By Karen Moltenbrey
Not long after adopting Parametric Technology Corp.'s (PTC; Waltham, MA) Pro/Engineer computer-aided design platform, engineers at the Track-Type Tractors Division of Caterpillar, a heavy-equip ment manufacturer in Pe oria, Illinois, embarked on an ambitious three-year program to convert all its existing 2D CAD drawings for its entire product line into 3D Pro/E models. The goal was to establish a comprehensive framework for future product redesigns that would meet impending federal emission regulations. Now, this time-consuming effort is beginning to pay off, as the engineers are in the middle of tackling an extensive redesign of the company's bulldozer tractor line in an effort to meet new regulatory requirements and satisfy consumer needs.
"Because the entire current-production tractor geometry had already been transferred into Pro/Engineer, we have been able to significantly reduce our design time for the next-generation models," says Steve Hyland, a technical manager at Caterpillar. "We are using our solid models as a baseline for the development work we are doing now."
Caterpillar's bulldozer product line, in existence for several decades, had un der gone a number of updates. Then a few years ago, PTC was notified of impending federal exhaust-emission standards that the six-model line would have to meet in the year 2001. "We knew these regulations were coming, and we knew our schedule would be extremely tight, since our entire line would be affected," says Kurt Rig gen bach, configuration engineer. "The only way we envisioned completing this redevelopment effort on time-and uncovering design alternatives that would give us a satisfactory product-was to use solid modeling through out the process."
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| The use of Pro/E solid models helped Caterpillar complete an extensive redesign of its bulldozer line in time to meet new federal regulations. |
In the past, when 2D tools were used, this type of redevelopment effort would have resulted in a far lengthier design process, Hyland says. "We would have taken our best shot, and a configuration engineer would have started putting down lines in the 2D world that would have led us down some design path, whether it was the correct one or not," he explains. "With solid modeling, the engineers looked at numerous alternatives that enabled us to meet the regulations without making significant concessions relating to the size and balance of the tractor and the ability to control its tools."
According to Riggenbach, the close coupling of the front blade to the tractor improves the machine's overall balance as well as blade penetration and prying capability-a design envelope that was optimized after years of engineering. Enlarging the bulldozers to incorporate the necessary components for regulatory compliance, however, would have resulted in poorly balanced and less-capable machines.
"If you look under the sheet metal, there's not a lot of air; almost all the space is occupied," Hyland notes. "There's a specific parameter we shoot for relative to balance. If you have to add more [components to meet the regulations], then you have to ex tend the length of the machine to give you more space, but then you have to widen the unit to maintain proper weight distribution. Eventually, it grows to a size beyond what the customer wants."
With spatial engineering a major issue in this project, especially for the engine area, the importance of using 3D solid modeling became even greater. When you look at our products, Hyland says, there are a lot of components-such as the power train as sem blies, hydraulic hoses, and electrical wiring-snaked throughout the machine, all of which compete for the same space. By using Pro/E's suite of tools, the group was able to try a variety of configurations without a lot of expensive and time-con sum ing physical mock-ups, as would have been required using 2D. "With 3D modeling," says Rig gen bach, "it's like we're working with the components themselves, but only on the tube."
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| Virtual prototyping enabled engineers to explore numerous redesign alternatives before building physical prototypes. The final solution allowed Caterpillar to fit all new emission-control components into the existing tractor body, whose size and shape had |
In addition to visibility studies, using solid models also provided the team members with the tools to perform structural and fluid-dynamics analyses. As a result, they were able to produce an optimal design much faster. "We can do far more iterations using 3D prior to actually building a [prototype]," Rig genbach notes.
While the objective of the redesign-to lower the emission levels-was clear, the road to achieving this was filled with bumps and turns. "It was the responsibility of the engineers to look at all the different ways of achieving that objective, and evaluate the pros and cons-such as price, performance, and features-of each option," Hyland says. Using Pro/E helped the group members achieve that goal faster and with a higher degree of reliability, he adds, because they were able to use the solid models to investigate the alternatives within the existing envelope of the vehicles.
After initial testing, the group decided on a redesign that did not change the width or length of the vehicles. "But we had to weigh that against the difficulty of stuffing the new components in to the package we al ready had," Rig gen bach notes. While both op tions presented unique challenges, the decision to stay as close to the original packaging as possible was eased with the availability of 3D CAD models.
Previously, when the team was faced with complex situations where various components were competing for the same space, it was forced to work out a design using physical models. "We would have had to build the tractor [mock-up] and then route the hoses, which would have delayed the [redesign] program," Riggenbach ex plains. "We can now do this electronically much earlier in the design phase, allowing us to check for interference before we order parts or build a physical model."
Hyland estimates that by using the Pro/E tool suite, the company cut its design cycle time (from concept to delivery) in half. He credits most of the time savings to using 3D design and analysis, which is enabling the team to hit the proving grounds with products that are more likely to succeed in fewer design cycles.
Key Tool Pro/Engineer, Parametric Technology Corp. (
www.ptc.com)