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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.

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  • $\begingroup$ 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 at 20:27
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    $\begingroup$ @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 at 20:33
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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.

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    $\begingroup$ Ah. I hadn't thought of it that way. Thanks again! $\endgroup$ – SiHa Jan 17 at 20:49
  • $\begingroup$ @SiHa the other way would be to design the part "3 line widths +0.05 mm" to force it. $\endgroup$ – Trish Jan 17 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. $\endgroup$ – R.. GitHub STOP HELPING ICE Jan 18 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 at 10:07
  • $\begingroup$ Hi @Davo, I noticed you committed to the Drones proposal on Area51. Since you are into 3D printing, I wonder if you might also consider committing to the Materials Modeling proposal? We could really use the help! $\endgroup$ – user1271772 Jan 24 at 21:32

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