Maximum Diameter Without Supports

[desman]

What is the maximum diameter hole size of a hole running horizontally through a part that you would print without using supports. In abs and or pla. Trying to get an idea of where to cut back on using supports in prints. The holes and slot in this print being a good example. Tholes are about .2 diameter and the slots are .15 wide. The holes were not to bad to clean the supports but the slots were not easy.

[Jules]

You def. don't need to use support in those slots. The M2 will bridge across an even (horizontal) gap of up to about five inches. (I know that for certain because i just did it a week ago, accidentally.) The holes will sometimes sag a little at the top if you place the item to be printed so that the direction of print runs parallel to the hole. You can avoid that by turning the print on the bed to a 45 degree angle before printing, and when using PLA, if you hit it with a lot of fan, particularly on overhangs. (I use a little desk fan in addition to the one that comes on the machine.)

[desman]

Jules thank you I will try it with the part rotated.

[jimc]

yes i have printed 3" dia tubes sliced in half laying lengthwise on the bed and it prints that with no support. the inside surface wasnt super clean and flawless but it wasnt too bad either. outside surface was perfect though.

[jsc]

For interior overhangs, with PLA and additional cooling, you can get up to 70 degrees with very good bottom surface quality, or 60 degrees with nearly perfect quality. viewtopic.php?f=10&t=2020

Smaller diameter arches will spend less time in the danger zone; most screw sized holes can be printed without any support at all.

[dsharp02]

I've switched to using octagons instead of circles for horizontal holes. The theory is that with an octagon none of the sides will exceed 45 degrees of overhang and then you're left with a single bridge at the top.

Dave

[Jules]

I've switched to using octagons instead of circles for horizontal holes. The theory is that with an octagon none of the sides will exceed 45 degrees of overhang and then you're left with a single bridge at the top.

Dave

Very good idea!

[dsharp02]

I forgot to mention that there is also a reason to use polygons for vertical holes as well when the exact dimensions are important. Nophead has a really good article on the subject:
http://hydraraptor.blogspot.com/2011/02/polyholes.html

Dave

I've switched to using octagons instead of circles for horizontal holes. The theory is that with an octagon none of the sides will exceed 45 degrees of overhang and then you're left with a single bridge at the top.

Dave

Very good idea!

[jsc]

Nophead's polyholes are about horizontal hole dimensions.

[dsharp02]

Nophead's polyholes are about horizontal hole dimensions.

Ummm... no. If you look at his pictures the holes are clearly vertical. The holes are on a horizontal surface, but the holes themselves are vertical.

[edit: I just realized that I may have come off as being snarky ]
I think we're just using different definitions of "vertical hole" and "horizontal hole".

Dave