In preparation for a new paleontology exhibit focused around Pleistocene fauna, one of the specimens to be included is a partial skeleton for Bootherium, a relative of the musk ox.
While VMNH does have Bootherium skeletal elements in its collection, there were not enough to reconstruct a full skeleton. Therefore, we utilized 3D scan files from the University of Idaho and had the skeleton printed by Virginia Commonwealth University and Mercer College.
There are several benefits to 3D printing over molding and casting including that there are no molds to store and the printed elements are lighter in weight. However, there are negative aspects about 3D printing. The printer that was used to print Bootherium has a relatively good resolution so many of the finer details of the bones was preserved in the print; however, there are artifacts (undesirable features) that can occur during the printing process. One artifact that cannot be avoided are the print lines that form as the printer head lays down the various layers of plastic. For the exhibit, these plastic ridges have to be sanded until smooth so that it more closely resembles the texture of the original bone.
For those out there more familiar with 3D printing, you might be wondering why we are sanding instead of using acetone to melt the plastic until it is smooth. Thats because PLA plastic was used instead of ABS plastic (which melts when in contact with acetone). The reason for this choice was due to the fact we had to combine multiple pieces together so we wanted a plastic that would provide negligible shrinkage. PLA plastic has the least amount of shrinkage when compared to ABS. Solvents for PLA are fewer than for ABS and more flammable and toxic than acetone. We value our health so we chose the lesser evil of sanding the ridges away.
Larger skeletal elements, such as the skull and long limb bones, had to be printed in multiple pieces and then assembled upon arrival at VMNH. The pieces are glued together with acrylic cement and any remaining gaps filled in with apoxy putty. Once we finish sanding the various elements, Bootherium will be assembled, painted and ready for display. Wish us luck! And many thanks to all the volunteers who have helped us thus far in preparing this skeleton!