Yesterday I decided it would be fun to create a 3D model of a pyramidal frustum. I have no idea how this popped into my head, but I've decided to blame it on my friend Mike P., from way back in junior high and high school. Mike had a great knowledge of the esoteric and was quite a good artist. It's quite possible that while we were playing Car Wars one day he made an offhand comment like, "If I designed a house it would be a pyramidal frustum." That'd be just like Mike.
So yesterday I decided to model my own pyramidal frustum, and because no project can be left simple, I decided to embed Fibonacci spirals in the faces. (Plus, anything with a Fibonacci spiral is automatically +5 in Mysterious, right?) You can see the OpenSCAD code for the modeling if you like, but here I'm going to talk about dialing in the FlashForge Dreamer settings to make a nice print.
The four prints in the photo are ordered left to right from first printed to final print. The first print's pretty bad. The copper layers are really uneven and the edges are stringy. The blue spirals look terrible -- the second extruder leaked blue filament everywhere, yet somehow managed to not fill well in the print itself. Go figure. I'm using Simplify3D to slice and in that first print, the Hatchbox bronze PLA was set at 180 while the Metalink blue was set to 200.
(My Dreamer has upgraded nozzles which tend to make Hatchbox PLA print at lower temps than the original nozzles. However, I just got this Metalink filament recently and used it to print all the sea tiles for a Settlers of Catan set quite nicely at 200C.)
For the second attempt I decided to turn on retraction and coast at end. I was trying to avoid using a priming pillar because pillars really add to the length of a print. I find that the priming pillar needs to be 10 or 12 mm square, minimum, to NOT break away from the print bed. When your pyramid is 30mm square at the base, that priming pillar adds significantly to the overall print time. So, retraction on to 2mm, coast at end of Simplify3D's default .2mm. Result: a still very crappy looking frustum.
Third attempt: increased the retraction to 5mm and the coast at end to 2mm. (Yeah, that's a big jump in the coast value.) I also lowered the temp on my Metalink filament to 190, since it was still leaking little drops of blue all over the place. The threading seems to have gotten even worse in this one.
Fourth try: all right, I'm turning on the ooze shield. I use this feature a lot when I print dice, since it helps prevent cross-contamination of the filaments. I'd been trying to avoid this since it adds to the print time; not quite as badly as the prime pillar, but noticeably. In this case, the print time went from 36 minutes to almost exactly an hour. Yikes.
On the other hand, the ooze shield made that fourth frustum come out far nicer than any of the previous attempts. I did leave my retraction and coast set the same as the third attempt, but the ooze shield clearly made the biggest difference. I'll have to experiment further with tweaking the retraction, extra restart distance, and other related settings. For now though, when someone has a critical need for a pyramidal frustum, I'll have to stick with the ooze shield.