This article focuses on the efficient planning involved in the manufacturing plant. Factory simulation software gives a sense of whether or not such a bottleneck would occur if the factory process were laid out as planned. It extrapolates problems of a particular line layout and forecasts the costs of a problem like a bottleneck. The digital factory software allows manufacturers to simulate factory layout digitally, in order to see how the plant would function under the proposed arrangement and to realize potential problems on the line. In addition to robots, employees themselves can be represented in a digitized version. In this way, engineers can figure out where employees should stand on the line and design workstations for them to both optimize their movements and to ensure they are not under any kind of ergonomic stress. Virtual factories can be planned together by people in different locations with the help of software that allows for fly-through.

## Article

Only a decade ago, it took many years for a spacecraft to move from the drawing board to the launch pad. It now takes only about two years to design and build a satellite, thanks to recent advances in computer-aided design and other technological techniques.

It used to take five to seven years before a new model car was ready for market. Today, that cycle has been shortened to two or three years. And time to market continues to drop, even as the size and the complexity of satellites and automobiles grow. Still, market pressures are pushing manufacturers for even more reductions in time to market.

Feeling that pressure, Astrium of Velizy, France, a maker of satellites and military space systems, looked recently for further ways to cut cycle times and reduce production costs. One answer came when the company implemented software that helped plan some of the factory processes via computer before they were actually implemented on the floor, said Elfred Roberts, system manager at Astrium.

The digital factory software allows manufacturers to simulate factory layout digitally, in order to see how the plant would function under the proposed arrangement and to suss out potential problems on the line.

Contrary to what it may sound like, digitizing the factory, as it's sometimes called, doesn't mean replacing all the workers in a plant with high-tech robots. Instead, the software can help ensure that a product is manufactured in the most streamlined method possible.

Digital factory software extends the uses of computer-aided design tools used by engineers for product design, said Peter Schmitt, vice president of marketing and business development at Delmia Corp. of Troy, Mich. His company is considered to be one of the major providers of software for digital factory, or virtual manufacturing, applications. Other software and hardware providers in this realm are Tecnomatix Technologies of Herzeliya, Israel; Rockwell Automation of Milwaukee, and EDS of Piano, Texas.

"Both types of software tools optimize how products can be manufactured," Schmitt said. "CAD tools help engineers take care to come up with optimal product design. But factory digitalization makes sure the product can be manufactured in the right quality with reliable processes, within the shortest time frame, and with the best factory layout."

Digital factory software is used for more than just laying out a plant floor on computer. It serves a number of functions around the manufacturing plant, including designing individual workstations in order to guard employees against repetitive motion injuries, and siting and programming the robots used on the line.

While factory simulation software lets manufacturing engineers visualize the production process via computer—which allows an overview of factory operations for a particular manufacturing job-discrete simulation lets the engineers focus up close on each individual production stop. Both views are necessary to get a complete sense of what's happening on the factory floor, Schmitt said.

Virtual manufacturing techniques have been in use for about 14 years in the automotive industry. Within the last decade they've been adopted more and more by those in the aerospace realm, said Deidra Donald, aerospace domain leader at Delmia. Some of the software modules that allow for discrete simulation are particularly useful in aerospace, she said.

"When you have a bottleneck, it's easy enough just to see that on the actual shop floor itself. The parts are queuing up in one place and not moving on to the rest of the system," she said. "But you can't see how it's impacting the overall facility or overall production. Digitally, you not only see the parts queuing up, but you can also quantify how much it's affecting you. It could be, you think it's not affecting you, but of course it could be affecting costs."

## Solving by Simulating

Factory simulation software gives a sense of whether or not such a bottleneck would occur if the factory process were laid out as planned. It extrapolates problems of a particular line layout and forecasts the costs of a problem like a bottleneck, Schmitt said.

Consider that a typical car has between 25,000 and 35,000 parts, and you get an idea of the scale and impact of the software's forecasts.

Many of the uses for digital factory software occur well before the final product is even designed. If engineers decide to change the design of a part while the part is still only a CAD model, they can use virtual factory simulation to demonstrate the effect of the new design at every stage of the manufacturing process. The redesigned part, for example, might 'need more clearance on the automotive line.

Some companies, like Arctic Cat of Thief River Falls, Minn., a maker of snowmobiles and all-terrain vehicles, use technology from a single vendor to design a product using CAD. That keeps them in touch with other engineers and suppliers involved in the project using the vendor's collaboration software, and then helps to account for the product's manufacturing with factory design software. Arctic Cat uses technology from EDS.

There are three areas to consider before actually laying out a real factory, Schmitt said. First, engineers have to determine the assemblies, fabrication, and machining needed for the specific manufacturing process. Second, they need to figure out what tooling, fixtures, and equipment-down to the nuts and bolts-will be needed. Then, they must lay out a factory floor plan. Virtual factory software is useful for each of these steps.

Schmitt pointed out that the technology is used for specific processes within broad parameters. Once engineers build a complete three-dimensional mock-up of the intended factory, for example, they can essentially turn the model on and see what happens.

