Thursday, September 22, 2016

Iron Dragon

While getting some other things at a craft store, I came across a kit for providing an iron rust finish to any surface. Put on a layer of iron-bearing paint, then squirt on some kind of rapid oxidizer. I thought "Hey, I should print something out for this." And so I did. And this is what I got:

Not bad, I think. It's lightweight plastic, but I'm afraid to drop it on my foot.

The dragon-head door knocker I got off of Thingiverse was, in the event, really hard to treat. It's a very complicated shape, with lots of little nooks and crevices, and both the primer and the iron paint were quite thick, so it was difficult getting it completely covered. The "activator" sprays on, though, so that wasn't a problem.

There was also a problem with printing. The design is perfectly good, but my printer kicked out about an hour before finishing the job. I'm guessing a power fluctuation on our old wiring or something. Anyway, I was able to measure the height of the printed portion with the digital micrometer, fire up netfabb, slice off the unprinted section from the design, print that part off, and superglue it on. It went much better than I expected, and I can't find the seam even though I know exactly where it should be.

Sunday, September 18, 2016

The Burning Bed

...well, a bit warmish, anyway.

A persistent problem in 3d printing is warping, bowing, and curling. The first printed layers in a 3d printed item cool down sooner than the upper layers and shrink, pulling of the print bed and curling up. I've tried all the usual remedies: a combination of painter's tape and hairspray on the print bed to keep everything stuck down, printing with rafts and brims added by the printing software, and so on. And they never really worked out. Here's a typical example:

This is one of the walls from my beloved DIY Castle Panic set. It's lovely, but the bottom curls significantly. The wall portion is about 21mm thick in the middle, but around 19mm at the ends, leading it to rock and spin easily when placed on the board. And that's over a length of under 7cm.

Here it is compared with something I just printed out, the base for a dice tower.

I'd post some kind of comparison of how much it curls over that distance, but here's the thing: it doesn't. There's no notable curve over its 18cm longest dimension. The difference is in the hardware. I finally bit the bullet and got a heated bed for my Printrbot. While it took some work to get all the right settings dialed in (some fiddling to get the self-leveling bed recalibrated, bed temperature to 50C, a layer of glue stick on the kapton tape, and no brims or rafts; they just waste time and filament now), and it's not technically necessary for the PLA filament I usually use, the difference is quite stunning. Indeed, I'd basically recommend that anyone getting into 3d printing spring for the heated bed up front. It makes one of the most annoying problems in 3d printing go away instantly.