Cura settings to fix problems with extrusion(?)

[sebhoff 1]

I recently changed my nozzle to 0.6mm (because I need to print some special filament) and since then, I have been having trouble with printing. Because I have next to no experience, I don't really know where to start fixing things. It doesn't seem to be z-offset (which, I think, I have calibrated reasonably well - although clearly not perfectly). I also did PID autotuning and double-checked flow (which is at a relatively low 85%) with one-wall test-cubes. The bed is clean (cleaned with isopropyl). Changing the first layer temp to 218 (as suggested in a Facebook group) didn't help, either. My hunch is that it has to do with retraction/extrusion settings, but I don't know. The attached 3mf is for a first layer calibration print, but I'm also having related problems at higher levels (stringing and problems at the seams). 

I'd greatly appreciate some hints about where I should go hunting down the problem. It's probably something obvious to you experts - but I'm struggling.

Sebastian

 

first_layer_0.6mm_nozzle_2.3mf

[Cuq 205]

Under Extrusion ...  

It's not really usual in the configuration to set the Flow to 85%.  Most of the time a Flow between 98 and 102% is logical as it should be a small adjustement. If you set your flow to 85% it's because you have follow the wrong Tuto on YouTube for the calibration of your E-Step and/or you are using just one Wall on your Cube to calibrate the Flow. But as Cura is not based on the Slic3r familly to get the right value you must use 3 or 4 walls to get an accurate result.

 

And Nozzle size even if it's not necessary it's better to set the Nozzle Size parameter to the right value: 0.6

Edited March 13, 2023 by Cuq

[ksihota 2]

Ensure that you have changed the extruder size in the Machine Settings and not just the line width etc. in the profile settings. I believe that is the suggestion in Cuq's response above but often people overlook this in their haste to get printing again.

When you switch to a larger nozzle you may need to up your temps a bit to take into account the extra flow from your hot end (more material needs more heat to melt.) It does appear that you may be under extruding a bit.

[sebhoff 1]

Thanks to both - very helpful! Will check and report back if I see any improvements!

Sebastian

[sebhoff 1]

OK - a little better, but not really. I've now set things to 100% flow (although calculations based on a test-cube with 4 walls of 0.6mm line width suggest it might have to be a little lower than that). Because I was playing around (and because that's what I saw in someone's settings), I also changed first layer height to 0.28mm. 

But I'm still seeing these odd under-extrusion/non-adhesion issues after travel movements. I can reduce them quite significantly by printing at 50% of the speed. But if I do the same with some more detailed prints, things still are too messy for my taste. Plus, it takes ages to print...

Anyway - am currently too frustrated to go on. Tomorrow is another day... 😆

 

[Cuq 205]

Level your bed, if you have change the Nozzle the distance nozzle / bed have change.

[sebhoff 1]

Thanks. But that's naturally the first thing I did. And I double-checked that the mesh is being used when printing. 

[sebhoff 1]

Just to confirm the levelling, I printed a massive 15x15cm first layer, and it came out reasonably nicely - apart from the very first cm when the beginning of the wall was printed. So I'm confident it's not the levelling/tramming, it must have something to do with flow/retraction/adhesion/temperature/whatever... 🙃

(The little bump towards the lower left corner happened when the filament got stuck a little and I had to manually intervene to get the filament to unroll again...)

 

[ksihota 2]

Have you checked the humidity of your filament lately. A little moisture might be causing some flow inconsistencies. How about the shape your nozzle is in?

Just grasping at straws here.
From the photos it appears to be those edge pieces. Do you have coasting turned on or another feature that might decrease flow as it reached the end of a path or corner so that there is a limited flow as it begins a new path?

[sebhoff 1]

Thanks for your input!

The filament is new and the house is very dry (too dry, actually).  And the nozzle is brand-new, too - it's a tungsten carbide nozzle (because I'm planning to print quite a bit of highly abrasive, food-safe filament).

