Nozzle cleaning consistently fails with PETG
I made a few test prints with PLA and they came off fine, however, when I switched to PETG for some structural parts I was getting constant nozzle cleaning errors when the print started.
These errors were on the textured sheet (which doesn't 'grip' the filament off the nozzle as well as the smooth ones during cleaning) and a small 'pancake' of filament would just stick to the tip of the nozzle during this process and it would fail. Even if I tried my best to clean the nozzle it still failed.
I finally managed to get a PETG print to start after making sure the inserted filament had stopped oozing and cleaning it thoroughly, but the next print I had the same issue. I'd have to babysit the printer to make sure not a single bit of filament was on the nozzle during the cleaning or it would fail.
My other printer is a MK4s with MMU3, which I never had issues with because the filament is only loaded when the print actually starts, so this may be an issue with the MK4s too, but this is the first time I'm experiencing this issue and its with the Core One.
RE: Nozzle cleaning consistently fails with PETG
Happens on the Mk4S also. No surprise as it's pretty much the same extruder. I just got used to picking pieces of filament off before bed mesh leveling starts. I miss the days of the Mk3S+ where I could just press print and walk away….
Formerly known on this forum as @fuchsr -- until all hell broke loose with the forum software...
RE: Nozzle cleaning consistently fails with PETG
PETG oozes, and moist PETG really oozes. There's just no way around it.
You have to clean your nozzle before you start printing. I preheat the printer, which only takes a few minutes for the nozzle to reach 170, then hit the nozzle with a brass brush and then start your print. Works for me every time without issue.
I don't have near the oozing I used to since running from my electronic dry cabinet. Some colors are worse then others, with white seemingly being the worst.
RE:
The problem here is that the print is failing in the nozzle cleaning part. I've had it sometimes where the nozzle does 20+ cleaning probes with no visible filament on the nozzle and still fails to clean. I feel like the cleaning tolerance is too tight and needs to be adjusted. Or the clean itself needs tweaking, as it only dabs the nozzle tip on the bed, perhaps a small movement just above the bed to try and drag any filament off? Not sure if it would damage the bed long term though
RE: Nozzle cleaning consistently fails with PETG
By cleaning the nozzle with a wire brush before starting the print I have never had a nozzle cleaning failure.
If there is leftover PETG on the nozzle the nozzle cleaning will fail. This is why I described the process in my previous post.
RE: Nozzle cleaning consistently fails with PETG
You could modify the retract lenght in the startcode for PETG the same as it is for FLEX
RE: Nozzle cleaning consistently fails with PETG
By cleaning the nozzle with a wire brush before starting the print I have never had a nozzle cleaning failure.
If there is leftover PETG on the nozzle the nozzle cleaning will fail. This is why I described the process in my previous post.
I understand that, however, I find it counter productive that a pre-print stage called nozzle cleaning fails because of filament on the nozzle, which is its entire purpose. Also, I don't really want to sit and baby sit my prints for the first 5-10 mins each time. I just feel like the cleaning stage needs to be modified to better clean the nozzle
Finally, with the currently know bug that opening the door during start and end of a print can cause a hard crash reset, its a little tricky to keep the nozzle clean when it heats to 170 and can start oozing as opening the door risks a crash (Core One issue).
RE: Nozzle cleaning consistently fails with PETG
By cleaning the nozzle with a wire brush before starting the print I have never had a nozzle cleaning failure.
If there is leftover PETG on the nozzle the nozzle cleaning will fail. This is why I described the process in my previous post.
I understand that, however, I find it counter productive that a pre-print stage called nozzle cleaning fails because of filament on the nozzle, which is its entire purpose. Also, I don't really want to sit and baby sit my prints for the first 5-10 mins each time. I just feel like the cleaning stage needs to be modified to better clean the nozzle
Finally, with the currently know bug that opening the door during start and end of a print can cause a hard crash reset, its a little tricky to keep the nozzle clean when it heats to 170 and can start oozing as opening the door risks a crash (Core One issue).
It only takes a few minutes, and if your going to probe the bed with the nozzle then it needs to be clean. I feel it's a material problem, not a printer problem. You already stated you didn't have the issue with PLA.
PETG oozes, there's no way around it, and it's worse if you didn't run from a drybox because PETG is hygroscopic.
It's a good idea to clean your print sheet with IA anyways before the print so what's another few minutes to clean the nozzle? The print is going to take hours.
You can just manually turn the nozzle to 170 and clean it if the preheat function is having issues currently.
Good luck.
RE: Nozzle cleaning consistently fails with PETG
Various other printers have nozzle cleaning stations -- silicone brushes or lips, or some other structure over which the nozzle is swiped across a few times before the start of a print.
Is there a retrofit solution which integrates well with the Prusa printers? Hardware-wise it should not take up too much of the addressable print space; software-wise the slicer and/or the printer should know about the blocked area, and the wiping should ideally be automatically performed before every print. Does such a solution exist for the Mk3/4 printers, or even adapted to the Core One already?
