print dimensions question

[Daniel Rosen]

I’ve been 3D printing for a while, and I’m still trying to understand how printers manage to hit such precise dimensions. For example, if I want to print a 1 mm-wide line using a 0.4 mm nozzle, the printer would need to lay down two lines (0.8 mm total) and then an extra 0.2 mm on top of the edge of the second line.

So my question is: does that extra overlap push material upward in the Z-axis? Where does that extra plastic actually go?

[Jody Harris]

The Arachne engine was a HUGE step in precision.

https://all3dp.com/2/cura-arachne-superslicer-prusaslicer-explained/

-j

Think carefully

On Monday, December 1st, 2025 at 12:20 PM, Daniel Rosen <dgros...@gmail.com> wrote:

I’ve been 3D printing for a while, and I’m still trying to understand how printers manage to hit such precise dimensions. For example, if I want to print a 1 mm-wide line using a 0.4 mm nozzle, the printer would need to lay down two lines (0.8 mm total) and then an extra 0.2 mm on top of the edge of the second line.

So my question is: does that extra overlap push material upward in the Z-axis? Where does that extra plastic actually go?

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[Daniel Rosen]

Thanks for that. I learned something new!. I could not find the explanation of where the extra plastic go?

[Bryan Eckert]

Daniel, Arachne takes into consideration how much you can vary the line width due to over/under extrusion. It wouldn't lay down 2 .4 lines then try to fill in the gap, it would just lay down two .5 wide lines instead.

Which also means you can use a larger nozzle like a .6 and get details you would normally see out of a .4 nozzle, and really speed up print time.

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[3D Printing Tips and Tricks]

Yeah… I ran that way with the .6 nozzle for almost two years until I finally figured out that the fine threads I kept getting were because of the nozzle. I switched back to .4 standard and all the threads went away for all materials.