RE: Nozzle cleaning consistently fails with PETG
interesting. I have no issues with PLA or PETG. Zero.
But as soon as I load anything other than those filaments, probing takes forever. The nozzle does multiple checks on one single spot. This is PA yesterday.
The good news is that, the probing does pass and the bed is level (it seems). It does seem unnecessary to probe multiple times on the same spot, which leads me to believe there is an issue with the cell and temperature in this design.
It is actually quite unsightly once the probing is done with PA. All these nozzle residue will end up in the bottom of a print too, causing other issues.
RE:
It does seem unnecessary to probe multiple times on the same spot, which leads me to believe there is an issue with the cell and temperature in this design.
I thought it is already well-understood that there is a hardware issue, namely the hotend heater current interfering with the Z sensing via the loadcell? Both are apparently sharing the same ground path from the main board to the Nextruder, which is a classic design no-no.
Disabling the heater during bed probing seems to avoid the probing issue, but leads to a significant, unwanted drop in nozzle temperature if larger areas with many probing spots need to be measured. Prusa could potentially provide a workaround in firmware by disabling the heater briefly, just for the Z probing -- then re-enabling it at full force while the Nextruder moves to the next location.
RE: Nozzle cleaning consistently fails with PETG
whatever they do, hope they do it soon. I like this printer but it needs a little more work.
This being my first prusa, and seeing how slow they are at integrating these fixes, makes me doubt of my choice sometimes. I do enjoy printing PETG and PLA but I boought this machine particularly to print the difficult stuff.
RE: Nozzle cleaning consistently fails with PETG
I gave up and went with an alternative nozzle cleaner from Thingiverse. No more nozzle cleaning failures, and the level probing works better as well. Still creates some small blobs with TPU but I can live with it.
RE: Nozzle cleaning consistently fails with PETG
Posted by: @raaz-2
Mhh, yes and no. While you can be able to clean it sufficiently, you really need have the contact surface of the nozzle against the bed completely clear of filament, otherwise the nozzle can leave little dots during probing and even make the probing inaccurate.
This doesn't happen to me. I get great prints. No dots—anywhere. In fact, it is when I used the old (original) code that I got little dots (irony). But aren't you saying that's the point? Those little dots on the front right side of the plate is Prusa cleaning the nozzle prior to probing?
I may try what you're suggesting, but right now I'm adhering to the "if it ain't broke, don't fix it" adage.
Although I may not sound like it—I am grateful for your responses! Thank you!
RE: Nozzle cleaning consistently fails with PETG
But aren't you saying that's the point? Those little dots on the front right side of the plate is Prusa cleaning the nozzle prior to probing?
Yep, the "nozzle cleaning" is just putting some dots at the front right corner while "probing a little area".
If you look at the Start G-code, it's doing a G29 P9 command at x=208 ; y=-2.5. There's no documentation (I can find) about P9, but G29 commands are all Bed Level commands. It's probably something special in the Prusa firmware, that does some "wipe movement" while lifting the nozzle.
G29 P9 X208 Y-2.5 W32 H4 (comment by me:) ; Nozzle Cleaning by probing a little rectangle
;
; MBL
;
M84 E ; turn off E motor
G29 P1 ; invalidate mbl & probe print area
G29 P1 X150 Y0 W100 H20 C ; probe near purge place
G29 P3.2 ; interpolate mbl probes
G29 P3.13 ; extrapolate mbl outside probe area
G29 A ; activate mbl
I may try what you're suggesting, but right now I'm adhering to the "if it ain't broke, don't fix it" adage.
Although I may not sound like it—I am grateful for your responses! Thank you!
Hehe I totally understand that!
