Horrible quality on bottom half of sphere shapes...

Ask the MakerGear community for assistance...
minusbacon
Posts: 87
Joined: Sat Sep 12, 2015 2:52 am

Horrible quality on bottom half of sphere shapes...

Post by minusbacon » Fri Oct 23, 2015 10:35 pm

I'm trying to print Megabot from Big Hero 6 for my daughter.

http://www.thingiverse.com/thing:963917

First attempt I printed the file that prints all the parts at once. Three spheres and six other pieces that have a sphere shaped base. Bottom halves of the sphere shapes printed like this..
FullSizeRender 2.jpg
FullSizeRender 3.jpg
Top halves are perfect, even on the full spheres. I figured they printed this way due to nine parts being printed at once. After a layer, each part had time to sit and cool, causing the poor quality. So I tried printing one piece at a time...
IMG_0133.JPG
One side of the bottom half came out nice, other side same as the nine piece batch.

What can I do to get the bottom half print quality better, if anything?

User avatar
Tim
Posts: 1205
Joined: Thu Apr 10, 2014 2:19 pm
Location: Poolesville, Maryland
Contact:

Re: Horrible quality on bottom half of sphere shapes...

Post by Tim » Fri Oct 23, 2015 10:42 pm

Spheres are always a bear. It's just too much of an unsupported overhang. Printing with support will help, but only to an extent, as you need a lot of support for the worst overhangs, and then you'll get some loss of quality where the supports connect to the print. The best thing to do, really, is to print them in halves and glue them together. A tiny seam around the middle beats a horribly messy bottom half any day.

User avatar
ednisley
Posts: 1098
Joined: Fri Apr 11, 2014 5:34 pm
Location: Halfway up the Hudson
Contact:

Re: Horrible quality on bottom half of sphere shapes...

Post by ednisley » Fri Oct 23, 2015 10:52 pm

Tim wrote:print them in halves and glue them together
Indeed! Cut the spherical parts horizontally along the equator, add alignment pins, and you'll never even notice the seam... because it'll look exactly like the horizontal layer lines.

minusbacon
Posts: 87
Joined: Sat Sep 12, 2015 2:52 am

Re: Horrible quality on bottom half of sphere shapes...

Post by minusbacon » Sat Oct 24, 2015 12:10 am

Is it possible to do that in Simplify3D?

jsc
Posts: 1864
Joined: Thu Apr 10, 2014 4:00 am

Re: Horrible quality on bottom half of sphere shapes...

Post by jsc » Sat Oct 24, 2015 12:24 am

Yes: viewtopic.php?f=2&t=150#p1099

Duplicate the model and flip one over. Auto arrange so that they're both sitting on the bed. Move them around if you want in XY to their final locations. Then double click each and lower the z-height of one by the height you want the split to occur at, and of the other by the full z-height of the model minus the amount you used for the other one.

User avatar
Tim
Posts: 1205
Joined: Thu Apr 10, 2014 2:19 pm
Location: Poolesville, Maryland
Contact:

Re: Horrible quality on bottom half of sphere shapes...

Post by Tim » Sat Oct 24, 2015 4:33 pm

minusbacon wrote:Is it possible to do that in Simplify3D?
Simplify3D can do the flipping as Jin mentioned. What Ed mentioned about adding alignment holes can't be done with S3D; you need software that does actual 3D modeling and manipulation for that. A lot of people, unfortunately, put stuff put up on Thingiverse and other 3D repositories that they just drew up with a 3D modeling tool without any particular thought as to whether it's printable or not. I'm hoping that as time goes on, tools will start having the capability to analyze a design for printability. For now, it takes a lot of experience as well as some guesswork to figure out how to make something printable.

I'm surprised that the photo of the printed Megabot on Thingiverse looks so clean. I didn't see any instructions (maybe it was in the video? I hate instuctional videos) or tips or indications of how they made theirs and on what printer and with what filament and settings. Probably it was done with a lot of support and cleaned up afterward. I expect it took them a number of tries to get the right support parameters, too.

Given the state of software and the poor state of designs found in the 3D repositories, it's highly recommended to learn how to use at least one good 3D design tool well. Ed and I like to use the open-source tool OpenSCAD, but there are plenty of good software choices (and a number of threads in this forum devoted to that topic, so I won't go into it here). Most of them will allow you to read in an STL mesh from a file, and then do things to it like chop it in half and put holes in to align the pieces. I'd say that in my experience, about half the models I've found on Thingiverse that I wanted to print are not easily printable as-is, but almost all of them could be made printable just by cutting in half and printing each side separately. A few require a bit more work; only occasionally do they turn out to be hopeless.

swbluto
Posts: 215
Joined: Mon May 25, 2015 7:09 pm

Re: Horrible quality on bottom half of sphere shapes...

Post by swbluto » Sat Oct 24, 2015 7:20 pm

I've learned overhanging inclines at anything more than 45 degrees will always be a bear due to lack of adequate underlying support. Which happens to correspond to half the bottom of the circle.

What I'd do: Print two top halves separately and affix them.

jsc
Posts: 1864
Joined: Thu Apr 10, 2014 4:00 am

Re: Horrible quality on bottom half of sphere shapes...

Post by jsc » Sat Oct 24, 2015 8:56 pm

With sufficient cooling on PLA, I can get up to 70 degrees with fairly decent results: viewtopic.php?f=10&t=2020

User avatar
Matt_Sharkey
Posts: 347
Joined: Mon Oct 20, 2014 3:10 pm

Re: Horrible quality on bottom half of sphere shapes...

Post by Matt_Sharkey » Sat Oct 24, 2015 10:42 pm

jsc wrote:With sufficient cooling on PLA, I can get up to 70 degrees with fairly decent results: viewtopic.php?f=10&t=2020
but if 90 to 70 degrees prints poorly, you will have a bad foundation for the rest. Maybe it will turn out better, but not as good if it was 2 halves.

User avatar
Jules
Posts: 3144
Joined: Wed Jan 21, 2015 1:36 am

Re: Horrible quality on bottom half of sphere shapes...

Post by Jules » Sat Oct 24, 2015 10:57 pm

jsc wrote:Yes: viewtopic.php?f=2&t=150#p1099

Duplicate the model and flip one over. Auto arrange so that they're both sitting on the bed. Move them around if you want in XY to their final locations. Then double click each and lower the z-height of one by the height you want the split to occur at, and of the other by the full z-height of the model minus the amount you used for the other one.
This should be a separate "How To".......I know it's simple, but I can never find it when i need it. (It's always buried in other topics.) And it comes up a lot with new users. :D

Post Reply