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Bed levelling failing due to goop on nozzle  

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paul.a13
(@paul-a13)
Eminent Member
Bed levelling failing due to goop on nozzle

I'm finally close to getting my Mk3 back to something resembling acceptable operation after being returned to Prusa for inspection, replacing the hot end, and having the most frustrating time of my life trying to successfully print the R3 parts on a printer which doesn't work properly. I'm working on ironing out the last few wrinkles, but I've got one bugbear which has been with me since I first assembled it, and just won't go away. Maybe one out of every 3 or 4 prints I get the "Bed leveling failed, check nozzle for debris, waiting for reset" error message. I've tried everything I can think of to do with calibration, nothing improves it. The thing is, I know what causes it - it only ever happens when PLA builds up around the nozzle during pre-heating, which then bunches up and causes the error during leveling. I mentioned this to Prusa support some time ago and was told "It's not a bug, it's supposed to do that." Seriously. So it's supposed to abort prints 30% of the time? I really don't think so.

Anyone else had this pre-print goop issue and found a way around it?

Respondido : 09/09/2018 4:11 am
Peter in Katy
(@peter-in-katy)
Estimable Member
Re: Bed levelling failing due to goop on nozzle

Clean the nozzle between prints. As the nozzle heats up for a print, inspect it. You'll see it start to ooze. Make the ooze go away.

Get a brass brush. Fold a paper towel over a couple times and grab the goop.

Respondido : 09/09/2018 2:23 pm
bobstro
(@bobstro)
Illustrious Member
Re: Bed levelling failing due to goop on nozzle

+1 for regular cleaning of the nozzle. Anything that accumulates on the nozzle or hotend is eventually going to come off, whether in your bed leveling routine, or mid-print.

I've modified my startup gcode to raise Z and move the bed forward as the nozzle heats to give me a chance to clean both before each print. I make a point of inspecting the nozzle and hotend for any accumulated crud then.

My notes and disclaimers on 3D printing

and miscellaneous other tech projects
He is intelligent, but not experienced. His pattern indicates two dimensional thinking. -- Spock in Star Trek: The Wrath of Khan

Respondido : 09/09/2018 9:36 pm
kbx
 kbx
(@kbx)
Eminent Member
Re: Bed levelling failing due to goop on nozzle

I'm not the OP but I would be very interested to learn how to do that bobstro
I think we all encounter that and deal with it (manually myself) but if there's an automated method where I can snag-it and print...

Respondido : 09/09/2018 10:44 pm
kbx
 kbx
(@kbx)
Eminent Member
Re: Bed levelling failing due to goop on nozzle

Bump 😉

Respondido : 10/09/2018 9:51 pm
bobstro
(@bobstro)
Illustrious Member
Re: Bed levelling failing due to goop on nozzle


I'm not the OP but I would be very interested to learn how to do that bobstro
I think we all encounter that and deal with it (manually myself) but if there's an automated method where I can snag-it and print...

Well... here's more than you asked for! 😀

The lines for doing the pre-print raising for cleaning are 4, 9-10. I set a moderate "no-ooze" nozzle temp (140C with Slic3r, varies by material), home then raise the extruder and push the bed forward and wait for the nozzle to come to temp. This gives me a few seconds to clean the nozzle and bed and generally look things over before the print starts. It also has a side benefit of letting the PINDA cool down as it will wait until the nozzle cools to 140C if it's already hot.

Starting at line 11, I pull the nozzle back down to the bed and wait for the PINDA to warm up to 35C to ensure a consistent temp for bed leveling. This requires the bed be warm enough to ensure the PINDA will actually heat up, thus line 5. I'm not sure how necessary this is, but I've had very good consistency and no 1st layer problems since starting to use this routine. The only downer is that I can't print status messages and it sometimes takes 5-10 minutes for the PINDA to warm up when cold, so it's not good for the impatient. Line 23 sets the bed to the final print temp.

Most of this is assembled from various threads here on the Prusa forums. You can easily tweak this to suit your own needs.

My notes and disclaimers on 3D printing

and miscellaneous other tech projects
He is intelligent, but not experienced. His pattern indicates two dimensional thinking. -- Spock in Star Trek: The Wrath of Khan

Respondido : 10/09/2018 10:10 pm
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