(Adapted from original story in 3dprint.com)
Triebold Paleontology, Inc. (TPI) mounts and restores fossil skeletons and provides casts of them to museums around the world.
Its headquarters are home to a collection of casts and original specimens which are on exhibit at the company’s hands-on natural history museum, the Rocky Mountain Dinosaur Resource Center.
TPI were looking to add a Stegosaurus to their collection – particularly the Stegosaurus at the Denver Museum of Nature and Science. Traditional casting wouldn’t work in this case, as the Stegosaurus is more than 26 feet long and over nine feet tall. This would still make for a do-able cast if the specimen could be taken apart, but that wasn’t possible.
The dinosaur was mounted as a permanent installation in the 1990s, with steel shaped around it, welded in place, and permanently puttied to the bones, making it impossible to ever take apart. Thus, 3D scanning entered the equation.
“We needed to three-dimensionally digitize the skeleton that could not be dismantled so that a replica could be 3D printed,” said Matt Christopher of TPI. “The dimensions and surface details needed to be close enough to what we would get from a silicone mould so that we could hand-finish 3D prints to look exactly like the original specimen.”
To scan the dinosaur, used a structured light 3D scanner to 3D scan individual bones and regions of the skeleton as individual projects. In the end, they had 629 individual scans across 71 scan projects. To save time, they decided to skip scanning parts that could be mirror-imaged to generate the other side, like the legs and ribs.
“We were able to capture all of the elements we needed, from the tip of the nose to the huge spikes at the end of the tail,” said Christopher.
3D printing the bones was a big job that was taken on by multiple 3D printers and took six months. When the prints were finished they were lightly resurfaced by hand and prepared for moulding by adding mock-ups for internal steel armature and articulating some specimens to be moulded in sections rather than as individual bones. Each completed bone or assembly were then moulded in silicone rubber. The moulds were then fitted with internal steel to be surrounded by plastic resins in the casting process.
The plastic was poured around the steel, so no external armature that would hide bone surfaces was needed. With the casts poured around the armature, the skeleton can be assembled in any one of an infinite number of poses and the steel protruding from inside each plastic cast welded together as required. The mounted skeleton was then ready for hand-painting and delivery.
“We were able to marry the best technologies of today with the most advanced traditional methods of moulding and casting to create an exact copy of that great dinosaur without even touching it,” added Christopher.
(See the full 3dprint.com story)