Help me dial this PETG in...

[WobblyHand]

Too much tension can cause ringing, but it mostly just a function of mass. The table is heavy so it tends to bounce at the end of it's travel, and in the prusas' case, the head isn't a lightweight either. There are ways to reduce that, but it's complicated. Look up "input shaping" you would need to confirm what firmware Prusa is using, but I'm pretty sure it's Marlin. I also mentioned pressure advance before, and for Marlin it's actually called "linear advance" That one can be done pretty easily and can help a lot with keep the extrusion width steady.

PrusaSlicer is based on Marlin 1.0. I searched config.ini and there is no "linear advance." During the Z calibration, I noticed the line thickness was not the uniform along the X axis. I found a discussion on Klipper and Input Shaper on the Prusa forum. Interesting, but at the moment over my head. Would require a bit more study. It only seems to be a single thread, so not enough to proceed from.

I don't see any parameters like this in PrusaSlicer. Is this basically related to accel and decel values, or what? Klipper shows how to instrument your printer which is pretty neat.

 

[John281]

I've been following along interested to see what the solution is but it looks like you're still working on it. I have a couple thoughts, but I'm by no means an expert. I have the same machine as you.
The little blobs of burnt material are caused by excess material getting stuck to the nozzle and overheating and then getting deposited on the part. Make sure the nozzle is really tight. I recommend changing the nozzle just in case. It's possible there is leakage between the hot-end and the nozzle. The buildup on the nozzle can also be from the nozzle accumulating the fine strings that PETG tends to create. That's tougher to avoid.
If you send me the .stl and .3mf files for this part, I'll run it on my machine using Prusament PETG and see if I get the same result. If no problems, then I can send you my slicer settings and maybe you can figure out what is going on. Let me know if you want to give it a try.

 

[great white]

My printer uses a modified version of Marlin and My slicer is Cura, so I'm not going to be much good with specifics.

Settings are important, but more so understanding what they do. I've had to tweak settings even when just swapping from one spool to another, same manufacturer, same type/color of filament.

Unfortunately, the only cure for figuring out what does what is time, research and practice.....

Patience is implied. LOL!

 

[WobblyHand]

I've been following along interested to see what the solution is but it looks like you're still working on it. I have a couple thoughts, but I'm by no means an expert. I have the same machine as you.
The little blobs of burnt material are caused by excess material getting stuck to the nozzle and overheating and then getting deposited on the part. Make sure the nozzle is really tight. I recommend changing the nozzle just in case. It's possible there is leakage between the hot-end and the nozzle. The buildup on the nozzle can also be from the nozzle accumulating the fine strings that PETG tends to create. That's tougher to avoid.
If you send me the .stl and .3mf files for this part, I'll run it on my machine using Prusament PETG and see if I get the same result. If no problems, then I can send you my slicer settings and maybe you can figure out what is going on. Let me know if you want to give it a try.

I can do that! Give me a few minutes, maybe an hour to get all that ready. I just want to check that what I send you is really what was printed... After so many permutations, I need to make sure what my settings really are...

edit: saved the files, running a print now.

 

[MikeWi]

PrusaSlicer is based on Marlin 1.0. I searched config.ini and there is no "linear advance." During the Z calibration, I noticed the line thickness was not the uniform along the X axis. I found a discussion on Klipper and Input Shaper on the Prusa forum. Interesting, but at the moment over my head. Would require a bit more study. It only seems to be a single thread, so not enough to proceed from.

I don't see any parameters like this in PrusaSlicer. Is this basically related to accel and decel values, or what? Klipper shows how to instrument your printer which is pretty neat.

check this: https://marlinfw.org/docs/features/lin_advance.html
Klipper is fantastic, but I don't recommend it until you are comfortable working with what you have. Klipper is better, and easier to configure (no compiling) but it's also more technical. This kind of tuning isn't done in the slicer, so you won't see it there.

 

[WobblyHand]

check this: https://marlinfw.org/docs/features/lin_advance.html
Klipper is fantastic, but I don't recommend it until you are comfortable working with what you have. Klipper is better, and easier to configure (no compiling) but it's also more technical. This kind of tuning isn't done in the slicer, so you won't see it there.

