Question Square corner bulges + low PA corner gapping

[stevereno30]

I feel like I must be missing something in Super Slicer (update: I'm not. This is apparently related to my extruder producing corner gaps at much too low PA values around 0.026) that could help prevent this issue:


Three prints are visible in this image. 20 more are in the background, almost all with this issue. I've tried everything: lowering acceleration, lowering speed, lowering square corner velocity to zero... No matter what I do, the corners have this overshoot artefact. The only way I have been able to get rid of this is to double my pressure advance (from 0.02 up to 0.04). The problem with this is that it causes dramatic corner perimeter gaps. Prusa Slicer does a bit better job (despite having higher speeds, accelerations, etc) but I still can't get these to go away. The bottom of the stack of test prints was printed with 40mm/s perimeters and roughly 20mm/s external perimeters. It also had square corner velocity set to zero. The other two were 5 and 10 square corner velocity, and both had print speeds significantly higher, but the improvements are negligible considering how terribly slow the machine was running. The bulging is only on the trailing side of the corner, so I don't think it is PA induced bulging. Any suggestions would be greatly appreciated!

 

[claudermilk]

Have you gone through the Ellis Tuning Guide? According to his troubleshooting tips pressure advance is too low.

 

[stevereno30]

Have you gone through the Ellis Tuning Guide? According to his troubleshooting tips pressure advance is too low.

This would be true if the bulge happened on both sides of the corner, but it only happens on the trailing side. If I tune PA higher, corner gaps appear which indicate that PA is too high.

 

[Defib]

PA should be between 0.04 and 0.06 on cw1 or 2 running abs. Is the corner pictured the corner where the seam is going down? Square corner velocity 5 should be a safe value to use. Also give this a try for tuning it in: https://ellis3dp.com/Pressure_Linear_Advance_Tool/

 

[stevereno30]

PA should be between 0.04 and 0.06 on cw1 or 2 running abs. Is the corner pictured the corner where the seam is going down? Square corner velocity 5 should be a safe value to use. Also give this a try for tuning it in: https://ellis3dp.com/Pressure_Linear_Advance_Tool/

None of corners shown above were seam corners. I never knew there was an acceptable range of PA values with my extruder/matieral... the old lines method would give best-case results with a PA of 0.035, but Ellis' new corner tool made me drop that down to 0.02. Any higher, and gapping appears, but that value is a long way from eliminating bulging. Since I get corner gapping with such low PA values, would that be indicative of extruder issues? I'm unsure where to begin on correcting that.

 

[NoGuru]

I would try a different slicer to see how it affects the print.

Is this on all corners?

 

[stevereno30]

Every once in a while I will give Cura or Prusa Slicer a go, but I'll always end up back with SS. However, I will give them a shot again. That being said, I'm doing a minor rebuild at the moment. I think my clockwork drive gear was self-aligning in a way that made the plastic gear mesh only with the outermost edge of the motor 10t gear (In other words, the BMG gear was butted up against the plastic gear like the CW1 guide directs which caused the filament to pull the clockwork gear assembly toward the front of the extruder). I have no idea if this is what has been causing issues, but in the process of disassembly, I stripped out the drive gear grub screw, so I'm waiting on a high quality 1.5mm hex driver to (hopefully) get that grub screw out. I'm also deracking and replacing A/B belts. Frustratingly, if I solve my print issue, I will have changed too many variables to be confident of the root cause 😂

 

[Oberon]

Do we agree that all corners have this issue even though it's only on the trailing edge ? Just to rule out any mechanical issue that would be axis specific.

It's puzzling that with PA values like that you get bulging. 0.02 is low and personally my ABS/ASA profiles hover around 0.035-0.045.

Just a few wild guesses since no one else seems to have better ideas :

Do you have input shaping enabled and what are the values ? Do you still have the graph that the script outputs ? Just thinking if you might have a typo / misconfigured input shaper.

If it's a hardware issue / defect it doesn't look like something common or intuitive so your most likely strategy is to chase anything that's related to the extruder that doesn't look perfect.

 

[stevereno30]

Yes, all four corners had the issue, but only on the trailing edge. The bulges remain if I print at a 45 degree angle. I feel it has to be mechanical, so I'm chasing that at the moment. Based on Dfib's comment as well as yours, my assumption is that I will eventually need a much higher relative PA.

As for the wild guesses, I do have input shaping on. Currently x is set to 3 hump @ 88hz, and y is set to ei @ 47hz. I know they aren't entered with typos because I configure input shaper using the automatic calibration (shaper_calibrate).

Also, lower PA values typically result in bulging. The surprising bit is that I get corner gapping at such low PAs.

 

[stevereno30]

With my rebuild done, this is my PA test with my extruder set to over extrude by 1%. Effectively the same result. What I would consider significant gapping appears at 0.026. Bulging seems to be gone at 0.032. I'm lost. Also, correct me if I'm wrong, but since this issue appears in Ellis' PA tool, that rules out the issue being Slicer-related.

