Solid Modeling Offers Benefits for Design of Truck Bodies, Trailers

AFTER eight years using a two-dimensional CAD system, the W. F. Mickey Body Company, Inc in High Point, North Carolina, has found that a switch to three-dimensional modeling has improved communication with suppliers, shortened product cycles, and has lowered development costs-particularly in the area of tooling.

Mickey, a manufacturer of aluminum truck bodies and trailers, purchased the system for less than $6,000 per seat in software costs.

"Our business is based on aluminum extrusions," explains John Hargett, manger of research and design. "It's a 2D activity that requires a 3D approach, but even so, we weren't going to abandon our old 2D system and all that legacy data for something that was hard-to-use and expensive."

Mickey selected a Windows-based program, Solid Edge from Intergraph Corp, Huntsville, Alabama.

Building Better Bodies The W. F. Mickey Body Co., which employs 300 people, has a three-part product line: beverage trucks and trailers, van bodies, and ambulance bodies.

When a customer orders a Mickey body, he specifies such features as the bay width, floor pitch, overall height, length, shelf and door location, and any other requirements specific to his product line and delivery technique. With the old 2D system, information was supplied to vendors and manufacturing in the form of section views and layout details. For a complex part or assembly, the required section views and assembly detail could take up to five days to complete. In addition, the two-dimensional software did not give any part interaction (fit) information and did not support assembly modeling.

When company officials began considering a solid modeler, one of the first decisions they made was to stick with PCs as the CAD hardware platform.

"We're a family-owned company and we do things like most families-we hand things down," says Hargett. "Engineering gets the hottest PCs available. When we upgrade, we hand our computers down to another department. They roll theirs down to another department, and so on. The problem with going with RISC workstations is that we would have been locked into a platform with a high upgrade expense that we couldn't pass down.

"We have eight people in our engineering department. With some of the other programs, we would have needed about $20,000 per seat of software to have uniform capabilities throughout the department. To bring the price down, some vendors would suggest that we buy only a few seats of 3D and a few of drafting. But our drafters do a lot more than drafting. That approach would have created a bottleneck by requiring them to stop and pass a design back to an engineer with the right software. Solid Edge let us put exactly the same software on everyone's desk."

Solid Benefits One of the first benefits of solid modeling that designers noticed was the ability to evaluate assembly integrity. The various parts of truck bodies are all eventually joined during assembly. But until the move to solid modeling, designers had to work with multiple 2D views without the ability to see how all the pieces fit together. By creating an assembly and having an image of it on the screen, fit problems are detected before they reach production assembly.

Designers are finding ways other to improve products that were not evident before. "Being able to see all of the parts instead of multiple 2D snapshots enables us to see possible modifications to one part of an assembly that might totally eliminate the need for another part," says Hargett. "These things weren't nearly as obvious when we worked with 2D drawings."

Another benefit of solid models is that they can form the basis for finite-element analysis (FEA). This is particularly helpful in W F Mickey's efforts to expand into Europe. Regulatory agencies there require FEA results as part of the certification process. In the past, an outside analysis contractor had to create finite-element models from 2D drawings. By importing Solid Edge models, he can deliver results weeks sooner.

Fast Cast A recent project involving a fairly complex casting for a beverage body offers a good example of how solid modeling has improved communications with suppliers. The part, which is now being patented, was modeled in Solid Edge and while the design was in progress, a representative from the casting company came in to discuss the part. By manipulating the model on the screen, designers were able to give him a much clearer understanding of the part and its structural requirement-compared to the old approach of showing 2D views in a layout format.

During the meeting, the caster was able to suggest possible changes that would reduce casting costs. "While he was sitting there, we made modifications that made the part both easier and less expensive to produce," says Hargett.

To give the casting vendor an even better understanding of the part, the Solid Edge model was saved in .stl format and sent electronically to a stereolithography service in California. In less than a week, Mickey designers had a physical model that the casting house used to make one-off parts for testing. This resulted in significant savings compared to the previous approach that required a commitment of several thousand dollars in tooling for test parts and weeks for the 'temporary' tooling to be produced.

When the casting design was finalized and part ready for final tooling, 12 section views were created for each of the four variations of the part from the solid model. This took only a few hours, compared to at least three weeks that would have been needed previously.

"In Solid Edge, you pick the part you want to section, draw the section line, pick which side of the line you want depicted and Solid Edge produces the section automatically," says Hargett. "This may not seem important to engineering departments with a full complement of detailers to perform this function. But our product is not engineering. It is a quality body delivered on time to a satisfied customer. Whenever we can find an advantage to expedite the engineering process through computer-generated detail, it enables the engineer to concentrate on engineering rather than explaining 'concept' to a draftsman and spending endless hours of checking to ensure that an interpretation does not violate the intent of the design."

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