Tuesday, April 21, 2015

Printing more skulls and grinding out the bones

There has been two main activities in Bernie's 'life' - making more full-size copies of the skull, scanning more bones and grinding out new ones. I have just completed the second full-sized skull, this one in white PLA. I think white gives you the expectation of old bones, although Bernie's bones are actually dark grey.

I found that printing the skull in one piece to be rather impractical. It takes over 3 days, and the longer the duration of the print the more chances to have a failure. Also, the standing-up position requires a lot of supports that eventually will become waste. So I have split the skull into two halves - front half and back half - and print them based on the flat 'cut' surface. It cuts the print time to about two days, one per half, and had much less waste and much more mechanical stability during the print. So here is the view of the first front half through the glass build plate before it was removed.

Of course, after you print two halves you have to glue them together - superglue to the rescue (again). 

The assembled skull is really awesome - like an alligator I have requests for about 5 of these already. Here is a couple of movie clips showing the machine in action printing these half-skulls: 

As far as scanning, that is proceeding with about two bones per week being scanned. We have just sent up the second shipment of bones to the U of Alaska, Fairbanks, to Pat Druckenmiller. His graduate student, Eric Meitz, will be writing up the classification of this animal as a Master's theses. I am only sending up scanned bones so we can make copies down here as desired. 

As for grinding out bones, we have found a very nice combination. A couple of months ago we discovered a rounded shell freed by an errant hammer blow. it wasn't quite like an ammonite nor nautiloid. After preparation, it appears to be some type of a slipper snail. And in the open of the skull we found two centrums and two ammonites! very cool combination

Last of all , I have now prepared the fifth (5!!) braincase. This one is more broken than the others, having lost most of one side. However this opened up the brain chamber and allowed me to almost fully prepare the hole that the brain sat in. It is amazing how big the hole is inside one of the braincases!

Last of all, my wife Peggy and I will be taking an extended trip to Alaska starting in mid-May. So I may have one more posting before then. I don't intend to make this blog a travelogue, so I'll limit my posting to fossils we find during the trip . 
Sincerely, Greg Carr

Tuesday, April 7, 2015

First full-sized print of Bernie's skull!

I have finally gotten confident enough that I attempted to print out a full-size skull. This includes both halves, something not seen for about 230 million years. It was really a marathon. It took a total of 76 hours, nonstop,  and used almost a full roll of PLA plastic. If I used ABS it would take the same amount. At times I had to apply superglue to the supports as it was building (still moving, dodging the moving extruder head) to keep the slender supports from wobbling and breaking off. I definitely need to have the model cut in half so that I can print it flat side down so it would be more stable and require less supports. So here's some pictures:

Several hours after printing started, you can see the 'raft' on the baseplate and the supports the slicing program adds to hold up overhangs.
 Here is one of the problems - the back of the skull has projections . In this build, these projections start out small and grow. However when they get about 1/2 inch (2cm) they want to flop over and break off. I had to manually intervene with superglus and glue them in place WHILE IT WAS STILL PRINTING! Pretty crazy, right?
 Still ongoing - after about 1 day.

 I don't know what happened to cause the large discontinuity across the print - perhaps the filament jammed?
 Here's a shot from the side after almost 2 days of printing.
 Here it is almost 3 days of printing. Still hanging in there.
 Here it is finished after 76 hours of printing - 3 days and 4 hours.
 Here is a top view before I removed it from the printer.

 And finally here I am holding up my trophy! Glass build plate still attached.What a monster - I'm glad I wasn't around then!

Sincerely, Greg Carr