One thing I'm not entirely sure about is whether I applied the correct torque when adding the new nozzle. But I'm pretty sure it is tight enough - just mentioning it as I'm also grasping at straws... 😉

I'm attaching the project I used to print this. Perhaps you can find something I have overlooked? (BTW, I did *not* manage to set the nozzle size in the printer settings, as suggested by Cuq, because there's no such setting in the "Machine settings" - but I did set this in the drop-down menu below "Preview".)

Large_first_layer3.3mf

[Cuq 205]

As you have change via the menu the nozzle diameter is now correct in the "Printer Settings".

Edited March 14, 2023 by Cuq

[ksihota 2]

LOL I don't have printer settings in my side menu. Guess I should add that.

 

This is the setting that sometimes gets overlooked. Not sure if it is critical but I am pretty sure I have had under extrusion issues when I forgot to change it.

[Cuq 205]

In 4.X Nozzle Diameter had a very small influence on the final result. With the  version 5.X there are a few more parameters that depend on this value. See another post :

 

 

To get the Printer Settings you need to Install the Printer settings Plugin.

[ksihota 2]

Does it appear to be a print speed issue where the filament is being pulled away from the bed before it has a chance to stick properly? Is it only on your first layer?

When I have had small objects (usually with PETG) that get stuck to the nozzle and pull off the bed, I usually set my first layer jerk to a very low setting and decrease my acceleration settings for the same. This usually allows those beads of filament to bond to the bed enough that the nozzle movement does not pull them free. I only need this for the first layer as after that the filament sticks to itself and can therefore run faster.

[sebhoff 1]

1 hour ago, ksihota said:

LOL I don't have printer settings in my side menu. Guess I should add that.

 

This is the setting that sometimes gets overlooked. Not sure if it is critical but I am pretty sure I have had under extrusion issues when I forgot to change it.

 

Mhm - I don't have "Nozzle size" in the preferences window...

 

[sebhoff 1]

56 minutes ago, ksihota said:

Does it appear to be a print speed issue where the filament is being pulled away from the bed before it has a chance to stick properly? Is it only on your first layer?

When I have had small objects (usually with PETG) that get stuck to the nozzle and pull off the bed, I usually set my first layer jerk to a very low setting and decrease my acceleration settings for the same. This usually allows those beads of filament to bond to the bed enough that the nozzle movement does not pull them free. I only need this for the first layer as after that the filament sticks to itself and can therefore run faster.

 

Yes, it does appear to be a general print speed issue. It is particularly noticeable on the first layer, of course, but it seems to apply in general. I printed something yesterday with snail-like speed for the first layer, and it turned out fairly OK. But it's still not as good as it used to be with much faster speeds when I still used the stock 0.4mm nozzle (using the exact same filament roll). 

Edited March 14, 2023 by sebhoff

[ksihota 2]

56 minutes ago, sebhoff said:

Yes, it does appear to be a general print speed issue. It is particularly noticeable on the first layer, of course, but it seems to apply in general. I printed something yesterday with snail-like speed for the first layer, and it turned out fairly OK. But it's still not as good as it used to be with much faster speeds when I still used the stock 0.4mm nozzle (using the exact same filament roll). 

I would try and figure out where the issue is actually happening in the first layer. On my prints with PETG it was when the nozzle quickly moved from point A to point B or tight corners. Because of that I was able to use the acceleration and jerk settings to slow those particular movements way down. I could adjust these specifically for the first layer as it wasn't a problem later on. It meant parts of my first layer was slower but the rest of the print could proceed as usual.
 

If you are printing PLA, have you tried increasing the 'squish' of your first layer just a little bit more to ensure that the adhesion was good on the first layer so the filament would not lift at all? That was not possible with PETG. I might also try increasing the first layer a little more just as a test. Maybe up to 0.3?

[sebhoff 1]

OK - many thanks for the pointer!

Using an extreme acceleration setting (reducing it from 500 to 100), things have now improved a lot! There's a slightly odd patch on the lowest square (in the position where there used to be a hole before), but that's a far cry from what it was before. Also, I'll obviously have to experiment a bit more when it comes to prints involving more than one layer, but at least there is light at the end of the tunnel! It's my birthday today - so this is a nice present. Thanks again!

