Printing problems with 0.8 nozzle

[Corrado1 0]

Good evening.
I attach two profiles with which I printed the objects in the photos.
For both cases I used the cube with only one part to calculate the flow rate.
with the 0.4 nozzle the result is acceptable to me, especially the size is almost close to perfection: the external diameter of the cylinder should be 13mm and instead it turns out to be 12.8mm.
with the nozzle 0.8 and its profile things get worse both aesthetically and dimensally:
1) in correspondence with the layer change the material protrudes outwards leaving a hollow inside (unfortunately the photos are a bit blurry). frankly it's the first object I've printed with a "layer height of 0.4" but I don't think it's a defect linked to this
2) the most serious defect for me is the dimensional error: now the diameter is 12.6mm. Too much for my needs.
I also tried to set a flow rate to overextrude but the object is always undersized (furthermore it doesn't seem like the correct way to go even if the problem had been solved).
I could perhaps use "scaling factor shrinkage compensation" but even in this case I don't think it's the right way.
Could the print speed be too high for a 0.8mm nozzle? I don't think so since the flow test suggests I reduce the flow contribution.
Last clarification, I have never calibrated the e-steps because the topic is decidedly unclear to me.
I await your help.

EN3MAX_ Bolt Spacer 0.4 nozzle.3mf EN3MAX_ Bolt Spacer 0.8 nozle.3mf

[Slashee_the_Cow 274]

Howdy!

 

Slowing down the print would help: you're extruding about four times as much filament (by volume) than a 0.4mm nozzle. The hot end needs to be able to heat it all the way through as it flows through. Slowing down the print = lower flow rate = more time spent in hot end. You might also want to increase your print temperature a bit to compensate.

 

2 hours ago, Corrado1 said:

I also tried to set a flow rate to overextrude but the object is always undersized (furthermore it doesn't seem like the correct way to go even if the problem had been solved).

2 hours ago, Corrado1 said:

I could perhaps use "scaling factor shrinkage compensation" but even in this case I don't think it's the right way.

Correct! It's not the right way. The right way is to change the setting Walls > Horizontal Expansion. Increasing the flow rate doesn't really guarantee "wider lines" either, especially on a print like this (where there are so few lines, and they're not constrained by walls).

 

2 hours ago, Corrado1 said:

in correspondence with the layer change the material protrudes outwards leaving a hollow inside (unfortunately the photos are a bit blurry). frankly it's the first object I've printed with a "layer height of 0.4" but I don't think it's a defect linked to this

I think I can see the problem in the photos. It is a bit related to the layer height though. Let's take a zoom in on the slice preview:

Okay, that's a bit more polygonal than real life, but put (hopefully) simply, the nozzle doesn't extrude the filament in this shape: └─┘

It extrudes it in this shape: O (since it's a round nozzle).

So essentially each layer is a little donut rather than a little cylinder. Increasing the flow can help a little, since there's a little bit that can trickle down (also helped if you slow down the print).

It's also present if you use a 0.4mm nozzle to print 0.2mm layers, just a lot less noticeable because the gaps are smaller:

 

3 hours ago, Corrado1 said:

Last clarification, I have never calibrated the e-steps because the topic is decidedly unclear to me.

Don't feel so bad. I've never done it either. I'll just tag @GregValiant who gives a great explanation of stuff like this.