Thanks for that. I don't see an equivalent in PrusaSlicer 2.5.0, or due to my lack of knowledge failing to recognize it. PrusaSlicer does support adding custom g-code, but it is unclear if the basic firmware on the printer will recognize the codes.

 

[WobblyHand]

@John281 check your PM. If you cannot extract the files from your PM, I will send them to your email address.

 

[WobblyHand]

check this: https://marlinfw.org/docs/features/lin_advance.html
Klipper is fantastic, but I don't recommend it until you are comfortable working with what you have. Klipper is better, and easier to configure (no compiling) but it's also more technical. This kind of tuning isn't done in the slicer, so you won't see it there.

Following your reference and going to github for the source code, I see in MK3/Firmware/Configuration_adv.h that LIN_ADVANCE is defined. The following values are set.

/**
 * Linear Pressure Control v1.5
 *
 * Assumption: advance [steps] = k * (delta velocity [steps/s])
 * K=0 means advance disabled.
 *
 * NOTE: K values for LIN_ADVANCE 1.5 differs from earlier versions!
 *
 * Set K around 0.22 for 3mm PLA Direct Drive with ~6.5cm between the drive gear and heatbreak.
 * Larger K values will be needed for flexible filament and greater distances.
 * If this algorithm produces a higher speed offset than the extruder can handle (compared to E jerk)
 * print acceleration will be reduced during the affected moves to keep within the limit.
 *
 * See http://marlinfw.org/docs/features/lin_advance.html for full instructions.
 * Mention @Sebastianv650 on GitHub to alert the author of any issues.
 */
#define LIN_ADVANCE

#ifdef LIN_ADVANCE
  #define LA_K_DEF    0        // Default K factor (Unit: mm compression per 1mm/s extruder speed)
  #define LA_K_MAX    10       // Maximum acceptable K factor (exclusive, see notes in planner.cpp:plan_buffer_line)
  #define LA_LA10_MIN LA_K_MAX // Lin. Advance 1.0 threshold value (inclusive)
  //#define LA_FLOWADJ         // Adjust LA along with flow/M221 for uniform width
  //#define LA_NOCOMPAT        // Disable Linear Advance 1.0 compatibility
  //#define LA_LIVE_K          // Allow adjusting K in the Tune menu
  //#define LA_DEBUG           // If enabled, this will generate debug information output over USB.
  //#define LA_DEBUG_LOGIC     // @wavexx: setup logic channels for isr debugging
#endif

This leads me to believe that adding the g code to the beginning and end of the g-code file might work.
As is the K factor is limited to 10. Could add M900 K5 to the gcode and see what happens... I guess I'd put M900 K0 at the end.

edit: no idea if the defines are intended to be integer values or not.

 

[WobblyHand]

Not sure how to read this, but there already is M900 Kx code in the start g-code. Here it is. What is this doing?

M900 K{if printer_notes=~/.*PRINTER_MODEL_MINI.*/ and nozzle_diameter[0]==0.6}0.12{elsif printer_notes=~/.*PRINTER_MODEL_MINI.*/ and nozzle_diameter[0]==0.8}0.06{elsif printer_notes=~/.*PRINTER_MODEL_MINI.*/}0.2{elsif nozzle_diameter[0]==0.8}0.02{elsif nozzle_diameter[0]==0.6}0.04{else}0.08{endif} ; Filament gcode LA 1.5
{if printer_notes=~/.*PRINTER_MODEL_MINI.*/};{elsif printer_notes=~/.*PRINTER_HAS_BOWDEN.*/}M900 K200{elsif nozzle_diameter[0]==0.6}M900 K24{elsif nozzle_diameter[0]==0.8};{else}M900 K45{endif} ; Filament gcode LA 1.0

Since I have an MK3S+ and not a mini, then K=? I don't find that very readable code.

 

[MikeWi]

Following your reference and going to github for the source code, I see in MK3/Firmware/Configuration_adv.h that LIN_ADVANCE is defined. The following values are set.

/**
 * Linear Pressure Control v1.5
[/QUOTE]

...

Follow the directions in that link. You have to run their test print to figure out what those K numbers are. Then you can add them to your slicer's starting Gcode as shown instead of recompiling Marlin, which is a nuisance to be sure. You can't just enable it as without numbers specific to your printer, it's just going to make things worse.