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This is how you handle overhangs. :-)
Posted: Thu Jan 21, 2016 5:07 pm
by gestalt73
This is a 75mm tall worm gear from the InMoov project.
It will be used as one of a pair to rotate the torso left and right.
Printed in Octave Gray ABS, 100 micron layers @ 260c
(Updated, I originally said 220c, but that's because I'm also running a PLA job on the other printer. This ABS I usually print at 260c)
For these types of parts, you really need to use cooling fans on all sides, otherwise the far side of your print tends to curl.
Support was used only till the 20mm mark, because the worm blade juts straight out without a taper.
The seam is visible towards the left of the part.
[img]
http://i.imgur.com/Gxr7ZgZh.jpg[/img]
http://i.imgur.com/Gxr7ZgZ.jpg
[img]
http://i.imgur.com/fA2DRjph.jpg[/img]
http://i.imgur.com/fA2DRjp.jpg
Re: This is how you handle overhangs. :-)
Posted: Thu Jan 21, 2016 5:10 pm
by Neptune
That looks amazing! Nice job.
Re: This is how you handle overhangs. :-)
Posted: Thu Jan 21, 2016 5:15 pm
by nitewatchman
Wow, Neat worm!
How did you generate the model? Is the tooth profile developed or approximated?
The print quality is also on the positive side of acceptable!!
Re: This is how you handle overhangs. :-)
Posted: Thu Jan 21, 2016 6:14 pm
by Outsider
It's part of the inMoov robot. A shoulder screw
I just printed that part with no scaffolding. It turned out not to bad.
Re: This is how you handle overhangs. :-)
Posted: Thu Jan 21, 2016 7:14 pm
by gestalt73
This piece was designed by someone else.
I'm not sure how Gael does it, but I've modeled these types of worm gearboxes a few times, and I start with a sketch->revolve for the basic shape (the worm billet), then I'll spiral a perpendicular sketch for the worm profile.
Then (because I'm not an engineer), I'll put the worm and the the draft gear into an assembly, then edit in place until everything fits.
My custom parts turn out pretty well, but a mechanical engineer would have a fit. I never looked up the official way.
So I guess my technique is: "eyeball - approximated"?
nitewatchman wrote:Wow, Neat worm!
How did you generate the model? Is the tooth profile developed or approximated?
The print quality is also on the positive side of acceptable!!
Re: This is how you handle overhangs. :-)
Posted: Thu Jan 21, 2016 7:18 pm
by gestalt73
Nice! Another InMoov builder!
Yep, there's two different worm gears for the shoulder. That one you can get away with no supports. The other one has a lower lip similar to the one for the torso rotate, and you can kinda print it without supports, but it ends up looking kinda sad.
Also, one has/had an interference issue and requires a fair bit of sanding and filing to mate properly. You'll see it and feel it when you hand rotate the worm in the open casing with the gear.
I'm sorry I don't remember which one it was, but when you find it, definitely take the time to file it down to the correct shape.
Outsider wrote:It's part of the inMoov robot. A shoulder screw
I just printed that part with no scaffolding. It turned out not to bad.
20160121_160310.jpg
Re: This is how you handle overhangs. :-)
Posted: Fri Jan 22, 2016 11:24 am
by Eaglezsoar
One nice print job! Very good work!