@brian-12 is right. Moist PETG oozes. If properly dried immediately before printing it doesn't ooze.
PETG asborbs moisture quickly, it's common for a long print to show signs of moisture near the end even when started perfectly dry. If you print sequential parts from the same spool without pausing to dry then it's normal for second and subsequent prints to show oozing problems at the start. If you are in the habit of starting prints remotely then unless you start immediately after loading fresh, dry filament you can expect problems, don't wait an hour or break for lunch if you want a problem free print.
Frankly, Prusa should never have made it possible to *start* a print remotely.
Filament with inclusions or large percentages of pigment are generally the most susceptible, pale and pastel colours are usually the worst.
Dry boxes do help but they don't prevent moisture absorption, they slow it down.
The larger the nozzle the greater the effect; I think this is why Prusa changed the standard XL nozzle from 0.6mm to 0.4mm, too many users were blaming the printer for errors which were really their own fault, if you are rigorous with drying the larger nozzles work as intended.
These errors were on the textured sheet (which doesn't 'grip' the filament off the nozzle
Some textured sheets don't start working properly until after they are first cleaned with dishwashing soap (Dawn/Fairy) and plenty of HOT water.
Cheerio,
RE: Nozzle cleaning consistently fails with PETG
Also, I don't really want to sit and baby sit my prints for the first 5-10 mins each time.
Tough.
It was usual with early RepRap machines to watch the first two or three layers in case of early fails. Prusa Mk2 reduced it to watching just the first layer and Mk3 just to watching all the first layer perimeters and the beginning of infill. With my XL I glance a few times at only the first two perimeters and then walk away. The Core One is of the same generation, I would expect to monitor the the first two perimeters.
A few minutes at the start when the whole print may take hours or even a few days is trivial.
Cheerio,
RE: Nozzle cleaning consistently fails with PETG
Since there's that extra 20 mm Y axis at the front of the machine I'm experimenting with a silicone "brush" (intended for a BL mini) attached to the front of a longer print sheet, and I have the gcode set to do quick scrub before the Prusa "nozzle cleaning". This type of thing has been done with the i3 series but there's extra room for it on the CORE so you won't lose any print area).
I had two nozzle cleans fail after PCCF prints due to a little bit of filament left on the nozzle, so I'm going to see if this prevents that.
Various other printers have nozzle cleaning stations -- silicone brushes or lips, or some other structure over which the nozzle is swiped across a few times before the start of a print.
Is there a retrofit solution which integrates well with the Prusa printers? Hardware-wise it should not take up too much of the addressable print space; software-wise the slicer and/or the printer should know about the blocked area, and the wiping should ideally be automatically performed before every print. Does such a solution exist for the Mk3/4 printers, or even adapted to the Core One already?
RE: Nozzle cleaning consistently fails with PETG
Let us know how your testing goes. I asked about nozzle wiper when the printer was first announced, and haven't heard anything about the topic until now. I have no trouble with the Mk4S nozzle cleaning procedure, and was able to solve the failed TPU nozzle cleanings by simply lowering the temp a bit, and haven't had a problem since. With the Core XY motion system, a cleaning pad of some sort seems like more of a possibility, and once I get my conversion kit I'll be interested in integrating something if it's a reasonable improvement.
-J
RE:
I can confirm that. Despite a completely clean nozzle, cleaning often fails. With the Mk4 there was a similar bug at the beginning where a value of the loadcell always delivered incorrect values and an overflow occurred which caused this. My MK4 before and XL also often got the nozzle cleaning successfully with filament at the tip. So I suspect that this is also a bug on the Core One FW.
A printer restart helped in my case. After that the cleaning was succesfully on first try.
I made a few test prints with PLA and they came off fine, however, when I switched to PETG for some structural parts I was getting constant nozzle cleaning errors when the print started.
These errors were on the textured sheet (which doesn't 'grip' the filament off the nozzle as well as the smooth ones during cleaning) and a small 'pancake' of filament would just stick to the tip of the nozzle during this process and it would fail. Even if I tried my best to clean the nozzle it still failed.
I finally managed to get a PETG print to start after making sure the inserted filament had stopped oozing and cleaning it thoroughly, but the next print I had the same issue. I'd have to babysit the printer to make sure not a single bit of filament was on the nozzle during the cleaning or it would fail.
My other printer is a MK4s with MMU3, which I never had issues with because the filament is only loaded when the print actually starts, so this may be an issue with the MK4s too, but this is the first time I'm experiencing this issue and its with the Core One.
RE: Nozzle cleaning consistently fails with PETG
Since there's that extra 20 mm Y axis at the front of the machine I'm experimenting with a silicone "brush" (intended for a BL mini) attached to the front of a longer print sheet, and I have the gcode set to do quick scrub before the Prusa "nozzle cleaning". This type of thing has been done with the i3 series but there's extra room for it on the CORE so you won't lose any print area).
