The University of West Florida’s Archaeology Institute houses one three-dimensional (3D) scanner and two 3D printers for individuals in the Anthropology Department to scan, print, and share artifacts. This fall, we decided to print and magnetize three refitting Civil War case shot fragments from the Natural Bridge Battlefield Historic State Park and share our work at the Society for Historical Archaeology Conference in January 2017. The goal of this project was to create a tool so that visitors to the park can have a hands-on experience with the object.
The digital model of the case shot created by Tristan Harrenstein using photogrammetry.
So far, we have attempted to create a magnetized plastic model of the shell in two ways. For the first attempt, we placed magnets inside the model as it was printing. To do this, we used Simplify3D, the software associated with the Fusion3 F306 to create enough space within the model to fit the magnets. This was done by decreasing the infill percentage, a setting that controls how hollow or dense the model will be. We lowered the infill percentage to about 2%, just large enough for the magnets to fit within the model. We hot glued 12x13mm round ceramic magnets in the gaps within the plastic modeland waited for the plastic to slowly build around it. Using this method, someone has to “babysit” the printer and wait for the right time to insert the magnets.
This process took almost twelve hours, with the three of us (graduate student Katy Patterson helped) rotating responsibility every few hours. We were able to successfully implant the magnets and have other magnets stick to the edges, but the structural component of the model was very weak. When we tried to use the same method on a second fragment, many of the magnets were not strong enough to attract through the plastic, and because of the way the plastic model was situated on the printer, it turned out to be so structurally unsound that the model broke.
For the second attempt at magnetizing the case shot, we used the complete plastic models and drilled holes in them and placed smaller magnets inside. This method was more successful, although it is still a rough prototype. We increased the infill percentage to its normal rate and printed the three fragments using the Fusion306 printer. After the three fragments were printed, we took a Dremel and drilled into the edges of each model, making about 2-3 holes per edge.
Once again, we inserted magnets but this time we used smaller, stronger neodymium Rare Earth Magnets from Harbor Freight Tools. We placed them in the holes and secured them with super glue. Our second draft of the model worked! Although it was a very rough version, the three fragments stuck together and it can still be a great tool for teaching students, visitors, or researchers about the artifact.
Our third draft will be an edited version of our first. We plan on inserting the smaller and stronger magnets into the plastic model as it prints. This will allow for the infill percentage to be high enough that the structural integrity of the model will not be compromised and for the magnets to be attracted through the plastic.
Tristan Harrenstein has also suggested an alternative method would be to create a space for the magnet in editing software like Blender and insert the magnet after printing. Creating plugs to fill the remainder of the space created would allow for a more visually coherent model than the drilled method, while being less time consuming than the embedded method.
We look forward to seeing the outcome of these two methods and stay tuned to find out how it went!
About the Authors
Mariana Zechini is a graduate student at the University of West Florida. She received her B.S. in Anthropology at Virginia Commonwealth University in 2014 and has four years of experience in 3D scanning archaeological materials. Her thesis focuses on analyzing stable isotopes from human remains from a medieval cemetery site in Berlin, Germany.
Janene Johnston is a graduate student at the University of West Florida. She received her B.A. in Anthropology at Eastern Kentucky University in 2011 and has worked as an outreach assistant with the Florida Public Archaeology Network for three years. Her thesis focuses on surveying and analyzing the Natural Bridge Battlefield, a Civil War site near Tallahassee, Florida.