February 14, 2013

Osteological 3D Scanning/Printing Update

For the past month or so, UWF grad student Colin Bean and I have been tooling around with my MakerBot Replicator 2.0.  I'm most interested in printing bones -- namely, pathological ones that we don't have in our osteology collection here -- so Colin's done some 3D modelling of bone and I've printed a variety of test cases.

When we were getting started, we were mostly printing other people's models.  So we have the MakerBot printing a whole hand (about 75% complete in this picture):

Hand bones (file)
The problem with printing multiple bones at once, though, is that the filament doesn't completely stop extruding.  This results in a hairy mess.  I'm not particularly interested in shaving my phalanges.  So I did manage to print some individual bones, and they turned out pretty well, without any supports or a raft:

1st metacarpal and distal phalanx

I got excited at that point and wanted to print something larger.  The main problem with bones, though, is that they're not flat.  This means it's hard to print them without supports (extra bits of plastic).  I found this file for a full-size scapula without supports; to print it requires the scapula to be in two pieces, sectioned along a flat plane.  This worked out pretty well, although no amount of sanding could blur the glue joint.  Still, in a few hours' time, I had a complete, full-scale scapula.

Scapula in progress (file)
Finally convinced we could print bone, we got ambitious: Colin 3D scanned this animal vertebra I found in the woods, created a 3D model, and we printed it.  Wonky support plastic aside, it came out much better than we'd expected (to be quite honest):


Circling back to my main goal in getting the MakerBot, I want some copies of pathological bone.  We don't have much beyond the normal pathologies in our teaching collection: osteoarthritis, healed fractures, periostitis.  While we are planning to scan and print some of these, I also downloaded 3D models from the University of Bradford's Digitised Diseases project.  You can download the full 3D model (including texture, which doesn't print but is neat), and the .obj files can simply be loaded into MakerWare (MakerBot's printing software) and printed.

This morning, I printed a model of ankylosis of proximal and intermediate hand phalanges.  Here are side-by-side pictures of the model and my print:








It was printing pretty well until the filament spool got snagged (which happens altogether too often), and I didn't notice for 10 minutes.  So I had to stop the print job at 85% complete, as there's no way to make the printer go back a bit and re-do what it missed.  (The printed bone is sitting on the flat, incomplete side.)  One thing that was a bit problematic: figuring out the right dimensions at which to print the pathological bone (which, of course, doesn't share the same dimensions as a normal bone).

So we're getting pretty good prints, but the support structure is still an issue.  I am considering upgrading to the new MakerBot 2X because it has a dual-head extruder.  This means that, in addition to being able to print in two colors, it's possible to print two slightly different materials -- so the support structures could be made out of dissolvable filament, thereby no longer requiring me to shave random bits off the bones.  (Honestly, my fingers can't handle much more of the shaving.  I keep nicking myself with the scalpel because I'm clumsy and impatient.  Hence why I never wanted to be a doctor.)

More updates to come as we hack on this MakerBot some more.

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