I had two nozzle cleans fail after PCCF prints due to a little bit of filament left on the nozzle, so I'm going to see if this prevents that.
Various other printers have nozzle cleaning stations -- silicone brushes or lips, or some other structure over which the nozzle is swiped across a few times before the start of a print.
Is there a retrofit solution which integrates well with the Prusa printers? Hardware-wise it should not take up too much of the addressable print space; software-wise the slicer and/or the printer should know about the blocked area, and the wiping should ideally be automatically performed before every print. Does such a solution exist for the Mk3/4 printers, or even adapted to the Core One already?
Working on the same idea. Let's see what both of us came up
RE: Nozzle cleaning consistently fails with PETG
I posted my attempt in the User Mods section https://forum.prusa3d.com/forum/user-mods/silicone-brush-on-print-sheet-for-improved-nozzle-cleaning/
RE: Nozzle cleaning consistently fails with PETG
I have exactly the same issue with my CoreONE. Few more observations: 1] HF nozzle makes it worst. 2] Higher the temperature material needs, the worst it is. For ASA or PCCF it's real nightmare to get the print started. 3] Non CoreONE print sheets - which are basically all except for the new smooth PEI coming along with the printer - are more prone to this issue. I think this is because of the text printed at the right front corner which makes the sheet not to be 100% smooth what makes the printer thinks the nozzle is not clean. MK4/S does this exercise at the left side which has no prints on it. New CoreONE smooth sheet doesn't have any prints in the 'nozzle cleaning area'. It's just my theory though...
RE: Nozzle cleaning consistently fails with PETG
I have exactly the same issue with my CoreONE. Few more observations: 1] HF nozzle makes it worst. 2] Higher the temperature material needs, the worst it is. For ASA or PCCF it's real nightmare to get the print started. 3] Non CoreONE print sheets - which are basically all except for the new smooth PEI coming along with the printer - are more prone to this issue. I think this is because of the text printed at the right front corner which makes the sheet not to be 100% smooth what makes the printer thinks the nozzle is not clean. MK4/S does this exercise at the left side which has no prints on it. New CoreONE smooth sheet doesn't have any prints in the 'nozzle cleaning area'. It's just my theory though...
I'm experiencing the same issue, first observed on my initial PETG prints. At the same time, I had also switched over to the Prusa satin sheet (which has the labeling in the lower right corner as described above).
"when a cleaning fails, prepare for war"
- The Pact
RE: Nozzle cleaning consistently fails with PETG
I installed my wiper (found under user mods) Since then not one single fail
RE:
Also, I don't really want to sit and baby sit my prints for the first 5-10 mins each time.
Tough.
It was usual with early RepRap machines to watch the first two or three layers in case of early fails. Prusa Mk2 reduced it to watching just the first layer and Mk3 just to watching all the first layer perimeters and the beginning of infill. With my XL I glance a few times at only the first two perimeters and then walk away. The Core One is of the same generation, I would expect to monitor the the first two perimeters.
A few minutes at the start when the whole print may take hours or even a few days is trivial.
Cheerio,
I don't understand the 'it used to be worse so why try to keep improving on it now since its better' mentality. Nothing would ever improve if everyone lived by that. It's clearly still an issue, even if its not as bad as it was. And its also a largely fixed issue.
There are multiple things to unpack here:
- There is something inherently wrong with the nozzle cleaning step
If it isn't happy with the readings during cleaning after 5 probes it will do all 20 probes and fail. I've never had a nozzle cleaning stage conclude without error after the 5th probe. This is an error
It also doesn't really do any cleaning, especially on certain steel sheets. Nothing comes off the nozzle during the probing unless using the smooth sheet
These were my main concerns when making this post in the first place, the nozzle cleaning stage just seems to not work properly - There ARE solutions to this issue outside of poking the build plate over and over
Other manufactures and also user mods add a silicone/similar brush and a scrubbing phase. Which just automates the cleaning with a brush before a print without the worry of the Core One crashing when the door is opened, which happens all the time and will be fixed eventually, but isn't yet.
I have never had a clean fail or a print fail with my MK4 with MMU3. This is because it doesn't load the filament until it starts printing. This eliminates the possibility for oozing. I would start a print remotely and it would just print without supervision. I had a camera to make sure it was working, but didn't need to baby sit it with a wire brush. - There are also likely other solutions i.e.
Retract the filament more after a print when the nozzle is cooled slightly to try and pull most of the plastic out of the heat zone
Wipe the nozzle over the build plate instead of just poking it (I'm pretty sure there is custom GCode in the Core One test prints on the USB to do this
I can't imaging its fun if you have a print farm of 5, 10 or more printers to have to sit scrubbing the nozzle on each printer at the start of every print so that your print doesn't fail during a stage which is meant to clean the nozzle, that just seems like a big problem to me. But hey, I guess we are just meant to baby sit our print farms because it used to be way worse.