External faces issues creating solid

The inner top corner of the profile needs the be the radius away from the center of the circle. So start with those two points and draw the shape to match.

Depending on your 3D printer, to get a 6mm diameter hole in the printed solid, you may need to draw it bigger.

My FDM printer has a nozzle 0.5 mm diameter. Because the centre of the nozzle follows the edge of the model drawing, holes come out approximately 0.5mm smaller than the circle that defines them, and the outside of a cylinder 0.5mm bigger.

So offset the inside edge of your FaceMe profile further from the origin than 3mm, by half the nozzle diameter, and make the outside edge of your cylinders the same amount closer, if you want the finished sizes exact (or very nearly so).

However, I donā€™t know if you need to do the same for laser resin bath printers.

Your slicer takes this into account if Iā€™m right!
So the centre of the nozzle should not follow the edge of the model, but half of the line-width offset.
You are right tho that a hole is smaller after printing than the modelled hole.
This is due to the tollerances of your printer and your settings.
It takes some tinkering to get it (almost) rightā€¦
I need to model a gap of 0.2mm to make it fit, so the hole is 0.1mm smaller than modelled and an axle 0.1 biggerā€¦

My slicer is the Lulzbot Mini variant of Cura (latest version 3.6.3).

As far as I can tell, the slicer doesnā€™t itself allow for the nozzle diameter. It still draws ā€˜holesā€™ 0.5mm too small (approx) and outer diameters 0.5mm too big, compared to the original skp or stl file.

No offset I can detect between drawing and nozzle centreline.

What is your slicer that does make the offset?

Cura, latest version but all previous versions I used worked in the same way.
Could be that your slicer works different, but I doubt that!
Maybe some settings are wrongā€¦
As I said, it takes some tinkering to get it right.

And it can also be hardware related.
And firmware related, maybe the steppermotors need to be callibrated.

Do you remember which settings you needed to tinker with? I donā€™t know mine intimately at all, but have indeed had some troubles (mainly getting the wrong default printer settings when I updated Cura from an earlier version) but also with the Z-offset and Extrusion parameters. And the Z-offset seems to drift a bit from one batch of prints to the next, enough to squash the first layer badly after previously having got it right.

Iā€™ll maybe try the Lulzbot Forum again in the light of your comment, to see if I can find what ā€˜offsetā€™ setting there might be. I do know that one of the parameters is the nozzle diameter, which I thought was correctly set. But Iā€™ll check again.

This depends on where the problem liesā€¦
I remember a lot of trial and error sessions but it is some time agoā€¦
First I would calibrate your extruder, there are lots of youtube videos about that.
after that I finetuned it by printing a 20mm cube in vase mode, measure it with callipers and adjusting the flow setting in cura by a few percent. Then printing another cube and so on and so on until I had a cube with a linewidth of exactly 0.4mm. (if you print in vasemode youā€™ll get a single wall line witch is easy to measure with callipers)

Z-offset doesnā€™t drift, your bed does!
Z-offset is a setting on the printer, once set it stays that way until you change it.
Your bed however can ā€œdriftā€ and youā€™ll have to level it again. Sometimes the springs are to weak to hold ā€œthe settingā€ firmly.
And after leveling your bed you probably have to adjust your Z-offset because leveling is done by hand and not consistant.

Indeed, the nozzle diameter is a setting in the slicer. But only to calculate how much filament has to be pushed through to get the linewidth you specify.
The linewidth (yet another setting in the slicer) is what I believe is the setting that determines the offset from center nozzle to outside modelā€¦

Hope you can make something out of thisā€¦

thanks for those pointers. Itā€™s late here tonight, and Iā€™m busy most of tomorrow, but will follow up.

The Lulzbot Mine does an automatic levelling every time it starts up. Iā€™ll see if thereā€™s any looseness in the bed or the levelling disks

Itā€™s even later over here :smile:
Goodnight John, speak to you laterā€¦

ABL or automatic bed leveling has in fact nothing to do with levelingā€¦
All it does is measure the hight-differences in your bed and your printer can use that to micro-adjust the z-height so your first layer will be at the right height even if you bed is warped.
So, you have to level the bed yourself!! after that adjust the z-offset and the ABL will take care of your bed imperfections!
P.S. My printer also has ABL. Itā€™s a creality CR10 proā€¦

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i love the use of the plane slice to see whats going on there, makes it so much easier to understand!