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What is the secret for clean outer walls while printing inner walls first ???

I've always been printing outer walls before inner walls. A few weeks ago, had to print inner before outer because I got crappy small holes (laying on the bed).

At first, didn't notice the loss in quality for the outer walls. When I noticed, I thought the v0.2 had some problems. Until I discovered I didn't reset my prefered wall order (outer first). Reverted, and it made beautiful prints again.

Learnt recently that some slicers default to inner to outer.

How do you get perfect outer walls when they are the last being printed ?

[EDIT] the small holes in first layer most likely are related to textured PEI, as I never had adhesion problems for small features until I switched to textured. Builttack, mirror or smooth PEI, it always worked as expected. Doesn't seem to depend on squish.

Edited by YaaJ
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In my experience, you should almost always print outer walls first. The only time I found it important to print inner walls first is when the print has overhangs that angle outward. In that case, you must print the inner walls first - if you print outer walls first, they could possibly be printed in mid-air with no support. Printing inner walls first will almost always push the outer walls out, making holes smaller than they ought to be. 

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I know that. And it is what I've been doing for years.
IIRC, Cura also had inner first (been using it since v3.xx, could be wrong - seems to me I changed it at this time, then copied/pasted profiles again and again)

Prusa Slicer and Super Slicer (and maybe Slic3r) print inner first by default (AFAIK)  and have line width set to a value higher than the nozzle diameter (by 10% or so), and many users are happy with default settings.

Reason why I'm asking how these slicers produce great prints, while they print inner first. This is the question. It is not about the choice inner/outer.
(I use Cura, and some missing parameters in all Slic3r forks make me stick with Cura - anyway, Arachne being Ultimaker work, all these slicers using Arachne, they now are basically powered by Cura)

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I would suggest tweaking your line width. If your line width is not an exact multiple of the thickness of your walls, Cura or any other slicer will try to compensate by either adjusting line width on the fly, or use solid infill to fill in the gap. The best way to print walls is to have an exact multiple of line thickness without any remainder. For example, if the wall thickness of your part is 1.8 mm, you would want a line width of 0.45, and not 0.40, because 0.45 goes into 1.8 exactly 4 times. You can also adjust the inner, infill, and outer line widths in Cura, to obtain an exact value. Also, printing the outer line width at a thinner value may help. You will have to experiment to find the right combination.

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5 hours ago, SuperBoppy said:

Cura or any other slicer will try to compensate by either adjusting line width on the fly, or use solid infill to fill in the gap

Arachne does this exact job. It doen't just try to do it. It does it adjusting intermediate wall widths as continous infill. And it does it to perfection.

It was introduced by Ultimaker Arachne Engine and Cura 5.0.0, reason why all other slicers are now using Arachne engine, and there's no more need for these nasty calculations (been using 7 quick change tool heads with different nozzles from 0.3 to 1.2, and had headaches while CADing for a nozzle or another). This was before Arachne (that was available as a alpha fork long before 5.0.0 came out)

Was a game changer when it was introduced, at least for designing enclosures. And, believe me or not, I did many testings about that, including suggestions by the Cura dev team on Github, and wasn't the only one, by far.

This has nothing to do with the wall printing order.

In Prusa Slicer defaults, I see :

- walls are 10% larger than nozzle ID (0.44 for 0.4) ; benefit from the nozzle tip OD speading plastic
- outer walls are a bit narrower than inner and intermediate one (0.42 for 0.4)

- inner walls before outer walls

Next print, I'll try the Prusa defaults

inner first
line width = nozzle ID + 10%
outer wall = nozzle ID + 5%

[EDIT] reprinted a part that was printed outer to inner. Using Prusa settings. Just crappy... Inconsistent walls, looking like micro layer shifts. Will have to compare the same part, one being sliced with Cura, and the other with Prusa (never used it : never could use Slic3r forks, whatever they are, and have been hating Slic3r because of its GUI. Cura fanboy.

Edited by YaaJ
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Just printed ABS (real ABS) on my homebrew actively heated bed slinger, with true ABS. The cheapest I found on Amazon...

Used the Prusa default settings (inside to outside).

Much better results. Inside to outside much better than outside to inside with eSun on the Voron 0.2.

My conclusion ? ABS+ by eSun is the worst material I ever printed. Purchased it because it is the official Voron ABS... Not only real ABS has much better layer adhesion, but it also can be printed inside to outside with excellent results.

Why does the Voron Team recommands this crap ? Don't tell me "because it can be printed on a open Prusa".

As a ABS noob, I'm really hangry.

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Was sure I read that it was the recommanded ABS... until now. Maybe because it is widely used, and considered as good enough ? Don't know...

And was wondering why, because of the terrible layer adhesion. But it doen't warp at all, and looks great.

Will reprint everything later, as soon as the 2.4 is operational (will take time !)

Thanks for pointing this.

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On wall ordering, make sure you dial in your extrusion multiplier (EM) (flow in some slicers).  See the Ellis tuning guide.  If you are over-extruding, then wall order is just an attempt to compensate by redirecting the excess, and can only do so much.  Better to not have excess in the first place.  This may not solve the problem, of course, but it's where I'd start.

As far as eSun ABS+, I'm with you.  I got Polymaker for my V0.2 parts, but grabbed a roll of eSun ABS+ to practice with, based on a Nero 3D video or two which mentioned it.  I was able to print with it just fine, but it had terrible layer adhesion, the temp tower just fell apart in my hands.  I wasted most of a week trying to figure out if my bedslinger simply wasn't working right, because all temps of the temp tower looked identical, even when I ran the temps up to the max, and all levels were weak.  In frustration, I threw the Polymaker on the printer, and it Just Worked.

So I used up the eSun ABS+ roll on decorative items, and for that it worked just fine.  Like I said, it was easy to print with, and it did have a nice matte surface finish.  I just don't trust it for anything functional.

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15 minutes ago, dshess said:

Better to not have excess in the first place.

And the infill overlap most likely has a huge impact ! Also "connect infill lines" that adds a random interrupted inside wall. Everything piling up from inside to outside.

Very rarely use inside to outside, reason why I forgot to restore outside to inside after using it (small holes that didn't stick well on the build plate), and thought the 0.2 had problems.

Thinking of more technical materials, such as filled ASA, or PC.

Edited by YaaJ
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Printed two Kobayashi's (very old print-in-place fidget) ; the daughter wanted her 7 years old one replaced (PLA)


Voron 0.2 ; two materials.

On the left : eSun ABS+ ; it didn't fall apart after removing it from the builplate. It felt apart while printing !

On the right, the cheapest ABS from Amazon ; didn't even have to break it in. Beautyful.

LA is calibrated for ABS+, didn't change for the plain ABS (bulges a bit on corners). 250/100°C, 0.2mm layers (0.14 recommanded)

(of course, being ABS, and printing outside to inside, with thick layers, overhangs are not the best, but it is perfectly functional, works smoothly, and will not fall apart.


Got a roll of ASA. Will see, at first with the current profiles (Elli's calibration takes time !).

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