For what it's worth, here's my current Start G-code, that definitely works. Did about 30 prints with it:
; 23nd June 2025 Start Gcode by Rasmus
M17 ; enable steppers
M862.1 P[nozzle_diameter] A{(filament_abrasive[0] ? 1 : 0)} F{(nozzle_high_flow[0] ? 1 : 0)} ; nozzle check
M862.3 P "COREONE" ; printer model check
M862.5 P2 ; g-code level check
M862.6 P"Input shaper" ; FW feature check
M115 U6.3.3+10442
M555 X{(min(print_bed_max[0], first_layer_print_min[0] + 32) - 32)} Y{(max(0, first_layer_print_min[1]) - 4)} W{((min(print_bed_max[0], max(first_layer_print_min[0] + 32, first_layer_print_max[0])))) - ((min(print_bed_max[0], first_layer_print_min[0] + 32) - 32))} H{((first_layer_print_max[1])) - ((max(0, first_layer_print_min[1]) - 4))}
G90 ; use absolute coordinates
M83 ; extruder relative mode
{if chamber_minimal_temperature[initial_tool]!=0}
M140 S115 ; set bed temp for chamber heating
{else}
M140 S[first_layer_bed_temperature] ; set bed temp
{endif}
M109 R{((filament_notes[0]=~/.*MBL160.*/) ? 160 : (filament_notes[0]=~/.*HT_MBL10.*/) ? (first_layer_temperature[0] - 10) : (filament_type[0] == "PC" or filament_type[0] == "PA") ? (first_layer_temperature[0] - 25) : (filament_type[0] == "FLEX") ? 210 : 170)} ; wait for temp
M84 E ; turn off E motor
;custom G-code start
M104 S0 ; turn off hotend heating for clean loadcell signals
;custom G-code end
G28 ; home all without mesh bed level
{if chamber_minimal_temperature[initial_tool]!=0}
; Min chamber temp section
; M104 S{idle_temperature[initial_tool]} ; set idle temp
G1 Z10 F720 ; set bed position
G1 X242 Y-9 F4800 ; set print head position
M191 S{chamber_minimal_temperature[initial_tool]} ; wait for minimal chamber temp
M141 S{chamber_temperature[initial_tool]} ; set nominal chamber temp
M107 ; Fan off
M140 S[first_layer_bed_temperature] ; set bed temp
{else}
M141 S{chamber_temperature[initial_tool]} ; set nominal chamber temp
{endif}
{if first_layer_bed_temperature[initial_tool]<=60}M106 S70{endif}
G0 Z40 F10000
M104 T{initial_tool} S{if is_nil(idle_temperature[initial_tool])}100{else}{idle_temperature[initial_tool]}{endif}
M190 R[first_layer_bed_temperature] ; wait for bed temp
M107 ; Fan off
G29 G ; absorb heat
M109 R{((filament_notes[0]=~/.*MBL160.*/) ? 160 : (filament_notes[0]=~/.*HT_MBL10.*/) ? (first_layer_temperature[0] - 10) : (filament_type[0] == "PC" or filament_type[0] == "PA") ? (first_layer_temperature[0] - 25) : (filament_type[0] == "FLEX") ? 210 : 170)} ; wait for MBL temp
M302 S160 ; lower cold extrusion limit to 160C
{if filament_type[initial_tool]=="FLEX"}
G1 E-4 F2400 ; retraction
{else}
G1 E-2 F2400 ; retraction
{endif}
M84 E ; turn off E motor
; custom G-code start
M104 S0 ; turn off hotend heating for clean loadcell signals
; custom G-code end
G29 P9 X208 Y-2.5 W32 H4 ; Nozzle Cleaning by probing a little rectangle
;
; MBL
;
M84 E ; turn off E motor
G29 P1 ; invalidate mbl & probe print area
G29 P1 X150 Y0 W100 H20 C ; probe near purge place
G29 P3.2 ; interpolate mbl probes
G29 P3.13 ; extrapolate mbl outside probe area
G29 A ; activate mbl
; prepare for purge
G0 X249 Y-2.5 Z15 F4800 ; move away and ready for the purge
M109 S{first_layer_temperature[0]}
G92 E0
M569 S0 E ; set spreadcycle mode for extruder
;
; Extrude purge line
;
G92 E0 ; reset extruder position
G1 E{(filament_type[0] == "FLEX" ? 4 : 2)} F2400 ; deretraction after the initial one
G0 E5 X235 Z0.2 F500 ; purge
G0 X225 E4 F500 ; purge
G0 X215 E4 F650 ; purge
G0 X205 E4 F800 ; purge
G0 X202 Z0.05 F8000 ; wipe, move close to the bed
G0 X199 Z0.2 F8000 ; wipe, move quickly away from the bed
G92 E0
;Set flow rate
M221 S100 ; set flow to 100%
RE: Nozzle cleaning consistently fails with PETG
