Printing hollow with a clean inside?

[mrbanana101]

Hi all - I'm printing an assortment of hollow models, 2 - 4 outline layers thick. They're required to be hollow, thus printing them at 0% infill. The outside surface of the print is coming out just fine, but as this will be used as a mold of sorts, I'm actually only concerned with the quality of the inside of the print. The problem is, if "Bottom Solid Layers" is set to anything other than 0, those extra layers appear on the inside of the mold and destroy the inside surface detail, but printing without bottom solid layers will of course lead to lots of big gaps in the print. I was hoping that setting the Outline Direction option to "Outside-In" would solve my problem, but no luck.

Is there anyway to print hollow (0% infill) prints with a clean, detailed inside surface to be used as a mold (even if it means the outside surface will be messed with). Hopefully this question makes sense. Thanks!

(btw, I'm trying to avoid the route of printing a mold as a big cube with the object subtracted as a hollow cavity inside of the cube, so any suggestions would be greatly appreciated!)

[Mogal]

Usually, one prints the inside layer first, and the outside layer at 50% speed.
Can you reverse that to print the outside layer first, and the inside layer at 50% speed?
See if that works?

[mrbanana101]

Hey Mogal, thanks for the reply! I'm new to the forums and never got a notification about the reply, I'll have to keep that in mind.

Unfortunately, printing the outside layer first then the inside (by setting it to print Outside-In) didn't make any noticeable difference, also attempted adjusting the speeds. I spent awhile and think I may have played with just about every option in S3D with no success, so it sounds like I might have to rethink this whole approach.

Not sure if I'm overlooking something or if this really isn't the way to go. thanks!

[greybeard]

Your post made me curious so…

I loaded a simple solid block (in this case, it has a Hex shape).

I set:

Infill = 0
Bottom Layer = 0
Top Layer = 2
Shells = 2
Height (z) = 0.3

Bingo! Screenshot attached… View from the bottom shows it hollow with no bottom surface/layer.

I can’t comment on your part/shape…

[zemlin]

I believe this might be the change you're looking for:

[mrbodiddley]

I found the same wired behavior when printing solid objects with 0 top layers and 0% infill.

This is with 3 bottom and 2 perimeter:

What I found is, this appears as soon as I have >2 bottom layers.

It is gone with 2 bottom and 2 perimeter:

Might this be a bug or am I missing something? Hopefully this is seen after such a long time

[parallyze]

Might this be a bug or am I missing something? Hopefully this is seen after such a long time

Oh, this came up just recently in another thread: viewtopic.php?f=9&t=15238

It's different in v4.1.2 vs. older releases but still there doesn't seem to be an easy "fix" to avoid it... :-/

[mrbodiddley]

Thank you parallyze, I'll follow up in the more recent one. Unfortunately the amount of bottom vs. perimeter's doesn't do the trick on other objects.

[dkightley]

There's another current thread chewing this very same issue.

The bottom line is described in my post here: viewtopic.php?f=9&t=14020&start=10