First Test Prints and Metashape Experience.

 

    This week focused on printing three test prints of artifacts as well as learning how to use Metashape on a normal household object to prepare for the actual five artifacts from the Sanford Museum. This blog will focus on the printing process as well my introduction and progress with Metashape.

                The printing process for 3D artifacts involves taking .STL or .OBJ files prepared in Metashape and Blender, which I will also detail those two processes later in the internship, and loading them into a 3D Slicer. To prepare the three artifacts for printing I load them into a series of slicers because each slicer, while they do the same task, each is traditionally accepted in the 3D printing community as having a feature they perform very well while the other features fall short. Therefore, loading the files into a variety of different programs allows for a greater control over the process as well as creating an easier workflow.

                Prusa slicer is the first slicer that I load each model into and add support beams on the model itself to make the model actually printable. I then export the test prints with supports into Chitubox, load them onto the build plate digitally and complete any hollowing and draining if the models are large enough to warrant it. Finally I export these files again into the Photon slicer which makes the file actually printable as a .pws file for my printer.

Photo of wax seal print with support beams

Once the models are printed I wear protective equipment to avoid resin toxicity and scrape the models and their supports into a vat of acetone to clean off any liquid resin residue. After agitating them in the acetone for approximately 10-15 seconds I dry them and transfer them to warm water to make the resin more pliable. After they models become more flexible I take an excato knife to cleanly separate the supports off of the model. This step takes great care and precision or else the printed replica will have moderate to severe support marring. Finally, once the models are free from their supports and they air dry, they are then placed under a UV light for five minutes to cure fully which not only hardens the model but makes it fully safe for handling.

Wax seal resin print top, and arrow head resin print bottom.

While the test prints and the printing process went by flawlessly this week, the process for learning and using Metashape did not. I watched a lot of tutorials on Metashape and used a test model to perform the operations. To begin I took photos from all around the model with approximately 75% overlap between each photo. Once I assembled the profile of images and loaded them into Metashape I aligned the photos forming the pictures below.

Image of the sparse point cloud

The image above shows a sparse point cloud of the model which, instead of loading all points, only loads certain points to give a quick idea of the shape of all scanned assets which makes the model easier to work with and delete unnecessary data. Once just the model was in frame I built the dense point cloud which made it evident that the operation was a failure as only the front half was rendered correctly while the back half was not. This means that the program was not tricked into thinking I moved around the model because the texture on the turn table gave it away. The next step forward is to take additional steps such as hiding the texture on the turn table and starting a process called masking which is supposed help with this turn table issue.

Image of the more resource intensive dense point cloud.