I had similar problems, I moved the z stop to top of its slot from the bottom, re-calibrated unit, adjusted belts with spectrum analyzer where I found two peaks, fundamental adjusted to 85hz both belts, will show 170hz as well and this confuses Prusa's cell app. It needs a 24db filter with Q of 5 hz added to band reject 170hz. That would improve its accuracy and specificity. Other way was to take Tektronix MSO 2024 set chan 1 up to sinewave from a lab signal generator to 85hz, then use channel 2 with a microphone and trigger on channel 1. Then when you have synced belts to 85hz, you can superimpose channels and measure very precisely. MSO also has FFT math function running showing frequency spectra. Really what is needed is Prusa needs to setup a simple belt tensioner just like your car then its spring will always have correct tension on both belts. Cant believe they missed this simple thing.
RE: Nozzle cleaning consistently fails with PETG
interesting. how does that workaround look like? where can we find it in Thingiverse?
I gave up and went with an alternative nozzle cleaner from Thingiverse. No more nozzle cleaning failures, and the level probing works better as well. Still creates some small blobs with TPU but I can live with it.
RE: Nozzle cleaning consistently fails with PETG
My nozzle cleaning failures more or less when away when I swapped to Obxidian nozzle. It must be related to filament getting stuck on the tip of the stock brass nozzle.
Im loving the Obxidian nozzle, it virtually repels filament...I've cleaned it once in about 3 weeks , and that was due to an ASA print coming loose from the bed mid print.
RE: Nozzle cleaning consistently fails with PETG
there are several on Thingiverse. I like to simplify things so I made my own design. Will put it up on Thingiverse eventually. I can post the step file here if you like..
interesting. how does that workaround look like? where can we find it in Thingiverse?
I gave up and went with an alternative nozzle cleaner from Thingiverse. No more nozzle cleaning failures, and the level probing works better as well. Still creates some small blobs with TPU but I can live with it.
RE: Nozzle cleaning consistently fails with PETG
Anyone else still suffering from this extremely irritating issue?
I have alleviated it somewhat by readjusting the main cable and PTFE tube, but the problem still persists. I don't think it has anything to do with filament being stuck on the nozzle at all. I can completely clean my nozzle before starting a print, and make sure no filament oozes from the nozzle and I still get failures. I actually believe the entire problem is due to the poor design of mounting the main cable and filament tube. When the nozzle cleaning function is running, if I barely touch the main cable, even less than the tension from moving the extruder around the build plate, it will register as contact with the bed, stopping a few mm above it, before continuing to the next probe point.
I understand that disabling the nozzle heater allows it to pass by removing whatever interference it causes, adding to false load cell registers. However, that just seems like a band aid not an actual fix. Shouldn't the nozzle be heated during this procedure to make sure if there is filament that the nozzle can squish through it and still contact the bed?
RE:
I don't think it has anything to do with filament being stuck on the nozzle at all.
That's correct. When looking into the Start G-Code, the LCD shows "nozzle cleaning", while the command is just a modified bed level probing. (G29)
The nozzle is "cleaning", by doing a probe, followed by a horizontal travel and lift, repeating a few times.
Since the heater is messing with the loadcell, the probing fails, not the "cleaning".
About disabling the heater being an issue: you want the filament to be soft, but not printable. When cleaning the nozzle manually, there's a temperature range between 120-170°C, where most of the filament on the nozzle will be pulled off at once, when you grab it at a small spot.
During the nozzle cleaning, the temperature only drops from 170°C to around 140°C, so it still works completely fine.
