools

5. Brief overviews of several unique applications of simulation in material engineering tasks

Overview of Material Engineering Logistics
Material engineering logistics refers to a variety of tasks associated with the transportation and distribution of parts and containers throughout the manufacturing environment. Most often this refers to mobile equipment such as fork trucks, tow trains, tractor trailers, and even the human operator. Material handling analysis is often focused within the production facility, but recently, it is addressing trailer traffic yard management and material transportation between "nodes" of the supply chain. Material handling analysis is not limited to material flow simulation. We use static simulation to evaluate many aspects of material logistics, such as:

• Receiving dock locations and congestion,

• Material storage locations and configuration,

• Material replenishment methods, and

• Part containerization specifications.

The overall objective of material engineering logistics is forward planning. Planning for new production programs, facility modifications, or improvement opportunities within existing operations.

Application of Static Simulation
Static Simulation provides a "snapshot" model of activity. It is an "averaged" result over the model time period. For example, a model of fork truck activity would provide results such as total travel time, total travel distance, and total material moves per day.

The static simulation tool (FactoryFlow) can provide a graphical representation of the material flow model. This graphical output supports communication and presentation of material handling requirements and provides visual proof of layout and material handling improvement.

A static simulation model that is used as an integral part of the manufacturing planning effort allows an engineering team to keep in mind aspects of material flow, layout development, and material containerization. The model may be modified quickly for iterative analysis of alternatives.

As the production plan and data becomes more detailed, the material flow model becomes more detailed to provide finer results. This detailed production plan and supporting data supports evolution into a dynamic simulation model.

Application of Dynamic Simulation
Dynamic simulation provides a representation of a system or activity over a period of time. This helps to analyze the impact of variation to system characteristics on a specified activity. These variations include not only the average or typical condition but also the "peaks and valleys" for a particular characteristic.

Dynamic simulation provides insight into the interaction between activities in a particular system. For example, the simulation model can help to analyze the impact of random trailer arrivals on one or a group of fork trucks.

The dynamic simulation tool consists of a series of generic modules (developed by Design Systems, Inc.) which can be quickly customized to represent most any environment for material flow. These generic modules were created using the AutoMod simulation software. The modules are highly data driven and provide a "to scale" 3-D animation of the system or activity under study. Typical module types currently used in material flow studies are:

• Part delivery from storage to line using tugger/ trailer route system

• Part delivery from storage to line using fork trucks

• Part delivery from dock to line using fork trucks

• Inbound and on-site trailer management

These generic modules generate custom reports which track various system performance measures. These reports allow the engineer to compare various alternatives.

The animation of the dynamic model is a useful tool to visually present and analyze various system configurations to management and production personnel.

Historically, dynamic simulation has been used in the final stages of a study due to the up front model development cost and the time required to modify the model to reflect system design changes or "what if" scenarios. Modularized dynamic simulation model development minimizes the investment required to develop a baseline mode. This leaves more time available for actual material flow engineering analysis.

Static versus Dynamic Simulation
Static Simulation provides reliable results for material engineering planning; however, the results are an "averaged" result. The engineer applying static modeling must keep this in mind. An averaged result cannot take into account "peaks and valleys" of material handling requirements, and it cannot demonstrate real-world, dynamic interaction and inefficiency.

Through many years of experience, we have found that a combination of both Static and Dynamic Simulation modeling offers the best, complete material handling analysis. Static simulation generates fast, iterative, macro level results; dynamic simulation offers a more detailed analysis for areas that pose higher variability or may have significant cost impacts.

In most cases, Static Simulation may be used early in production and material handling planning. The static model is a good tool to analyze the entire production facility and identify areas that could benefit from a detailed Dynamic Simulation analysis.

The dynamic model allows the engineer to "fine-tune" areas of high material handling traffic, high frequency of moves, or costly material handling requirements. In addition, the dynamic model is a very good training or communication tool to display proper material handling methods to the production facility and management.

Case Studies
To demonstrate the various uses and results of static and dynamic simulation analysis, the presentation reviews several real-world applications.

Dock to Line Analysis for High Use/Sequenced Commodities
A static simulation model may highlight a specific commodity that, compared to other commodities, requires excessive material handling resources.

The static analysis will generate results such as average travel distances and times, but it cannot take into consideration of delays due to random trailer arrivals, aisle congestion, or unavailability of material handling device resources. In the case where delivery of a commodity to the line is a critical operation, the material handling plan must evaluate the likelihood of not satisfying the material replenishment requirement; thus the application of the dynamic simulation analysis.

The dynamic model includes these dynamic variations to the material handling system, and can evaluate the risk associated with these variations. In general, the dynamic simulation model is used to evaluate and compare various system characteristics such as:

• Number of fork trucks required

• Fork truck work assignments

• Route for material delivery line side

• Evaluate dock requirements and management

• Empty container management

• Marshaling and storage requirements