This was not a short project working with the entire skeleton, but individually, it did not take long to bring each bone into 3D space using photographs and Autodesk 123D Catch. Once the photos are uploaded and stitched, 3D models were exported which I cleaned up and closed with Blender, but just about any 3D design program will do. From there I exported finished models for slicing and printing.
Step 1: Photos and stitching
The first step was propping the bones up in modeling clay. Where possible, many bones are articulated and tacked with glue to save time. I found that scratching marks into the clay base with my fingernails helped provide more points of reference when manually stitching images together. I also found that focus and lighting are important considerations.
I chose to shoot images outside after having no luck with the lighting conditions in my house. I shot as dusk approached or when I had sufficient cloud cover to produce well dispersed low-angle light. I found that the sky and relatively featureless backgrounds do not work well. It is important to have variety in the background throughout the images to provide queues for the stitching process. I used the macro feature on my point-n-shoot camera and attempted to carefully shoot at perspectives about 15 degrees apart. Each specimen was captured with between 45 and 65 images which were uploaded to Autodesk 123D Catch. From here I deleted background objects which were preserved around the subject as meshes and exported .obj files for further editing.
Step 2: Cleaning and closing
I used Blender to import the .obj files, clean and close them, and export .stl files. The slicing software I used also works with .obj's, but using two different model types helps me keep track of which files are ready to slice and which may not be.
Step 3: Fitting the Print Bed
Working with Ultimaker 3D printers, my available print bed dimensions are 200x205x205mm. Some specimens exceed these dimensions so these must be split into two models.
Step 4: Slicing and Printing
I'm using Cura for slicing. For the sacrum and illia (hip bones and fused vertebrae between the hips) I was still able to combine both parts and print them with a single toolpath. When these parts were finished and support materials removed, I used the same super glue I use on real fossil dinosaur bones to glue the two halves of the model together at the (nearly) flush surface they were divided at.
Step 5: One Psittacosaurus, hot off the press, er, printer!
Here you can see the very colorful skeleton laid out in articulation. Only half of the skull is shown here as the other half was still being printed when this photo was taken. All parts were printed from PLA, albeit many, many shades. I was not prioritizing aesthetics all that much. I mostly wanted a model to work with for preparing an armiture to mount the real skeleton.