"You then see the degree of stability in your process in case, say, a machine breaks down," he said.

The simulation shows how the breakdown will affect the entire line. Also, the broken machine can be further pinpointed via simulation, Schmitt said. In other words, a particular breakdown is modeled as part of the entire factory line and is also modeled via discrete event simulation. In this way, the engineers account for many eventualities.

"They'll know what strategies to take if a machine really does break down-how people will work around the problem," Schmitt said.

Virtual manufacturing software also allows engineers to simulate robotic functioning.

"For robotic simulation, you have all these discrete tools to do all of these nonhuman simulations," Schmitt said. "Can the robot reach all the points it needs to reach? That's what you look at first: rough studies without any specific detail. But you eventually decide for each robot where they should stand. And then you basically do off-line robotic programming that says, 'I want it to reach this point,' and you download that to the physical robot."

In addition to robots, employees themselves can be represented in a digitized version. In this way, engineers can figure out where employees should stand on the line and design workstations for them to both optimize their movements and to ensure they're not under any kind of ergonomic stress. Using virtual factory software, engineers can tell if an employee could reach a particular tool on the line and if the employee would be strong enough to lift it. They can see whether an employee could repeatedly perform a task without risking a repetitive-motion injury.

## Virtual Factory, Real World

DaimlerChrysler of Stuttgart, Germany, is currently digitizing the way its manufacturing plants are designed, a move expected to cost between eight and nine figures, according to executives there. Factories will be entirely simulated-inside and out, from initial floor plans to functioning assembly lines-before they're built. The key is that the investment is expected to reduce new-vehicle production cycles by up to 30 percent, an automaker's holy grail.

The entire production process will be simulated before one brick is put in place, said Susan Unger, DaimlerChrysler senior vice president and chief information officer. The company will use technology from Dassault Systemes of Paris and from Delmia for the process. The automaker will also use the technology to retrofit all of its plants under one digital factory plan.

With the software in place-expected to be by 200s-engineers can determine before production how to best place a part within a car as it travels down a line and how best to situate welds, Unger said.

The automaker first put the digital factory concept into place a year ago at an engine manufacturing plant in Koelleda, Germany. According to Unger, the plant was designed and laid out using digital factory and CAD software, which allowed the company to cut factory construction time by 30 percent and square-foot plant floor costs by more than 10 percent.

The automaker is also running a pilot program with the software to retrofit a Mercedes-Benz factory in Germany. The Toledo North assembly plant in Ohio, home of the Jeep Liberty, was the first Chrysler facility built using manufacturing simulation. Costs there were $54 per square foot, which compares to an industry average of$70 to $80 per square foot, Unger said. The digital factory concept implemented at Daimler-Chrysler aims to shorten production-planning cycles by up to 30 percent, enforce quality, and reduce costs, Unger added. DaimlerChrysler isn't the first vehicle producer to investigate virtual factory techniques. Lansing Grand River, a General Motors plant in Lansing, Mich., was designed using 3-D computer simulation. The$559 million plant employs about 1,500 people and builds 130,000 vehicles a year. It makes the new Cadillac CTS luxury sport sedan and will eventually build other luxury vehicles.

Virtual factory software allowed engineers to test how operators, tools, and material-handling systems would work together even before construction began, said Gary Cowger, vice president of GM North America. By simulating the factory on computers before building it, GM built the 1.9 million-square-foot manufacturing plant in 21 months, which Cowger said is less than half the time it normally takes to build auto plants. Simulation made it easier to identify and solve problems before they became ingrained in the construction process, he added.

"Designers were able to examine the interaction of conveyors, relationships between machinery and utility lines, and see the clearances needed for machinery," Cowger said. "Extensive testing and validation were done to ensure that production could begin with no lost production or quality defects."

## Still wishful thinking

Engelbert Westkamper, director of the Faunhofer Institute for Manufacturing Engineering and Automation in Stuttgart, Germany, says much of the virtual factory concept is still wishful thinking, despite technological advances. Many factory processes still can't be simulated, he said, although he's convinced that by 2010 all the elements and processes of a factory could be represented in computer models.

The key will be adding virtual reality technology to the simulation systems of today. Technology maker Siemens AG of Munich, Germany, for example, runs a virtual reality laboratory in Munich, where users can see a 3-D image of a factory projected onto a curved screen by three projectors. They can travel down virtual aisles or fly to the virtual factory roof to get a bird's-eye view of the entire layout.

Building a virtual model is a lot of work, said Heinz-Simon Keil, head of the Center for Visual Engineering, as the Siemens laboratory is called. "But it's all worthwhile if the virtual model can be used over and over."

Virtual factories can be planned together by people in different locations with the help of software that allows for fly-throughs, Keil said.

And mere humans shouldn't worry. Although factories are now being designed digitally and are often staffed by more than a few robots, there will always be a need for employees to perform tasks that can't be assigned to machines. And, of course, someone will always have to program the robots or risk a science fiction nightmare. But that's another story.