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[Solved] Design for circular holes

tankenland
(@tankenland)
Member

Not sure this question should be posted in this topic. 

I having problem in printing vertical circular hole (circular hole where axis of circle is perpendicular with z axis) as shown below:

image

The printed circle of are not round (oval), and the dimension that I have measure is shown below (sorry for bad skeching): 

image

The top surface of the hole are also terrible. 

image

Any way to improve it except than changing the design? 

Also because of this problem, I am thinking of change the design. Here are a few design I am considering to replace the vertical hole:

Shape 1:

image

Shape 2:

image

Shape 3:

image

Which one would be better? Or Any other shape or recommanded?

 

Regards,

Ken Land

Quote
Topic starter Posted : 01/06/2020 11:35 am
Bob
 Bob
(@admin)
Member Admin

I have already posted my approach to this in the Prusa Forum. And so I'm just gonna post a link here.

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Posted : 02/06/2020 8:17 am
tankenland
(@tankenland)
Member

@lichtjaeger Thank you

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Topic starter Posted : 02/06/2020 8:24 am
Ed Tyson
(@edtyson)
Member Admin

Shape 1

But why can't this be printed horizontally so you get perfectly smooth holes? I cover this more in my book The Ultimate Beginners Guide To 3D Printing that you can find in your members area.

Hope that helps!

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Posted : 04/06/2020 10:59 am
tankenland
(@tankenland)
Member

@edtyson Thanks for replying. I know I can reorientate the part to avoid this problem but sometime there are always some hole cannot be avoid to be printed in this direction. So I want to find some solution that are possible. 

 
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Topic starter Posted : 04/06/2020 11:18 am
Luke
 Luke
(@lmf5000)
Expert Moderator

Hi tankenland,

In addition to Ed's suggestion to re-orient the print whenever possible so holes are printed horizontal (that's how you get best accuracy), you can try the following for cases when printing vertical holes is un-avoidable:

  • Use smaller layer heights so the dimensional difference is less (PrusaSlicer and Cura both support adaptive layer heights so you could have small layers only at the top of the hole where it's critical, so it won't slow the rest of your print too much)
  • Use your Shape 1, with the two 45° lines. 45° of overhang angle should be no problem for practically every printer; in fact most printers can manage a little better than that, say 60° - but some experimentation is needed to find your limit (an overhang test, something like this - https://www.thingiverse.com/thing:1564848 )
  • Print the holes round, and then drill/mill/ream them out to the correct size - for critical dimensions this is the most accurate option. If you want a 100mm hole, design and print a 100mm circle. The actual print always comes out smaller than designed (I predict the real print will be around 99.2-99.6mm on its largest sides if you're using 0.4mm extrusion width). Then use a 100mm spade bit or an end mill to drill the hole out to almost exactly 100mm. It might be a tad larger, but it will be almost perfectly round.

Regards,
Luke

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Posted : 04/06/2020 11:34 am
ThreeDeeDave
(@threedeedave)
Member

@tankenland Hi Ken,

 

Just going to add in my two cents as well. It is a tricky one as you would just hope it would just print correctly!

What might be a good idea is to check out a feature on Cura called horizontal expansion. It basically lets you slightly alter dimensions inside a mesh to compensate for printer inaccuracies. I have never used it myself but here are a few links to check out to see how people have used it:

Video: https://www.youtube.com/watch?v=-jsBI3OeUJQ

Video: https://www.youtube.com/watch?v=UUelLZvDelU updated version

Forum post of how a user used it to minimise flat overhang ares on their vertical holes: https://community.ultimaker.com/topic/25415-cura-bridging-vertical-holes-top-and-bottom/

Hope that can contribute in some way 👍 

Thanks

Dave 

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Posted : 04/06/2020 12:05 pm
tankenland
(@tankenland)
Member

Thanks for everyone for the great answer. Those things really open my eyes !

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Topic starter Posted : 04/06/2020 4:19 pm
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