Having trouble understanding z height steps
 
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Gery S.
(@gery-s)
Member
Having trouble understanding z height steps

Hi community,

i try to print the first layer at 0,3mm with a overall layer height of 0,2mm (0,4mm nozzle).
The first layer height is at 0,3mm second layer is at 0,592mm (+0,292) and third layer will be at 0,650mm.
I don't it get, why!!
At the third layer the printer already prints a litte in the air, causing the filament to drags over the raft, it won't stick and won't create a good outline.
Since i'm not able to upload 3mf and gcode files:
test.gcode https://drive.google.com/file/d/1W17Sw6852kldHYY1_9kcxOUsmklqO4aP/view?usp=drive_link
test.3mf https://drive.google.com/file/d/1SIH5lou17XW7isadtyH6ZcaCmJMFEJ8q/view?usp=sharing

Any help would be much appreciated!
Regards,
Gery

Posted : 28/12/2024 11:37 am
Gery S.
(@gery-s)
Member
Topic starter answered:
RE: Having trouble understanding z height steps

To specify my problem, here are the first 3 layers.

The third layer prints on the raft (which is at 0,3mm), at the height of 0,650mm.
So everything you see on layer 3 is printed "mid air" or in other words way too high!

To add more info. I'm using prusaslicer 2.8.1 on a snapmaker J1s.

Posted : 28/12/2024 12:03 pm
Neophyl
(@neophyl)
Illustrious Member
RE:

To attach files you need to zip them up first.  

If you are printing on supports or a raft (which is basically a support structure) then the layers above will be printing in mid air, as they are following the slice gap defined under raft/supports.  Unless you have a gap of zero defined.  Which is only valid if using soluble supports or ones of a dissimilar type so that they don't fuse with the part.

You have a 0.3mm first layer, followed by a raft gap of 0.15, and your first actual layer is at 0.65, which has a layer height of 0.2mm.  Math all seems to check out, 0.3+0.15+0.5=0.65.  So what's the problem with the slicer ?  It's doing exactly what you have configured it to do.

Ignore the layer heights of the support structures, they are confusing you are supports have always had a completely different and independent layer height to the printed parts which can make the slider seem confusing.  That's why they have heights that don't fall neatly into what you expect.

Posted : 29/12/2024 12:07 am
Gery S.
(@gery-s)
Member
Topic starter answered:
RE: Having trouble understanding z height steps

This whole raft being treated as support structure is a real let down.
Solid model parts on raft not being connected, how should this work? After some layers the whole thing comes loose and failed the print.
Sure i can set it to zero, but that would mean it's also zero with real supports and the model itself.
I think prusa slicer and the J1s doesn't work very well together. I think my journey with PS is over.

Posted : 29/12/2024 7:52 am
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