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# A Tale of Two CAD SystemsPUBLIC ACCESS

Does Having Dual Computer-Aided Design Programs Give a Company Twice the Usual Benefits of Automation or Does it Mean Twice as Much Work for Engineering Managers?

[+] Author Notes

Michael Henry is compllter-aided-design manager of Waiter Lorenz Surgical Inc., in Jacksonville, Fla.

Mechanical Engineering 120(09), 70-72 (Sep 01, 1998) (3 pages) doi:10.1115/1.1998-Sep-3

## Abstract

Walter Lorenz Surgical Inc., Jacksonville, FL, specializes in the medical devices known as rigid fixation implants. Lorenz Surgical was purchased by Biomet Inc. of Warsaw, Indiana in the year 1992, which resulted in Lorenzo owning two computer-aided design (CAD) systems. In 1996, with the completion of Lorenz Surgical's new manufacturing facility in Jacksonville, all Lorenz operations were transferred back to Florida, including all the manufacturing equipment and its three seats of Unigraphics, which by then were running on Windows NT workstations. The company's management feels it could have stayed with Unigraphics and accomplished its goals, but that adding Solid Edge was a good move. It gave Lorenz flexibility in hiring, allowed it to buy more CAD seats than it could have if it had stayed with Unigraphics alone, and provided a very productive tool. Lorenz's surgical instruments are currently designed exclusively in Solid Edge. Instruments can be modeled in either CAD system, but the job goes faster in Solid Edge. The creators of Solid Edge put a lot of effort into usability, and this shows in how few mouse clicks are needed for common operations. Products that have many standard features, such as a screwdriver consisting of m any cylinders, are very quickly modeled in Solid Edge.

## Article

Many software vendors would certainly like to see their customers standardize on a single program, as long as it is theirs. And, all other things being equal, it is generally more convenient for users to maintain all their files on one system. But often there are considerations that make it necessary to use more than one competing brand of software in the same enterprise.

Lorenz Surgical engineers rely on parametric modeling to ensure that variations of existing implants and tools can be produced in the future.

This is particularly true of computer-aided-design (CAD) programs. Where 20 years ago a company’s engineers often would be responsible for designing most of the components that went into their company’s products, nowadays it is common to farm out both design and manufacture of many parts to independent suppliers, who may well use a completely different CAD system. Or a firm may decide to switch to a new software vendor for one reason or another, leaving engineers with a substantial legacy of engineering information that is impractical to transfer to the new system.

An instructive case in point is Walter Lorenz Surgical Inc., in Jacksonville, Fla. The firm specializes in the medical devices known as rigid fixation implants, which surgeons attach to bones to stabilize them while they heal. Lorenz Surgical’s particular field is implants for the bones of the face and head. Its products are used in cases of trauma—to stabilize a jawbone while it heals after a car accident, for example— and in reconstructive surgery, to correct problems caused by congenital defects and disease.

Lorenz Surgical was purchased by Biomet Inc. of Warsaw, Inc., in 1992, whereupon it quadrupled the size of its Jacksonville headquarters. It brought manufacturing in-house, into a new 80,000-square-foot production facility filled with state-of-the-art equipment. At this point, it received ISO 9001 certification, and hired many additional employees to keep up with its growth.

This recent history is the reason Lorenz has two CAD systems. Before the acquisition, Lorenz Surgical did not use CAD. Biomet, which also makes medical devices, was founded by engineers, and is a long-time user of a high-end CAD system, Unigraphics, from Unigraphics Solutions in Maryland Heights, Mo. After introducing its new subsidiary to Unigraphics, Biomet helped Lorenz manufacture its own products using the Unigraphics data to program computer-numerical- control machine tools.

Initially, Biomet kept a close eye on computer-aided design and manufacturing operations by installing everything in its facility in Indiana, and Lorenz started manufacturing its products there in 1993. In 1996, with the completion of Lorenz Surgical’s new manufacturing facility in Jacksonville, all Lorenz operations were transferred back to Florida, including all the manufacturing equipment and its three seats of Unigraphics, which by then were running on Windows NT workstations.

Soon after the move back to Florida, management at Lorenz started thinking about a second CAD system. The firm was adding personnel rapidly at the time, and could find few trained Unigraphics operators in the area. Florida has many civil engineers, but it doesn't have a strong manufacturing base, so there are few people with experience in mechanical CAD.

Implants and surgical instruments consisting of many standard features, such as this screwdriver composed of numerous cylinders, can be modeled quickly with Solid Edge, which requires relatively few mouse clicks to perform common operations.

The company was committed to Unigraphics because by then all of its existing implants had been modeled in that system. Unlike some companies that rarely reuse CAD data, Lorenz creates many new products based on ones already on the market. For example, it is conm10n to take an implant designed for adults and make it smaller for pediatric use. Also, as these products are sold internationally, surgeons in other countries often request adjustments for the different-sized facial features of people of different races. These kinds of changes are made by simply changing the parameters of existing models, using the Unigraphics parametric-modeling capability.

Although the firm wanted more Unigraphics operators, it was felt that it was too costly to hire trained people from out of state and move them to Florida. Another option might have been hiring people with experience in other CAD systems and training them in Unigraphics. However, the company was growing too quickly to take on the task of training itself, and didn’t want the expense of having someone else do it.

That’s when Lorenz started looking at a second CAD system. It did not plan to replace its Unigraphics systems since it wanted them for designing implants, but the company also makes the surgical instruments used to install implants. Engineers there had never designed these in CAD, but they planned to start. Since there were no legacy data to worry about, instrument design would be a good role for a new CAD system.

