Problem with Curling on Overhanging Fillets/Chamfers Causing Blobs on Transition

[AlbatrossFPV]

I've been having this specific problem for nearly as long as I've been using this printer. The issue is that when I try to print an overhanging fillet or chamfer (such as the test part pictured), the overhanging bit of the layer seems to curl up and continues doing this until the print reaches the straight, non-overhanging section of the print, when it seems to condense all of the curling into one glob (visible as the giant glob that runs along where the transition between overhanging and straight walls)

This happens equally along the entire outside edge of the print, seemingly no matter the size of the print (pictured test object is 40x40mm, but I have also tried 130x70mm with the same issue). The test part also has 2mm thick walls, in case that is good to know.

The printer I am using is a Voron 2.4 with Afterburner and a Phaetus Dragon hotend. I'm printing in Spool3D PLA and a 0.4mm nozzle. The model was sliced using PrusaSlicer 2.8.0. Some things I have tried, with next to no success are:

• Reducing print temperature (215C -> 190C)
• Increasing fan speed (50% -> 100%)
• Reducing speed (110mm/s -> 50mm/s)
• Increasing perimeter extrusion width (0.44mm -> 0.6mm)

Some of my print settings are outlined below:

• 0.2mm layers
• 3 perimeters
• 3 bottom layers, 4 top layers
• 20% gyroid infill
• No supports
• 50mm/s perimeter speed
• 60-70mm/s infill/solid infill speeds
• 0.5mm perimeter extrusion width
• 0.56mm external perimeter extrusion width
• 0.44mm extrusion width for all other features

Some of my filament settings are outlined below:

• Spool3D PLA
• 0.93 extrusion multiplier
• 200C first layer
• 190C other layers
• 60C bed
• 100% fan

Also worth noting is I've had this problem with 3D Printing Canada ABS as well when trying to print the Voron 2.4 panel clips, and was only able to get rid of it by decreasing the extrusion multiplier way below what I was comfortable with, leading to the perimeters actually being separate structures and not sticking together. There was still even a small bulge after doing this, it just wasn't an uneven and gloppy bulge at least.

If any more information would be helpful, feel free to let me know. Thank you in advance for your help

 

[NoGuru]

If you are using Afterburner, my guess would be not enough cooling. Think about upgrading to SteathBurner or something with more air flow.

 

[AlbatrossFPV]

I am planning on upgrading to the Stealthburner shortly, however, I'm not sure it'll solve all of my problems. To try to rule out cooling as an issue I printed another test object with a large tower fan pointed into the printer chamber,. running full blast the entire time. In spite of this, the test part didn't look any better and maybe even looked worse. (done with the printer settings mentioned above)

 

[lord-carlos]

What is the actual speed of those of those outer overhang perimeters?
I would also suspect cooling.

In Prusa Slicer there is a setting to slow down for overhangs, depending on how steep they are. Some other slicers have a bug where overhangs are getting printed at over bridge speed. So looking at the "print speed view" can help.

My steathburner is also radically bad at overhangs.

 

[AlbatrossFPV]

The actual speed of the overhanging (external) perimeters seems to be 30mm/s, which is what I set it to.

The weird thing that I have noticed is that it only seems to be a problem with these think walled parts, since all of my other overhangs turn out nearly perfectly, even beyond 75%. When I printed a benchy and a temperature tower a while ago, there were no noticeable defects. I'm going to print the same test object, just not hollow later today to see if the thin walls are indeed the culprit.

 

[NoGuru]

It REALY looks like cooling even if you pointed a fan at it.
The other thing could be over extruding. Try setting perimeters first in the slicer.

 

[AlbatrossFPV]

Try setting perimeters first in the slicer.

I've already got perimeters set to print first in the slicer, I'm pretty sure that's the default in PrusaSlicer (at least for the profile that I based mine off of)

The other thing could be over extruding.

I'm disinclined to think this, since I tuned the extrusion multiplier to within a percent using Ellis' tuning guide and my top layer does look quite good. It could still be influencing it a bit though, compounding with other factors.

It does certainly seem like a cooling issue, so I suppose I'll just have to see if switching to the Stealthburner will help at all.

 

[NoGuru]

Sounds good. One last thing is to try another slicer. Orca is very good out of the box. I mean just to see if it has any influence.

 

[AlbatrossFPV]

One last thing is to try another slicer

Yeah, that might be worth trying actually. I don't know why I never considered that

 

[lord-carlos]

In Prusa Slicer you can set the overhang speed to dynamic. Higher overhang = slower speed. You could also try that. It will not change the "normal" perimeter speed.

 

[NoGuru]

I used to bounce from slicer to slicer but I am finding Orca so good I pretty much just use that now unless I see some weird artifacts in a print.

 

[claudermilk]

Orca also allows the dynamic overhang speeds. Like @NoGuru, I was bouncing between slicers (SuperSlicer & Orca) but have gotten comfortable enough in Orca that it's my go-to now. Both Orca & SS offer enough additions that I use that I haven't been back to Prusa for a long time.

 

[AlbatrossFPV]

That's good to know. I think I mostly stuck with PrusaSlicer because I wasn't familiar with the interfaces of any other slicer, but that's easily solvable
I'll definitely try out Orca soon!