Issue: Volume: 23 Issue: 8 (August 2000)

A Blast from the Past

Using digital technology to retrofit classic model kits

By Karen Moltenbrey

During the height of their popularity in the 1960s, The Testor Corp.'s (Rockford, IL) Weird-Oh line of monster-like drivers in dragster-style model cars were, well, weird. Last fall, sporting drivers with newly styled heads that gave them an even "weirder" look, these car-crazed denizens of the fictitious town of Weirdsville became the stars and namesakes of a new animated television series, prompting Testor to reintroduce its model kits.

Prior to creating the 3D Weird-Oh models for the animated television show, Mainframe Entertainment, a Vancouver, Canada, animation facility, refashioned the characters' dated appearance to appeal to its young crop of millennium viewers. While Testor wanted to cash in on the Weird-Ohs' newfound popularity, it couldn't risk spending tens of thousands of dollars to make new die molds for reproducing a small number of its Weird-Oh model kits.
Using CAD technology, Testor redesigned its nostalgic Weird-Ohs line of model kits. Above is the original model of the character Davey. At right is his revamped look for the new Weird-Ohs TV show, and lower left is the newly engineered model sporting a re

At issue for Testor was how to update its expensive manufacturing molds from the '60s to encompass the few, albeit noticeable, new character updates. "Testor wanted me to redesign the Weird-Ohs' heads in the quickest, easiest, and least expensive way possible," says Ken Stark, mechanical designer for the hobby company. His solution to this situation was to use digital design and reverse engineering.

"A plastic kit like this retails for about $10, so you have to stop and think about how many kits we would have to sell to make a profit after creating a new $70,000 tool," notes Stark. "That's why we wanted to revamp our old technology."

The Weird-Ohs were (and still are) a strange-looking bunch whose lives evolved around their "need for speed"-so much so, in fact, that they were literally attached to their roadsters. Unlike most other model kits for airplanes and cars that contain a hundred or more pieces, the Weird-Oh models are fairly basic, with only 15 to 20 pieces (the real attraction is painting them). For Stark, this meant that only a small portion-two cavities in most instances-of the injection mold for each kit's "family" of parts needed reworking to accommodate the new pieces.

In concept, blending the old and new technologies seemed fairly simple; implementation, though, proved difficult. Stark's first challenge was to create digital versions of the original models, which were produced years ago by skilled craftsmen who carved the models by hand. Because Testor intended to reuse the original injection molds for most of the pieces to each character kit, the digital data had to match the models exactly or the pieces would not fit together properly. To achieve an exact digital replica, HighRes Corp. (La Jolla, CA) reverse engineered the physical model through digital scanning. "Within three to four days, HighRes gave me spline definitions, from which I could create surface definitions for the bodies," says Stark.

For the redesigned heads, Stark acquired Mainframe Entertainment's animation models, which were created for the TV show using Softimage's (Montreal) software program. Because of all the undercuts (hollow spaces that cannot be molded) that are created during modeling to make the images more compelling-but not manufacturer-ready-the Softimage models had to be reworked. "For animation, you just do whatever is visually correct, as opposed to in the mechanical realm, where things need to be more precise. It's like using Play-Doh vs. an Erector Set," Stark explains.
Image courtesy Testor.

But translating between CAD/CAM and animation programs is difficult. "It exists, but it's not really there yet," Stark contends. After spending a great deal of time searching for an effective translation package, the designer chose Okino Computer Graphics' (Toronto) PolyTrans NURBS translation software, which he used to convert the Softimage information into a surface-based IGES file. From there, he ported the surface data into his computer-aided design package from CADKey (Marlborough, MA) running on a Pentium-based PC.

Using CADKey's FastSurf surfacing package, Stark then manipulated the node points of the surfaces and removed the undercuts "to make the data 'manufacturable," he says. While this slightly altered the look of the characters-for instance, the ears of the model characters are blended in against their heads instead of protruding outward, as they do in the animation models-those differences were negligible.

With both portions of the data puzzle complete, the next step was grafting them together. "Using CADKey, I basically chopped the old models off at the neck, put the new head on top of the torso, and blended the computer representation together in the neck area," explains Stark. To ensure that the heads were placed and blended correctly, then positioned to reflect the "attitude" of each character, Stark deferred to the experience of the Mainframe animators by sending them assembled original models to use for guidance. "Davey is the coolest kid in town, and when he rides his motorcycle, his arms are stretched out and his head is cocked a certain way," he adds. "And we wanted to project that look."

The most difficult task, says Stark, was preparing the newly blended model for manufacturing, as each model would have to be split into two mirrored halves so the mold could be opened and closed. "I spent about a week tweaking the new model to accommodate our needs," he says. After Stark created an injection moldable part that could be split down the middle, he forwarded the CAD file to 3D Systems (Valencia, CA), which created a stereolithography prototype. A tooling shop then used the prototype to create new head inserts for the molds.

"By creating new cavities for the heads, we now have the option to pop them out and replace them with the old ones to create model kits with the original heads," says Stark. "This was far less expensive than creating a whole new mold, and it provided us with the flexibility to interchange the heads, if we decide we want to do that in the future."
Redesigning just the heads of the models saved a tremendous amount of money, since the manufacturer could reuse its expensive legacy die molds. Above is the original Mama character. Above right is the 3D animated TV version, and at lower right is the new

This process also proved useful in post-manufacturing. Stark requested two sets of models during rapid prototyping-one for tooling and another that was painted and displayed at a hobby trade show so the company could collect feedback on the product it was about to remarket.

If these new plastic kits, which were released a few months ago, are well received, Testor may reintroduce the other original Weird-Oh characters by using the same technique. "What made this project so different," Stark says, "was taking a tool that was made the old-fashioned way back in the '60s and re-engineering it using technology from the computer age."

CADKey, CADKey Corp. (