 

[stevereno30]

With my rebuild done, this is my PA test with my extruder set to over extrude by 1%. Effectively the same result. What I would consider significant gapping appears at 0.026. Bulging seems to be gone at 0.032. I'm lost. View attachment 1372

Here are some extra bits of information that add to my mind-breaking problem: PA is just as low with CW1 as well as with an orbiter style extruder. I've tried a CHT nozzle, standard and high flow dragon cores, and different print temps. The only extruder-related parts I've not swapped at this point are the stepper driver, the wiring harness, and the MCU. Can anyone think of a way that any of those could contribute to my low PA values?

 

[m00dawg]

I can't say I'm an expert here but that feels like perhaps something off with your esteps or extrusion multiplier

 

[stevereno30]

I can't say I'm an expert here but that feels like perhaps something off with your esteps or extrusion multiplier

I wish it were that simple... My rotation_distance is 23.1 and my extrusion multiplier is 0.93. Both of these are well within the range of "normal." Also, the extruder gives 100mm if asked for 100mm. I calibrate hot, so that is 100mm extruded through the hotend, not just through the extruder.

Also, as an update, swapping motor slots/drivers on the MCU made no difference. The machine is still producing perimeter gaps when PA ≥ 0.026.

 

[m00dawg]

Yep those are in the ballpark of my settings. On my 2.4 rotation_distance ended up being best at the LDO default (22.6789511) and my EM is 0.90 with a PA of 0.04 (EM/PA are the same for PLA and ABS though I haven't tested PETG yet). I'm using a Rapido (standard flow). 0.90 is probably underextruding slightly so I think the sweet spot is somewhere between 0.90 and 0.95. That's with Atomic Filament. On my V0 PA is 0.03 as I recall (with a Dragon BMO) (with the same filament). In your above test, I would have picked .034 to try.

I don't think it's this but just for fishing for options, have you done the belt pitch tests or otherwise have checked to make sure you're not skipping? I definitely had to re-tighten after the break. That was causing layer shifting though and not overshooting on corners.

The above probably isn't of much help :/ but at least you have numbers to maybe compare to (though it's apples to oranges).

 

[stevereno30]

Yep those are in the ballpark of my settings. On my 2.4 rotation_distance ended up being best at the LDO default (22.6789511) and my EM is 0.90 with a PA of 0.04 (EM/PA are the same for PLA and ABS though I haven't tested PETG yet). I'm using a Rapido (standard flow). 0.90 is probably underextruding slightly so I think the sweet spot is somewhere between 0.90 and 0.95. That's with Atomic Filament. On my V0 PA is 0.03 as I recall (with a Dragon BMO) (with the same filament). In your above test, I would have picked .034 to try.

I don't think it's this but just for fishing for options, have you done the belt pitch tests or otherwise have checked to make sure you're not skipping? I definitely had to re-tighten after the break. That was causing layer shifting though and not overshooting on corners.

The above probably isn't of much help :/ but at least you have numbers to maybe compare to (though it's apples to oranges).

With brand-new belts, you're right. I will have to re-tighten before long. I have done slight adjustments to tension (like 1/4 turn on my idlers) but nothing beyond that yet. That being said, the new belts had to perceptible impact on anything other than my shaper values.

0.034 on the test above definitely is the best choice for bulging, but the gaps are pretty awful at that value. The photo doesn't show gaps all that well, but they are significantly worse than this:

 

[JendaDH]

I have the same issue I'd say. Fresh built v2.4.

I have clear gap in perimeters when there is sharp turn. I tried to play with PA from 0.038 to 0.052. The later is what the Ellis guide points me to.
My nozzle is 0.4, extrusion width is also 0.4 here are the details:


My EM is around 93% to 95%. If I go bigger, the top surface is over extruded. My Hotend is Phaetus Dragon UHF.
Material is Prusament ASA printed at 265 degrees.

These are my printing speeds, same was visible when the outer perimetr was in the rage of 40-50mm/s


Here is the detail of the gap:
Nema 17 Mount on Micron -> gap_1
Voron 2.4 skirt -> gap_2

Currently my PCF is set at 60%, not sure if that is too much or not. I might experiment with this setting too,

 

[JendaDH]

Just for the record here, I managed to resolve the gap in perimeter by tuning PA and smooth timing.

 

[stevereno30]

Just for the record here, I managed to resolve the gap in perimeter by tuning PA and smooth timing.

Good to know! I fixed mine by adjusting overlap settings instead of EM. I'm printing with my EM set to 1.0 and instead tuned my to surfaces by setting overlap somewhere in the 30s for solid infill and in the 70s for perimeters.

 

[JendaDH]

Good to know! I fixed mine by adjusting overlap settings instead of EM. I'm printing with my EM set to 1.0 and instead tuned my to surfaces by setting overlap somewhere in the 30s for solid infill and in the 70s for perimeters.

Interesting, will look into that too. I have my infill at 30% for solid. Will look at the perimeter, might be better option to get nice corners without bulging.