I'm trying to print a part with thin walls. I've designed it with wall 1.2 mm thick, so that I should get three 0.4 mm lines. This works just fine for the straight lines, but for the radiused corners, Cura 4.3 insists on trying to print infill. This infill is only added where they are going at a tangent to the curve, so it alternates corners on alternate layers.

enter image description here

Worse, it prints the segments entirely out of order, which adds lots of travel and hence print time.

I've tried setting the infill to 100 %, setting the wall thickness directly to 3 rather than the default 2. I've tried reducing the wall thickness by 0.2-0.3 mm. I've tried a few other things too - all to no avail.

Some layers it gets right: enter image description here So why can't it get them all right??

I presume that this is probably caused by the fact that the curves are actually a series of straight segments, and so the centre gap between outer 0.4 mm walls will not be exactly 0.4 mm all the way round, but is there any way to just force Cura to print three lines all the way round?

Now, I know that this will print OK, but the corners will obviously look messier than they need to, and this is not the first time I've come across this problem. I'd like to get this fixed.

I have found a similar question, but it's for an older version of Cura, and the recommended solution of 100 % infill doesn't help.

  • $\begingroup$ Hi, SiHa. Have you tried setting extrusion width to 0.39mm, to circumvent rounding issues? Please try this and post your results. And welcome to the site. $\endgroup$
    – Davo
    Jan 17, 2020 at 20:27
  • 1
    $\begingroup$ @Davo Really!?! It was that simple? Thank you - it's perfect. If you post this an an answer, I'll gladly accept. I'd be grateful if you could give a bit more explanation a well. When you say 'rounding errors', what exactly do you mean. I'd have thought that 0.39 would be more likely to cause errors than 0.40. Clearly I'm wrong, and would love to understand. $\endgroup$
    – SiHa
    Jan 17, 2020 at 20:33

1 Answer 1


Even though each path, in theory, is concentric around the center point of the arc, the pathing does not always work out that way - especially around corners and radii.

While your 1.2mm walls should always allow for three 0.4mm paths, if the slicer rounds down the overall thickness to 1.19mm, it will not detect enough room for three 0.4mm paths - but three 0.39mm paths should still fit, even if the slicer determines the thinnest part to be 1.17 mm.

  • $\begingroup$ @SiHa the other way would be to design the part "3 line widths +0.05 mm" to force it. $\endgroup$
    – Trish
    Jan 17, 2020 at 23:26
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    $\begingroup$ This really needs to just be fixed in Cura. It could and should just vary line width as needed. $\endgroup$ Jan 18, 2020 at 2:01
  • $\begingroup$ @Trish Thanks - yes, I get it now. I had it in my head that the curves were creating gaps which were larger than 0.4mm, and was reducing the overall width to try and force Cura to just lay down a single line. Now I understand, it should no longer be a problem. $\endgroup$
    – SiHa
    Jan 18, 2020 at 10:07

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