The first "probing" squishes it without any real drop in temperature and the following moves just get rid of that squished part.
RE: Nozzle cleaning consistently fails with PETG
I don't think it has anything to do with filament being stuck on the nozzle at all.
That's correct. When looking into the Start G-Code, the LCD shows "nozzle cleaning", while the command is just a modified bed level probing. (G29)
The nozzle is "cleaning", by doing a probe, followed by a horizontal travel and lift, repeating a few times.
Since the heater is messing with the loadcell, the probing fails, not the "cleaning".
About disabling the heater being an issue: you want the filament to be soft, but not printable. When cleaning the nozzle manually, there's a temperature range between 120-170°C, where most of the filament on the nozzle will be pulled off at once, when you grab it at a small spot.
During the nozzle cleaning, the temperature only drops from 170°C to around 140°C, so it still works completely fine.
The first "probing" squishes it without any real drop in temperature and the following moves just get rid of that squished part.
I've heard mention of promised fixes for this issue in firmware but when checking the logs I don't see anything specific. I also dont see how firmware could actually fix it. Opening up the allowable range of loadcell registers would surely sacrifice performance elsewhere.
When comparing the cable mount with the MK4S, it's less than ideal. Between the cable strain, the electrical interference, and the raised letters in the "cleaning" area, we are left with unpredictable prints. I got tired of babysitting it so I flipped my sheet around for the time being.
I also get erratic bed leveling. Sometimes it will probe one point 5 or 6 times before moving onto the next.
Having experienced VFAs, Resonance issues, unpredictable "nozzle cleaning", failed z homing and bed leveling, I can't help but feel like the CORE One was rushed. It seems more like a mass produced prototype than a product thats designed for manufacture. Time will tell but I feel like we will get a bunch of firmware band aids for issues that require actual hardware to truly fix. I hope I'm wrong.
RE: Nozzle cleaning consistently fails with PETG
I also dont see how firmware could actually fix it.
I plan to look into it over the next two months. In theory, it's not really that complicated.
Whenever the G-code calls a G29 command:
The firmware simply needs to disable the heater before it starts the downwards Z-move to touch the bed and then switch the heater back on, as soon as the probing value is stored. Clean loadcell signals during the actual probing but barely any drop in temperature overall.
For the Homing, it just needs to disable the heater completely and switches it back on, when done.
I also get erratic bed leveling. Sometimes it will probe one point 5 or 6 times before moving onto the next.
Yep, same issue. The nozzle is moved down, the loadcell signal isn't "okay", so it probes again and again and against.
With the heater disabled, I get only 1 probe per point. Sometimes 2, when using the textured plate, due to the bigger deviations on the surface.
Having experienced VFAs, Resonance issues, unpredictable "nozzle cleaning", failed z homing and bed leveling, I can't help but feel like the CORE One was rushed. It seems more like a mass produced prototype than a product thats designed for manufacture. Time will tell but I feel like we will get a bunch of firmware band aids for issues that require actual hardware to truly fix. I hope I'm wrong.
100% agreed, yep.
I'm just happy that I'll be able to fix it with the community, since I like tinkering & testing and Prusa/Core One allow for that.
And the quality with the 0.25 mm nozzle, fuzzy skin and a Carbon-look-build-plate makes up a lot for the other issues:
RE: Nozzle cleaning consistently fails with PETG
With my new Core ONE, I had been printing some tests prints and small things with PLA and original PEI sheet. Then I changed the nozzle, switched to textured sheet, and tried to print PETG. "Nozzle cleaning failed" issues started, although the nozzle was perfectly clean. Retries lead to another issue: printer (falsely, I think) detected collisions and required homing, but also homing tended to fail. Basically, the printer became unusable, as the same thing happened also after restarts. I was only able to print with original smooth sheet and PLA, occasionally. Extremely annoying issue.
This thread was really helpful for solving it. Maybe not everyone has the same problem or root cause, but posts by Raaz and others saved my day: After disabling hotend heating before loadcell operations, everything has been working fine!
