kerlin
Posts: 3
Joined: Wed Mar 23, 2016 12:04 pm

Support Material - Rough Bottom Finish

Fri Apr 08, 2016 11:30 pm

Any suggestions as to what might be causing such a rough finish on the underside of an object printed with support material?

As a test, I'm trying to print a 25.4mm sphere with auto-generated support material.

Infill %: 30
Inflation: 0mm
Dense support layers: 0
Dense infill %: 70
Print support every: 1 layer

Horizontal offset: .3mm
Upper vertical layers: 1
Lower vertical layers: 1

Support pillar resolution: 4mm
Max overhang angle: 30 deg

Support infill angles: 0
support_structure_20160408.jpg

CompoundCarl
Posts: 2005
Joined: Wed Aug 05, 2015 7:23 am

Re: Support Material - Rough Bottom Finish

Sat Apr 09, 2016 1:21 pm

It's quite difficult to print a perfect underside of a sphere like that when you are using the same material for supports as for the part

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jimc
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Location: mullica, nj
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Re: Support Material - Rough Bottom Finish

Sat Apr 09, 2016 4:06 pm

Yes, avoid support at all cost. Split your model in the center, place flat side down, print then glue together. Undersides of supported areas always look bad compared to the rest of the model.

JohnPowell
Posts: 4
Joined: Wed Apr 06, 2016 6:58 pm

Re: Support Material - Rough Bottom Finish

Sat Apr 09, 2016 4:56 pm

https://www.youtube.com/watch?v=koCVOsRA6Bc
check out this video and it may give you the answer you need.

zemlin
Posts: 358
Joined: Mon Feb 01, 2016 11:36 am

Re: Support Material - Rough Bottom Finish

Sat Apr 09, 2016 11:43 pm

Try some dense support layers. I like to run at least 4 at 85%
The underside will never match the top, but dense support will help a lot. It's also more of an issue with thicker layers, since you can only define the separation by layer increments rather than an absolute amount (a popular feature request).

I generally run with the max overhang at 50 degrees.

It also depends on the material. PLA cleans up a lot easier than ABS. PETG support also breaks off pretty well. Nylon can be difficult.

zemlin
Posts: 358
Joined: Mon Feb 01, 2016 11:36 am

Re: Support Material - Rough Bottom Finish

Mon Apr 11, 2016 7:50 am

I ran a 25.4 sphere last night just for kicks.
balltop.JPG
ballbot.JPG
Even with high-density support layers and a .1mm layer, the bottom third of the ball is distorted. I suspect it's more thermal that support issues. I'm thinking that if you ran a batch of 10 at a time things might turn out better since the base material would cool more before trying to support the next layer. I could be totally wrong, but if I wanted to print nicer balls in one piece, that's what I'd try next.

Personally, I'm not interested enough in the challenge to print off 10 balls. :-)

If you really want nice, smooth spheres top and bottom, JimC's advice will get you there - print halves and glue them together.

kerlin
Posts: 3
Joined: Wed Mar 23, 2016 12:04 pm

Re: Support Material - Rough Bottom Finish

Mon Apr 11, 2016 7:05 pm

I appreciate the feedback. Dense support structures helped but not significantly. And while I might ultimately end up at a "slice and glue" solution, I'm not ready to give up just yet.

I was also thinking it might be thermal so I turned off the heated platform but, again, the improvement wasn't significant.

So I guess I'm printing 10 balls tonight. For science! :)

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jimc
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Location: mullica, nj
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Re: Support Material - Rough Bottom Finish

Mon Apr 11, 2016 8:33 pm

its not thermal. its because there is a gap between the support and the model. this has to be there so you can remove the support. if not they would be completely fused together.

zemlin
Posts: 358
Joined: Mon Feb 01, 2016 11:36 am

Re: Support Material - Rough Bottom Finish

Tue Apr 12, 2016 7:23 am

jimc wrote:its not thermal. its because there is a gap between the support and the model. this has to be there so you can remove the support. if not they would be completely fused together.
except on mine the ugly continues far up the side of the ball well past where support should be needed. A test piece checking overhang using the same printer set up looked great until almost 60 degrees of overhang. The ball I printed doesn't start printing cleanly until about 35 degrees.

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jimc
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Re: Support Material - Rough Bottom Finish

Tue Apr 12, 2016 7:36 am

Well yes you could have other issues as well. I just meant generally speaking for supported areas.

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