In my previous post about MeshMixer, I mentioned wanting to print a really cool dragon model, and showed a preview of how MeshMixer’s support engine handled the shape. Some of the folks over on the Ultimaker forums were dubious about the utility of MeshMixer’s support in general for extrusion-based 3D printers, and specifically about whether it would be sufficient to help with printing the dragon. Based on the testing I had already done, I was pretty confident that it would work well, and I really wanted to try it out, so I started doing a series of test prints, culminating in a final 23.5 hour print.
I was asked to print a Dragon as a Christmas present for someone and this one from Thingiverse seemed like a really good candidate. It’s nicely modeled with some good detail, and it also intrigued me as a challenging print.
The wings are thin, and spread wide with nothing supporting the trailing edges, or indeed the surface of the wings themselves. Looking at the few ‘I made one’ prints on Thingiverse, it became apparent that there were probably some geometry challenges with the wings too, which had resulted in most of the prints being rather scrappy, and having ragged holes in the wings.
Preparing the Print
I started by just scaling and slicing the model in Cura, and seeing how the layers view turned out. That made it clear that some of the middle sections of each wing were simply too thin to print, so I loaded the model into Netfabb and repaired the mesh, then took it into Z-Brush and thickened the thinnest sections slightly. At the same time, I filled some more holes and broken geometry in the trailing edges of the wings. Later, after my first test print, I went back in and put tiny flat spots on the tips of the claws arrayed along the edge of the wing, and the tip of the tail, so that they would have slightly more surface to adhere to the supports during printing, in order to prevent them toppling over before they could join up to the rest of the print. Another round trip through Netfabb made sure that the geometry was good, and I cut off the bottom couple of millimeters of the feet to give a flat surface to stick to the print bed.
Next, I imported the model into MeshMixer, and added supports. The settings were basically the same as I outlined in my earlier post, but it took me a few iterations to get the support to the point that it would print successfully all the way to the top of the wings. In a future iteration, I might try using even thicker support pillars, and steeper angles.
Here Be Dragon(s)!
Once that was all set, I sliced the model in Cura, and set it to print on my Ultimaker². This video shows a timelapse of the process… almost 24 hours, condensed into about a minute:
How Did You Do That?
With the model cleaned up just a little bit in Z-Brush, and a ton of supports added in MeshMixer, the actual printing part was then pretty straightforward: I printed it at 35mm/s, with 0.1mm layers at 230°C. The print is hollow – it just has a 0.8mm-thick skin, and zero infill.
The only thing I did that was different from my typical high-quality print process was that I turned down the non-printing travel speed from 250mm/s to 150mm/s, so as to reduce the momentum of the head, and make it less likely that any accidental collisions with the support beams would knock them loose. (In my first three print attempts, supports got knocked loose when the head collided with a slightly curled overhanging edge. Slowing down the moves and strengthening the support matrix helped to get past that issue).
As the photo here shows, the wings were still incredibly thin – less than half a millimeter at the trailing edge, so that the Faberdashery filament that I used was actually semi transparent, despite being quite opaque in normal use.
(The video was recorded on my iPad using the awesome TimeLapse app, and edited in iMovie.)
Final Clean Up
The support struts were removed easily by snipping them apart with a pair of wire cutters, and then bending back and forth to separate the tip from the print. Small, raised circular scars are left behind, and those could easily be trimmed away with a scalpel and sanded flat. Even the very tops of the wings closed in perfectly, adequately supported from underneath by Meshmixer’s struts, so that there was no discernible drooping.
Can I Make One, Too?
Sure! I created a derivative Thing on Thingiverse, and I’ve uploaded the tweaked plain model, and the version with supports already in place. So by all means, download it, and print to your heart’s content!
How Did You Do That?
Well, as I said… I cleaned the model in Z-Brush, and then…. oh… that. The photo?! It’s a single 20 second exposure. I had the printer’s lights on their dimmest setting for 1 second; a flashlight illuminating the outside of the frame for another second or so, and the rest of the time just the dragon, glowing in the dark, as it does. Who needs an Arkenstone, when you’ve got Faberdashery Glowbug Yellow?? In my earlier testing when I first got my original Ultimaker, I’d found it to be a novel, but sightly fussy material. But on the Ultimaker 2, printing hot and slow, it really comes into its own as a first rate printing material in its own right!