@Thomas_Sanladerer @Ryan_Carlyle @Jason_D After there was some dispute I made a quick test. Left printed with the real nozzle diameter and on the right same settings but a .05 mm (50µm) reduced nozzlediameter (including line width within cura) for me this looks like underextrusion, what do you think? (its a single wall print, on dual wall prints this doesn’t look so bad)
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You wont get a valid comparison if you modified the line/extrusion width in the g-code to be different. This will effect numerous parameters like the line positioning, etc.
Try 2 prints with completely identical settings other than nozzle diameter. Make sure you manually set the line/extrusion widths (the same for both test pieces) in the settings as some slicers’ default settings calculate line width as a function of the nozzle diameter and layer height. As long as you are printing at a conservative speed so nozzle pressure doesn’t cause missed steps or filament grinding, your prints will be identical.
that is what i did, i manualy set the linewidth smaller(outer wall , inner wall and wall thickness )- and i was wondering how well that works for multiwalled objects, but not on singlewalled/spiral prints.
Why would you set it smaller if you are trying to compare the effect that the nozzle orifice setting has on the print?
By setting the line width narrower, the slicer will reduce the amount of plastic it attempts to push through the nozzle
In addition if you set the line width smaller than the actual nozzle diameter you will get poor “squish” on the extrusion and it will look worse. Extrusion width should almost always be set wider than the actual orifice diameter, and preferably atleast 150% of the layer height aetting
@Jason_D here with a bigger extrusion width - i still think they are not looking the same.
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@Jonathan_Knirsch That is because you are thinking about what you observe when a nozzle is extruding into open air (where die swell also is a factor). When extruding against a surface and moving parallel to that surface, it doesn’t have the same effect. The slicer will call for a certain amount of material. The nozzle will extrude that material in a predefined volume. Assuming the motor doesn’t skip steps or lose grip on the filament from grinding against it, you will get the exact same end result.
It’s not about the length of the strand extruder in mid air. Its the volume of material extruded. And even if it were about the length of the strand… we have been talking about changing the nozzle diameter setting in software. not actually changing the nozzle out. So the volume the slicer would attempt to extrude would be the same, and the length would be the same if you used the same nozzle.
@Jonathan_Knirsch We have been talking about the volume of material. And the person you are agreeing with and telling is correct is talking about slicer settings too. Might want to re-read the conversation
@Jonathan_Knirsch when extruding the plastics while printing, the volume will not be the nozzle diameter but the linewidth×layerhigh×linelength. So the nozzle diameter didn’t play a direct role here but— and that is what i tried to explaine is that if the linewidth is not corresponding proper with the nozzle diameter (linewidth is bigger) then more plastic needs to be squeezed horizontally. You may only experience a difference when there is a big factor between nozzle∅ and layerhight. So for the normal user the nozzle diameter is unimportand aslong it is smaller than the linewidth (on multiwalled objects also smaller linewidth worke quite well as the minimized amount could be pressed against an existing wall)
Don’t forget about die swell! When you extrude in free air through a 0.4mm nozzle, the strand that comes out is about 0.6mm diameter…
There’s an old school of thought that says you should select layer height and extrusion width to have the same cross-sectional area as the noodle extruded in free air after die swell, but I’ve never heard a good rationale for why it would matter.
@Ryan_Carlyle when both areas are the same - the flowspeed of the fluid at the noozlediameter would be equal to the movement/extrusion speed. So if this match you probably would expect a minimum of turbulence and min shear stress. But when i calculate… i am running with 0.2 - so the speed within the nozzle is 5× slower … works for me so far. Values above 1 would mean a spill up of molten plastic (nozzle speed is faster so it will squeeze/slow down to get the volume extruded.)