Thin wall settings?

[printbot 1]

Hi, I now have my Ultimaker pretty much running nicely and think I have my head round most of the settings but could do with a hand on thin walled prints.

How do I best work out which settings to use for say a 1mm walled object printed at 0.1mm layer height - I tend to get an inner and an outer wall with nothing joining them whereas I'm keen to print a solid 1mm wall?

I suspect there is some interplay between different variables going on but not sure - if anyone has some pointers to help me on my way it would be much appreciated :-)

 

[illuminarti 18]

Cura has some problems with thin walled objects, which can tend to lead to gaps in narrow parts.

If you have control over the model itself, and it's something that needs a uniform thin wall, like a box or a cup, its generally best to have the model be a solid block, rather than actually modeling the inside and outside surfaces of the wall. This way you have more control over the printing by specifying different wall thicknesses in Cura, and setting the infill to 0%, so you just get the outer wall.

If your model actually represents the thin walls in its STL, then things get more complicated, because Cura has to try to fit the wall thickness you request in Cura within the limitations of the space in the STL file.

Generally speaking, you want the wall thickness to be an exact multiple of the nozzle width, so that the wall gets printed just using loops that touch one another, without leaving a gap.

For instance, if your nozzle width is 0.4mm (the UM default) then a 0.4mm thick wall will use 1 pass, a 0.8mm wall will use two passes, etc. If your wall thickness is specified as 1mm, while your nozzle is still 0.4mm, then it might do two 0.4 mm loops, and then be left with a 0.2mm gap in between which is too small to fill. In this case, what Cura actually does is pretend that the nozzle is 0.5mm wide, and try to do two 0.5mm wide loops. But due to a bug, it doesn't get it quite right... (see http://www.extrudable.me/2013/04/08/walls-and-nozzles-and-cura-oh-my-or-quickprint-is-broken/)

So what to do... well, ideally, make the walls be an exact multiple of your (0.4mm) nozzle width. Either by updating your STL if the wall thickness is modeled into it, or by setting a 0.8 or 1.2 mm wall width in Cura. If it's critical that the wall be 1mm thick, or that's what's in the STL and you can't change it, then try setting your nozzle width in Cura to 0.5mm, to preserve the exact ratio. (If you do it manually, it avoids the bug mentioned above). Cura will then extrude slightly more plastic which will get spread out under the head to make two 0.5mm beads of plastic, for a total width of 1mm.

Or, the other alternative is to use a different slicer - perhaps Kisslicer - that doesn't have the problem with filling small gaps, and fake nozzle sizes. But, to be honest, Cura can probably - still work for you: just adjust the nozzle size and or wall thickness so the latter is an exact multiple of the former.

 

[gr5 2,234]

The new slicer coming out with cura supposedly fixes this problem.

Basically, the new cura slicer and kisslicer fill that gap even though it is thinner than the nozzle width. It sort of underextrudes on purpose in that small gap and it just pretty much works. But the slicer with the current cura (skeinForge aka SF) doesn't handle thin walls and usually leaves it all empty.

 

[printbot 1]

Hej illuminarti and gr8,

Thanks for explaining this so clearly, it is very much appreciated. I now have enough info and options to make this work I'm sure - now I need to tinker and learn to get the best result :-)

Any idea when we will see the new CURA software released?

Cheers.

 

[Daid 306]

Most likely the new software will be released next month.

 

[Boggy22 0]

Hi guys,

Sorry for resurrecting this thread but I'm having the exact problem in Cura 2.3.0. Is there a setting I should change to actually get completely filled thin walls?

I attached a screenshot(although the infill is at 25% in the pic, the same thing happens at 100%)

Thanks in advance,

B

[IRobertI 521]

See the posts by bagle-orb in this thread:

https://ultimaker.com/en/community/24633-there-is-no-fill-gaps-between-walls-option-in-shell-options-as-stated-in-the-tutorials

(I think he meant to say 2.4, not 2.3)