How to make the lower half of a standing coin-like structure smooth and circular?
 
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How to make the lower half of a standing coin-like structure smooth and circular?  

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prusanewuser
(@prusanewuser)
Honorable Member
How to make the lower half of a standing coin-like structure smooth and circular?

Hi, whenever I print standing coin-like structure using PETG, the lower half of the circle that touches the support (the part highlighted in green) does not look smooth and circular. The lower and upper halves of the circle also do not look symmetrical. Is there any good way to solve this problem? Also, are those parallel thin straight lines part of support that can be removed or part of the model? Any good way to avoid having that?

This topic was modified 1 year ago by prusanewuser
Posted : 17/06/2020 3:05 pm
bobstro
(@bobstro)
Illustrious Member
RE: How to make the lower half of a standing coin-like structure smooth and circular?

Outward sloping undersides are going to be difficult with current consumer-grade FFF 3D printing technologies. Severe overhangs need support, and for support to be removable, there has to be a gap between the support and supported services. This means that the layers immediately above the support are literally printed in air. The resulting extrusions are round due to squish, and sag slightly, resulting in that ugly underside.

Your options are limited to living with the results and doing some post-processing to clean up the finish, or re-orienting your parts to avoid the issue. If printing a large coin-like piece, it is probably easiest to split the print up so the coin can be printed laying flat for good edges, then assembled with the supports after printing. 

Depending on your parts, you may be able to model in some clever supports into the STL itself. Maker's Muse has a good YouTube video series on this topic. 

My notes and disclaimers on 3D printing and miscellaneous other tech projects
He is intelligent, but not experienced. His pattern indicates two dimensional thinking. -- Spock in Star Trek: The Wrath of Khan...
Posted : 17/06/2020 3:27 pm
prusanewuser
(@prusanewuser)
Honorable Member
Topic starter answered:
RE: How to make the lower half of a standing coin-like structure smooth and circular?

@bobstro

Thanks. I used to use those expensive Stratasys uPrint printers. Don't recall having this issue but those filaments and build plates are crazy expensive.

By post-processing, do you mean sanding? Is it worth to buy those electric sanding tools?

I tried another orientation by lading the coin-shape flat on the build plate. However, it caused other issue in other part of the model.

Posted : 17/06/2020 4:23 pm
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