Simulation: The Real Story

Simulation software used to focus on getting materials handling systems to run properly. Now features are functions are pushing simulation into the operational aspects of factory automation.


There’s much to understand about factory simulation software and its capabilities, which include how to determine plant capacity, balance manufacturing lines, manage bottlenecks, solve inventory and work-in-process problems, test new scheduling practices, justify capital expenditures, and optimize production rates, says Bill Nordgren, president of Enterprise Dynamics (formerly F&H Simulations; Orem, UT). Yet most users of simulation software use it on a project basis. They build a model of, say, a production line, solve their problems, and then move on. Later, if a problem arises, often so many changes have been made to the actual production line since the model was built that the existing model has to be greatly revised or a new model has to be rebuilt from scratch.

That’s changing. The trend nowadays, continues Nordgren, is to make simulation an integral and very much a visual and animated part of a company’s operational database for daily scheduling, production analysis, and troubleshooting. This is why simulation software over the years has acquired a diverse set of features, such as virtual reality (VR), object-oriented (OO) methods, database links, and the ability to emulate plant-floor control systems and data acquisition equipment, as well as actually run and gather inputs from them.

This is consistent with the overall trend, explains Peter Schmitt, vice president of Marketing and Business Development for Delmia Corp. (Troy, MI), of integrating simulation applications not only to themselves but to other applications as well, including enterprise software,


Options for Integration

Two companies pushing integrated simulation are Tecnomatix (Nashua, NH) and Delmia. Tecnomatix’s eMPower applications create a collaborative factory-oriented planning and design environment based on simulation and analysis. In operation, eMPower applications are used to create an “electronic bill of process” (eBOP), the manufacturing equivalent of a bill of materials (BOM). eBOPs describe all of the parts, resources, operations—and the relationships between those elements—to produce a product. Basically, eBOPs are objects—small software “packages”—that contain all the information related to a particular product. eBOPs are stored on the eMServer, where they can be accessed, used, and modified throughout the extended enterprise. Up to now, these objects were contained in an ObjectStore database from Object Design Inc. (Burlington, MA); now, eMServer can run on an Oracle database.

In a similar vein, Delmia’s PPR Hub for Manufacturing is addressing product, process, and resource (PPR). The PPR Hub shows how these three aspects are related and what their dependencies are. Delmia’s reasoning is as follows: “PDM systems normally take care of only the product data. They have no way to describe processes in detail, nor to store processes in terms of times, human resources, automated resources, and so on,” says Schmitt. Delmia’s strategy is to combine its conventional PDM system, namely Enovia’s VPN, with the PPR. (PPR Hub is an intermediate step. Eventually, it will be merged into VPN.)

PPR Hub is a repository for data. The product data includes the product structure of the eBOM and the geometry and attribute data in the CAD master model for the product. The eBOM can reside in the CAD or the PDM system, depending on the CAD system used. The process data is populated with the Delmia process planning, manufacturing engineering, and industrial engineering solutions. Some of the resource information may exist in plant layouts and tooling drawings. PPR Hub ties all of these data together through data linkages or pointers. 

Behind the scenes, PPR Hub for Manufacturing is a three-tier Oracle relational database that manages product structures, product variants, as well as all planning documents; provides enterprise-wide access to all planning data; and links to Delmia software through programmable application interfaces.

PPR Hub is not really a standalone product; it is an infrastructure that should be implemented when two or more Delmia products are installed. PPR Hub, and the interoperability it provides between all of Delmia’s simulation applications, is now available in Delmia V5R7. (All of Delmia’s products are now on the same release cycle. The next release is V5R8 in February 2002; R9 will be five months later.)

How much of Tecnomatix’ eMPower and Delmia’s PPR are PowerPoint-ware? Both vendors have a long history involving a broad range of successful, standalone simulation products. Both want to move away from “point-solution sellers” and toward providing complete “end-to-end solutions” that go beyond simulation and well into process planning, factory design, and production monitoring.

