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Replicating a Rex

Satellite Models used 3-D scanned images to make 33 replica bones for Sue, the $8.36 million T-Rex.

By Karen Koenig

A little plastic “surgery” can work wonders for anyone — even a 67 million-year-o
The largest, most complete Tyrannosaurus rex ever found, Sue is 42 feet long and, according to Chicago’s Field Museum, possibly weighed 14,000 pounds when alive.
ld fossil like Sue.

Kelly Hand, owner of Belmont, CA-based Satellite Models, used plastic to replicate 33 missing bones for Sue, Chicago’s Field Museum’s famous $8.36 million Tyrannosaurus rex. Using a combination of laser scanned images and CNC machining, Hand’s company manufactured an arm bone, the right foot and nine ribs from RenShape 350 modeling board.

“The original fossils, or in some cases a casting, was laser scanned by Scansite in San Rafael, CA,” Hand says. “After capturing the original data, we then moved it around, spun it in ‘space’ and visualized it from every angle to create a mirror image. You have to make sure that it’s to scale, that the size and everything is correct.

“We then took the scanned data and brought it into our CAD system for rapid prototyping. We moved (the image) into the correct position that worked best for our machining process,” Hand explains.

 

He then met with people from the Field Museum
To replicate 33 missing bones, original fossils, or in some cases castings, were laser scanned by Scansite and a digital image was made (top right). A mirror image of the bone was then created to scale. File data was then transferred to Satellite Models and owner Kelly Hand created the toolpaths.
“to learn what their requirements were, what level of detail was needed. They wanted the bones to be similar, but not to be mistaken for the real bones.”

The next step in the process, Hand said, was to develop the toolpath for the machining process on a Quintax five-axis CNC router. He estimates that it took three to six toolpath programs to create each replica bone.
“Once we selected the carbide tooling, we began to rough out the shape. You have to do this slowly, taking away the excess material until you get to the final surface of the bone you’re creating,” Hand says.

“For the process, we started with big cutters. We used smaller cutters for the finish passes, making passes in incremental steps.” Depending on the level of detail, the finish passes took from eight to 24 hours to complete, he adds.

Only one side of the bone could be machined at a time. “We had to create a fixture, register it to the machine, flip the bone over, reposition it, then repeat the process. This enabled us to get the undercuts and all the other details we couldn’t get before,” he adds.

It took Satellite Models approximately three weeks to complete the project. Although this is not the first dinosaur the company has worked on — a previous project involved replicating bones for a triceratops in the Smithsonian Institute — Hand says he enjoys the challenge of working with museum artifacts.

Projects, he says, that he can sink his teeth into.

For more information on Satellite Models, go to www.satellitemodels.com

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