There were two main criteria for the new system. The first was that people be productive on it almost immediately. The second was cost: if Lorenz could find one that met its needs yet cost less than Unigraphics, it could get more seats. This led the company to consider midrange systems—in particular, Windows NT—based solid modelers that sell in the $5,000 range. A demonstration of Solid Edge (before its developer, Intergraph Software Solutions, merged with Unigraphics Solutions) had impressed Lorenz management. The system seemed to have a great deal of functionality for$5,995, and it looked easy to use. Word that Solid Edge was going to be acquired by Unigraphics helped convince Lorenz to buy it. Not only did the firm have good experience with Unigraphics Solutions as its CAD vendor, but it also anticipated a time when Unigraphics would integrate the two programs. (More about that later.) Lorenz purchased two seats of Solid Edge initially, although the number has since grown to six seats.

The first person hired to run Solid Edge was basically given the computer and the software, and left on his own. True to its reputation, Solid Edge turned out to be easy to learn. The CAD operator was highly productive with the software within 90 days. Part of this is because Solid Edge uses icons rather than multiple layers of menus, and part is due to its Smart Step toolbar, which basically walks the operator through the modeling process.

Today, all of Lorenz’s CAD operators and design engineers are CAD-literate, and if two of them are given the same part to create, one with Unigraphics and one with Solid Edge, it will take about the same amount of time in most cases. However, only one CAD operator is proficient in both Unigraphics and Solid Edge. This is not something I would recommend. If a company is going to have two CAD systems, it makes sense to cross-train as many people as possible, so that there will always be someone available for jobs like engineering change orders, regardless of the system a part was designed in.

## Assigning Work

Since the designers and CAD operators are not yet crosstrained, jobs are assigned based on the type of part being modeled and the relative strengths of the two CAD systems. At this time, new implants that are variations of existing products are designed in Unigraphics, as mentioned earlier. Completely new implants are designed in either Unigraphics or Solid Edge. Typically, these begin as a collaboration between Lorenz engineers and a surgeon. Sketches from their discussions are often scanned, imported into the CAD system, and used as the basis for the implant’s two-dimensional profile. The actual part is basically an extrusion of the 2-D profile. All that is really needed from a CAD system in this situation is parametric modeling (for the ease of creating related products in the future) and the ability to produce machinable geometry. Both Unigraphics and Solid Edge offer these capabilities, so the choice of system is usually determined by which design engineer is available and what system he knows.

The benefits of having two CAD systems outweigh the drawbacks.

There is one type of implant, however, that is always modeled in Unigraphics. This is a custom implant created from CAT-scan data of a patient. In this situation, the CAT-scan data are imported into the CAD system, and the implant is designed around the resulting geometry for a perfect fit. The process of converting CAT-scan data to CAD data format was worked out in Unigraphics, so that is the system used for these projects. Unigraphics is also used exclusively for screws at this time. Screws are used to fix the implants to the patient’s bone. Screws can be modeled in Solid Edge, but it goes much faster in Unigraphics. This program’s law curve function is a very efficient tool for modeling screw threads. It creates a path that a helix follows, so a designer simply attaches a sketch of the thread form to the helix of the screw, and the program “cuts” the helical pattern from the solid mass of the screw.

Lorenz’s surgical instruments are currently designed exclusively in Solid Edge. The main criterion these instruments must meet is to feel good in a surgeon’s hand, so some have irregular shapes. Instruments can be modeled in either CAD system, but the job goes faster in Solid Edge. The creators of Solid Edge put a lot of effort into usability, and this shows in how few mouse clicks are needed for common operations. Products that have many standard features, such as a screwdriver consisting of many cylinders, are very quickly modeled in Solid Edge.

That is not to say that engineers never have any questions about how to use Solid Edge. They do sometimes call for technical support, and the support people seem to be knowledgeable about both products. For instance, if there is a question about something being done in Solid Edge and a designer mentions that the company also has Unigraphics, the support person might reply that Unigraphics is the preferred tool in that situation, and explain how to solve the problem using that software.

## Plus and Minus

For Lorenz Surgical, Unigraphics was and continues to be a CAD system that addresses its design and manufacturing needs well. The company’s management feels it could have stayed with Unigraphics and accomplished its goals, but that adding Solid Edge was a good move. It gave Lorenz flexibility in hiring, allowed it to buy more CAD seats than it could have if it had stayed with Unigraphics alone, and provided a very productive tool.

There are drawbacks to having two CAD systems. Some are trivial, such as the fact that the two programs control the plotter differently. One uses hardware controls and one uses software controls. Before a design engineer sends a drawing to the plotter, it is necessary to get up and make sure the plotter is on the proper setting. Plans are to solve this problem by buying an additional plotter.

A second drawback is the fact that, until Solid Edge version 5 became available, the two CAD programs were based on different geometry kernels. Unigraphics uses Parasolid; Solid Edge used ACIS. (Lorenz knew this when it acquired Solid Edge, of course.) Having different geometry kernels basically prevents data from moving between the two systems. It could be done using ICES, but this would lose the intelligence contained in the models.

Custom implants and related parts are designed around 3-D images of a patient's CAT-scan data to provide a perfect fit.

Solid Edge 5, which is based on Parasolid, now allows easier transfer of data between systems, but it is not until version 6 that all the intelligence will be included in the transfer. That release will allow engineers to design parts in one system and incorporate them into assemblies created with the other, providing flexibility in assigning projects.

Would I recommend this arrangement—a high-end and a midrange CAD system—to other companies, based on the Lorenz experience? The parent company, Biomet, is considering a similar move and asked me for my recommendation. For Lorenz Surgical, the benefits of having two systems outweigh the drawbacks. This was the case even before the two programs shared the same modeling kernel. As the integration between them improves, and more Lorenz design engineers are crosstrained, the drawbacks will disappear and we may have the best of both CAD worlds.

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