However, both vendors have very different data repository philosophies, as well as differences in how production planning is documented. One vendor focuses on its eBOPs; the other, on its eBOMs. Asks Zvi Feuer, vice president for Automotive for Tecnomatix Technologies, Ltd. (Herzeliya, Israel), “Can a PDM system really describe a process?” Tecnomatix doesn’t think that’s possible. “There’s a big difference in the way you manage and maintain the product tree and the way you manage and maintain the process tree.” To lend credence to that, Feuer recalls a General Motors’ estimate that each item in a product design is associated with a thousand items in the process and 10,000 items on the shop floor.


The “Atomic” Approach

While Tecnomatix now offers a conventional database infrastructure, Taylor ED from Enterprise Dynamics. (Eventually, the name of the software and the company name will be the same: Enterprise Dynamics.) Taylor ED objects are called “atoms.” Everything in Taylor ED is an atom: resources, machines, pallets, conveyors, products, people, tables—you name it—as well as the connections to other software or to itself. Explains Nordgren, “Atoms can be freely created, destroyed and moved into one another. They can have their own behavior or inherit their behavior from other atoms.” Even stereo sounds can be added to an object to make its simulation “appear” more lifelike, such as the sound of a conveyor.

All of these objects are fully customizable. Enterprise Dynamics provides the source code to over 130 objects with its software. By using the company’s atom editor, a user can modify objects and create new ones as needed.

In addition, Taylor ED can dynamically store and retrieve simulation data through its ODBC database interface, through a Microsoft DDE link with Word and Excel, or by using SQL calls from within the simulation system. Moreover, the software can communicate with remote simulation models or software applications over the Internet, as well as locally to barcode scanners and other plant-floor devices. Last, you can link your own dynamic link libraries (DLLs) to Taylor ED, which lets you use code you’ve written in the programming language of your choice.


Distinguishing Volvos from Corvettes

Brooks Automation Inc. (formerly AutoSimulations, Bountiful, UT) recently announced its Tanks & Pipes module, an extension to its AutoMod simulation system. Tanks & Pipes models liquids and bulk materials, handling batch processing as well as continuous and semi-continuous processes, liquid storage, and transport systems. The rates of material flow can be constant or dynamic. If AutoMod detects a source tank runs out or a destination tank fills, it will issue an alert. Such simulation is useful in automotive because of the paint lines on the assembly line, plus the associated storage tanks and pipe lines.

Beyond that, Brooks Automation has already mapped out the next three or so releases of AutoMod. Additional OO capabilities in the forthcoming Version 10.5 will make model reuse and connecting modeling components together easier. That release will also include OLE for Process Control (OPC), a standard protocol for communications between control systems and control devices. This standard, already in use at General Motors, becomes increasingly important as simulation systems are used for emulation, such as for control system check-out or for off-line programming.

Brooks Automation is also readying a module for modeling train-type systems. This isn’t just railroads; it’s any kind of carrier that includes an engine or some sort of primary mover, followed by a bunch of trailers. Such carriers commonly deliver parts to automotive assembly operations. Brooks is also rewriting its Power & Free System module into OO language partly to handle more complex features, such as bias banking.

In the meantime, Brooks Automation is cutting loose from Silicon Graphics platforms, the simulation hardware-of-choice for many years now. Current and future versions of AutoMod will run solely on Microsoft Windows 95/98/NT/W2K. “Users aren’t standardizing on Silicon Graphics these days; they’re standardizing on mainstream PCs,” says Matt Rohrer, director of Simulation Products for Brooks Automation. This is true for all simulation software because of the various high-speed, fabulously real, 3D rendering technologies, such as OpenInventor, that provide a raft of smooth surfaces and complex polygons in the Windows universe.

For instance, in previous versions of AutoMod, continues Rohrer, “no matter how hard users tried, the cars they modeled always looked like Volvos. Boxey.” Now with AutoMod v10.0 VR-level graphics, users can examine the model, whether a single workcell or an entire factory, from any angle and at any scale while the model is running. Better, users can tell where there’s a Corvette in the simulation.