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Question about bed leveling, nozzle size, layer size, and the slicer...


tundrwd
(@tundrwd)
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Ok, question here. 

Ok, I’ve leveled my bed using paper, and I’m going to use a 0.4mm nozzle on the hot end.  The slicer is set to output 0.2mm layers.  The slicer (Cura), has been informed that I’m using that 0.4mm nozzle, and the physical characteristics of the 3D printer.

So the question is - does the slicer “understand” that it needs to raise the hot end 0.2mm off the printer bed, and for each successive layer?

The reason I’m asking is - how sensitive is the initial height of the hot end nozzle off the bed.  So, if I somehow set the height through leveling the bed to ONLY that 0.2mm height - that’s going to make the layer smear on the bed..  So -  just how much does the initial height need to be so it doesn’t drag through the layer just deposited - or does the slicer create G-code that accounts for that?


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Wurlitzerwilly
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If you select Standard Quality - 0.2mm, Cura will always produce Gcode to produce 0.2mm layers, but you can change the 1st layer to something else if you want.
The usual way to set the 1st layer height is to level the bed with paper, then run a 1st layer test, which you can adjust on the fly by changing the nozzle/bed gap.
I prefer to 'level' the bed using paper, so that the gap is consistent over all the bed (if possible) then use the Z-offset to set the actual gap I want for a good 1st layer.

Here's a calibration link with a Gcode generator to set 1st layer correctly:

https://teachingtechyt.github.io/calibration.html#firstlayer


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tundrwd
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@wurlitzerwilly  That's not really what I'm asking - assuming the bed is properly leveled, and what I've been printing for days is all at the layer height of 0.2mm and the results are "perfect"...

Now - I want to change the layer height to 0.3mm or even more, say 0.5mm - does that affect my initial bed leveling - or does the slicer (Cura) account for that so the new thicker layer doesn't drag through previous layers already set down on the bed?

Or - I want to change my layer height to 0.12mm - again does the slicer account for that difference so that the bed leveling I did that works for 0.2mm also works for 0.12mm?

Does that help?

I'm just curious if the slicer will account for changes made to the printer, printer selection, etc. as I change nozzle diameter (0.4mm say to 0.2mm nozzle), or layer height, or ....


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Wurlitzerwilly
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The slicer doesn't account for settings within the printer. It assumes that if it tells the printer to go to zero, that's where it will go, it then builds up from there. The slicer has no idea what your levelling gap is set to or what value your Z-offset is set to in Eeprom.
Cura will calculate a layer height in proportion to the nozzle size according to the quality you choose, so if you increase to .8mm and specify it in Cura settings, Cura will set a proportionally larger layer height. You can still change those heights by setting a custom profile.

You don't need to re-level if you change your nozzle size *except* that when you fit the new nozzle, if it's not at exactly the same height in the hot-end as the previous one, then your Z-offset (in the printer Eeprom) will need adjusting, but unless you disturb the bed or hot-end, over-all level should be correct.

The safest way to get it right is to print a 1st layer test for the new nozzle and baby-step the Z-offset for a good layer.

This post was modified 1 month ago 2 times by Wurlitzerwilly

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tundrwd
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@wurlitzerwilly Thanks!  that is what I was wanting to know.  


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