 

 

[ksihota 2]

Happy Birthday🎂

You might also want to test out the jerk settings. I set some of the small items and sharp corners down to 5 or lower. those parts of the print slow down quite a bit but if its only on the first layer and you get better adhesion for those small pieces its worth it. Printing PETG on glass is sometimes really difficult to get the filament to stick to the bed rather than the nozzle.

I took a look at those tungsten carbide nozzles. Their printing characteristics (conductivity and hardness) look really good. I also noted that some have low friction coatings that make it more difficult for filament to stick to it.  I can't afford parts like that so I just use hardened steel for abrasive materials.

[sebhoff 1]

OK - now back from my holiday, and still struggling... 🤔 So I'm wondering whether I can use your generosity and knowledge a little more...

I've now started printing stuff with more layers (using a value of 100 for acceleration instead of the default 500), and while the results are OK-ish for some basic needs, it's clearly far from ideal. So I printed a test cube and here's the result...

As is quite obvious, one of the main problem now seems to be some sort of over-extrusion at corners: on the z-side of the cube, you can see that the corners bulge out. This was not the case before, from what I remember. Also, there are other things going wrong - I suppose this is called ghosting?

Before I use my two left hands to fiddle with the printer: am I right in assuming that this is likely an issue of hardware rather than Cura settings? So I'll have to go looking for problems with loose screws, tight belts and the like?

 

[GregValiant 1,305]

Any "ghosting" or "ringing" is typically where the nozzle changes direction.  I would expect to see some next to the X and Y as there is going to be at least a little bounce in the mechanicals.

The areas above and below the letters don't look so good either.  That part may be mechanical.

In the plan view of the top, it looks like you are over-extruding in the corners.  That might be because you are taking the corners too slow.  As a consequence there is a bit of oozing at each corner and that can cause what we see in that top view

For some reference...Accel is the setting for how fast the print head gets up to speed.  Think of Jerk as the minimum speed around a corner.  Try a test with the Accel at 1000 and the Jerk at 10 and see if it gets better.  You should be able to get those corner bumps down to about 10 to 25% of what we see there, but there is always a little bit as oozing can't be completely controlled without a lightning fast shutoff valve on the bottom of the nozzle.

If you have multiple problems (and you seem to have a couple) the symptoms can overlap.  Don't make too many changes at once and track your changes.

 

In regards to calibrating the flow - just calibrate the E-steps and then quit.  Everyone (and I do mean all people) who try to use some sort of "wall calibration cube" to further calibrate the flow ALL struggle with under-extrusion.  Whether it's Cura, or PrusaSlicer or another one, the math is very easy.  Trying to fill a 1 liter measure with 87% of a liter ain't gonna work.

Edited April 5, 2023 by GregValiant

[sebhoff 1]

Many thanks @GregValiant! Yes, I'm sure it's because I'm taking corners too slow - it only started when I reduced acceleration. The problem was that there was under-extrusion at the beginning of new layers or after the head had travelled some distance (see pics above). 

Will try with your suggested settings and report back. Thanks again!

[ksihota 2]

You can adjust your settings so the first layers are different than the rest. Often I will make sure my first layer has lower acceleration and jerk settings than the others to ensure that the first layer goes down nicely. The first layer can also be problematic if your filament is not sticking well to the bed nicely, so slowing it down gives you a better foundation for the rest where you can then speed things up.

[sebhoff 1]

Wonderful - @GregValiant, you are my hero...! 😊

It's not perfect, but certainly a lot better (left is new, right is old...). Thank you! The first three layers and the last three layers - so basically top and bottom - have a little more bulging than the other layers, but it's not as massive anymore as before. And X and Y are much more clear. The top layer is not smooth yet, but I haven't looked into optimising that...

Thanks, @ksihota - yes, I'm planning to have separate speeds/settings for the first and other layers. I haven't had any problems with adhesion at all, apart from the very first few mm after the head travels and extrusion starts again.  

[sebhoff 1]

OK - I've been trying to fiddle with the speed settings, but it seems to me that whatever I change, the speed of the walls (and infill) stays at a very slow 15mm/s - or something like that. Sorry - this may be very basic, but what am I missing?