Saturday, 6 August 2016

More printing success than you can shake a piece of filament at

After cleaning the stripped filament from last time off the hobbed bolt, I printed the phone cover with my regular filament, just to see if it would fit. And it does! My calibration is great! My design, however, needs a bit of tweaking, but that was exactly the point of this print. The bottom holes should be a bit higher, the audio jack a bit further right, and both possibly enlarged. I'm quite amazed, though, that the overhang for the USB-C jack came out so nice - that's without any support:

The hole on the side needs a bit of enlargement, and the sides of it should be slanted for easier access:

On the back, there is a little bit of offset to the left, and the hole for the fingerprint is up too far. Plus, the sphere I used to make the fingerprint scanner easier to touch left a few strands. That might just be the effect of having a part that's thinner than the layer height. I can reasonably make it more steep.

Most importantly, at the very start of this print, I caught the extruder skipping a few steps, and just to attempt to save the print, tightened the idler screws somewhat, to where the springs are almost fully compressed. That helped! So now I know that the stripping has been partly due to the idler being too loose. That clears up one of my remaining questions.

After that, I printed the AAA battery dispenser again, this time at 90% scale. Unfortunately, part way up it the hotend came a bit loose (the mounting system is crap and I want to print a better one), and I had to fasten it again while printing. The result can store batteries, but isn't as nice, and tends to have the batteries go sideways:

Having noticed the very nice overhang on the phone cover, I thought it'd be nice to have a test piece for overhangs. So I maded one (shared on Thingiverse):

Overhang test with the overhang width in mm.
This shows that I can actually do up to 18mm of overhang, which is pretty incredible. It also shows "ringing", especially after the letters, which I should fix. While most troubleshooting guides seem to blame speed or acceleration settings, I think in this case the slightly loose hotend may be to blame.

The back side of the test piece has circles, where while the overhang is technically smaller, the ends fall down, making them a bit unclean:

I tried also doing this test without my fan running, to see what difference that made. Not quite as much as I expected, but still there's a lot more drooping:

Closeups, first without fan:

Then with fan:

The difference is striking. Having a fan is definitely helping. And this is just with a simple front-mounted fan, no fancy ducts. I have an idea for a fan duct setup with the fan mounted separately and blowing through a tube, but haven't gotten around to it yet. That would at least solve a bunch of annoying mounting issues. It might be more easily done with the radial type fan, possibly mounted on the left side of the extruder motor. The "ducts" could be a wide ring with four little blowers instead of a hotend-specific circle. The quality I'm getting from just blowing in the side tells me that getting every last drop of air placed just right is less important than actually being able to easily mount it. Plus, I want to be able to see the print in progress.

I also finally got around to fixing the loose wires I had had hanging around, getting rid of the last crocodile wire. It's better, and I won't have to worry about the fan wires falling down and catching on the corner clamp, but I still need a few cable ties to make it perfect:

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