My assumption is that when I changed the nozzle and per instructions removed the hotend, I probably rearranged its cables a bit differently than originally when I built the kit. And now there is so much interference from hotend heater power cables that loadcell sensor values are not reliable? High current cables for motors or heaters and low-voltage sensors do not play well together when their cables are close to each other and not properly shielded.
Nevertheless, that simple change to printer's custom G-code solved my issue right away and it hasn't returned since. During probing, hotend temperature drops but the process goes through quickly as the values are now reliable and the printer doesn't need to repeat the test touches multiple times. I have not seen any effect to print quality.
Maybe I will try to rearrange or shield the cables later if I have time, but now I am printing happily again.
RE: Nozzle cleaning consistently fails with PETG
On my core one I edited the gcode
The physical nozzle cleaning maneuver is performed by this single line of code:
G-CodeG29 P9 X208 Y-2.5 W32 H4
This command instructs the printer to run a special probing pattern (P9) at the coordinates X208 Y-2.5, which is where the physical nozzle brush is located on the printer.
Just comment it out (in prusa slicer under printers tab) - custom g code.
so add a ; before the G-CodeG29 P9 X208 Y-2.5 W32 H4
RE: Nozzle cleaning consistently fails with PETG
Sad to report that my nozzle cleaning failed issue did return. Going through Prusa's document about the topic, I readjusted the nozzle and that immediately solved the issue, or so I thought. Maybe there was a gap and I managed to push the nozzle where it was supposed to be, as load cell sensor values clearly changed.
But then later the issue returned again. I tried Peter Farell's suggestion of commenting out nozzle cleaning routine. As a result, sheet probing reported that it looks to be misaligned. I declined recalibrating it (as there is nothing wrong with it, just again bad load cell values) and printed anyway. The print failed after a few layers, Z values where clearly off and the "always perfect first layer" was just terrible.
I am really confused about this. My printer seems to have troubles with incorrect load cell values, there is no point in trying to clean the nozzle or things like that. The printer might work for hours and multiple prints, then the next print I get nozzle cleaning failed and no matter what I do, it persists. I turn the printer off and come back next morning and it works just like that. Until again it doesn't. It is so random.
When I observe the load cell values while hotend is warming up (preheat) they seem to start from +100...+200 and go down to ~ -500 or so. If I tap the sensor, it shows even more negative value. Not sure what these readings are supposed to be, but at least I don't see anything random or weird.
What also puzzles me a lot is Prusa's logic *after* nozzle cleaning failed appears. It lowers the bed 10cm or so. If I then click retry, it starts probing from its current position, slightly moving up and down in a weird pattern, never gets up to hit the nozzle and before that always says "Crash detected", then tries to Auto-home, which again is those weird up-down pattern movements that never gets up to the nozzle, so then it says "Homing failed" and the only thing I can do is reset the printer. Then I try again, all the same things happen again. But sometimes it just might go through and print without any issues.
What an earth is going on? I don't care about nozzle cleaning, but since the load cell values also cause incorrect mesh bed leveling results and therefore ruin the first layer, I can't really skip it either.
I wish there was a possibility to continuosly observe the load cell values from somewhere. Maybe the sensor is bad? Or maybe some connection? Or maybe some high-current wire too close? Or maybe a bad cable? Who knows, but this is really difficult to debug.
RE: Nozzle cleaning consistently fails with PETG
Has this been resolved?
I am thinking of getting a second printer but not sure I can trust this one one yet? Have one thwt is working but don't want to risk getting a lemon. Already had one and it was returned and replaced due to these issues. Wondering what is the update about this.
RE: Nozzle cleaning consistently fails with PETG
Has this been resolved?
I am thinking of getting a second printer but not sure I can trust this one one yet? Have one thwt is working but don't want to risk getting a lemon. Already had one and it was returned and replaced due to these issues. Wondering what is the update about this.
Yes, this works for me now. I think the key is it that when you load new filament, after it flushed the nozzle with the new, it pushes some filament back.
RE: Nozzle cleaning consistently fails with PETG
What do you mean by 'it pushes some filament back'