Tuesday, March 10, 2015

3D Printing Bones on my Printer!

I finally have my 3D printer working! It is a home-designed and built unit. The printing head moves in the X-Y plane at the top of the unit, and the build platform drops down as the build progresses. Many printers are like this. like the Ultimaker (r). Mine has a build volume of 8"x 8"x 17" (200mm x 200mm x 425mm for those of you who think rationally). This will let me print out and of Bernie's bones full size, including the whole skull.

Since this blog is about Bernie (and Bernice and Bernard and Beatrice and...) some of the first items I've been printing are copies of Bernie's bones. I've got a couple of brain cases, palate, etc. I'm considering a full skull, but the printer is not reliable enough to print the 60+ hours it will take to do a full skull. In fact right now after about 40 hours of printing the extruder barrel is broken. That's because it is inherently a poor mechanical design. I'm improving it and I'm waiting for some parts to get it running again.

There is an interesting balance required to print out these 'organic' parts. They don't have nice flat planes or straight edges - they are all curves, holes, overhangs, swells and shrinks. To do an overhang you need to have cool extruding temperatures and quick cooking of the extruded plastic so that it doesn't sag; to get good adhesion between layers you need slow cooling and  hot extrude temperatures.  And it really is true that different colors of the plastic need different conditions - mostly because the fillers change the physical characteristics of the plastic. Black is particularly hard to work with. So I think I'll mostly work with white and clear.

So here's some pictures. Here's the printer itself with the control panel in front.
 Here it is printing out part of a Teratorn Humerous. The Teratorn is an extinct eagle with a 15 foot wing span. This bone was excavated at Woodburn (Oregon) high school. It was CAT scanned and translated into .stl files by the University of Oregon where the original is displayed. it is quite a challenge to get this printed - I haven't succeeded yet, but I'm close.
 Here it is printing out Bernie's Scapula
Here is a printed copy of the most complete brain case next to the original. Guess which is which!

Here's a hint - it is the one with the catalog number and the better underside (overhangs are difficult).
Here is a print with the raft (the flat base that goes on the printer bed) and the supports added to hold up the overhangs as they are being made.

 Here's the built-in control panel.

 Here's the base of the Teratorn bones, showing the intricate internal structure captured by the CAT scan. No other copying technique can reproduce this intricate texture.

 And here's the Distal end of the Humerus of the teratorn printed in white ABS. I'll be trying clear PLA so that the inside structure can be seen (somewhat) without slicing it open.

And here is how you do this process. Brown outlines are the traditional fossil prep steps. Green is the scanning steps. Blue are software steps. Red is finishing it up as desired. Lots of complicated steps to this process if you want to do it right!

Finally, here is a video of the printer in action:
Sincerely, Greg Carr

1 comment:

  1. Nice answers in replace of the question with real point of view and explaining about that.Open in a new window