Under-extrusion with 0.8mm nozzle for layer heights below 0.4mm

Hi everyone,
This is my first post on the RepRap forum

So, I have a Graber i3, with Marlin v1.1.9 in it and generally I use Slic3r for my slicing, using 1.75mm PLA filament, no bowden (everything is on the X carriage).

Recently I changed the default 0.4mm nozzle for a 0.8mm nozzle to experience with higher layer heights.
The problem I'm getting is that the minimum layer height I can get with this nozzle is 0.4mm, If I try something below that (even 0.35mm) I get severe under-extrusion, so severe that I can't even reach the first layer of the print because I can't get the skirt to be correctly extruded.
I can hear some very low pops on the hotend, and notice that at this low layer height configuration, the extruder motor turns very slowly (certainly pushing too little filament into the hotend).

Is there some sort of "minimum layer height" for a given nozzle size, is this probably a software misconfiguration, or a hardware limitation?

Thank you so much for any help!

Cheers!

Do you have the extrusion width set to a fixed value carried over from your old nozle?
Should be on Auto or something over 0.8 like 0.81.

I would suggest with a larger nozzle diameter that when your having problems only on the thinner layer heights that higher filament temperatures may allow filament flow. Print a temperature tower.

If this fails you may need a stronger extruder stepper motor.

I will be working with a 1mm nozzle here soon so I will learn to solve these problems first hand.

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Computer Programmer / Electronics Technician

Quote
MCcarman
Do you have the extrusion width set to a fixed value carried over from your old nozle?
Should be on Auto or something over 0.8 like 0.81.

hmmm gonna try play with extrusion width as well, but generally, I use de auto presets on Slic3r on the "print > advanced options". I attached a screenshot for that.

Quote
Roberts_Clif
I would suggest with a larger nozzle diameter that when your having problems only on the thinner layer heights that higher filament temperatures may allow filament flow. Print a temperature tower.

If this fails you may need a stronger extruder stepper motor.

I will be working with a 1mm nozzle here soon so I will learn to solve these problems first hand.

This is strange, because I can get a hell lot of extrusion with thicker layer heights, which makes questioning the strength of the motor ate least weird, if it can push a lot of filament, how couldn't it push small amounts?

Well, after trying all sorts of combinations with the advanced tab, I finally gave up and went to test with Cura.

Looks like Cura know how to slice low layer heights with big nozzles, so far I achieved good quality with 0.2 layer height with the 0.8mm nozzle.

I will try next to print something with 0.1mm layer height just out of curiosity. The thing is, it still prints large walls, so you can't gain any more resolution just playing with layer height, you need to step down on the nozzle too. But my plan here is just to minimize the layer visibility with this new setting

Edited 1 time(s). Last edit at 08/06/2019 12:51AM by lscarneiro.

Great!

When you get some good results would like to see your basic Cura's settings, this way I could get a jump start when changing to a 1mm nozzle.
Am also be curious about why Slic3r does not slice thinner layer heights that are working with your 3D Printer.

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Computer Programmer / Electronics Technician

Oh, I just used mostly of the default configuration in Cura, the only thing I changed was the speed, because my printer struggles with first layer adhesion in "high speed" (in my case, above 50mm/s), and then with stripped filament above 40mm/s so I changed it to 30mm/s to give a safe margin.

Important to mention that I only have those speed problems with the 0.8mm nozzle (probably because it needs to push a lot of filament to keep up with those speeds)