Can a Mk3 fly ?  

Re: Can a Mk3 fly ?

Are you running in an enclosure? Maybe just high ambient temperatures?

I haven't had any issues since I started actively venting my enclosure with a 120mm fan running full blast to suck air out. I had my extruder motor getting pretty hot on a >50hr print, so I've since added this guy to keep the extruder cool. https://www.thingiverse.com/thing:3339228

I haven't installed my MK3S upgrade yet, so I don't know if I'll need to tweak the design to fit the new extruder, but if you're still on the MK3 extruder this will fit just fine.

Re: Can a Mk3 fly ?

I have had my Mk3 for just over 6 months and it has developed the dredded clicking (extruder/nossle block) issue. [...]

Early last year, I put together my notes on how I dealt with the extruder clicking issue. Since then, additional culprits became commonplace:

Are you getting actual blockages and quality problems? Some clicking is normal with retractions.

Re: Can a Mk3 fly ?

...I have changed the PTFE tube 5 times, and just changed the hot end completly (all parts from E3D and rebuilt complete new one).
After hot end replacement all was good for about 5 prints then clickng returns with the dreaded filament bulge at the top of teh PTFE tube....

I would start searching for the root cause instead of keep changing PTFE tube.
If you want some good hints, you need to provide as much information as possible. Starting with used filament, Object you're printing and all slicer settings.

Re: Can a Mk3 fly ?

Sorry to hear about your troubles. A couple things I can think of, but I don't guarantee that any or all will work... (Also, I'm a fellow user and don't represent Prusa.) You may have checked these items, but you didn't mention it in your email.

If all else fails, this might be the inspiration you need to get started on that trebuchet project you've always wanted to do. 😉 Seriously, I hope you are able to resolve this. If my blind guesses aren't enough, hopefully someone else can help.

Re: Can a Mk3 fly ?

Thanks for you comments/suggestions, I have added more info.

I get filament buldge at the top of the PTFE then the filement snaps of if a try to pull it out (hotend to temp and extruder gear released).

Printer is in an enclosure but temp does not get above 30 degrees C.

I replaced the heatbreak with a new one from E3D for Prusa Mk2/3, so I think it still has the known issue, how do I get the correct one?

Prusa LiveChat just suggested changing the nossle, this is after I said I changed the whole hot end, not sure if its a case of dont know or dont care.
£700 on something that fails in 6 months ... this is crazy

Re: Can a Mk3 fly ?

Are you using one of these to lock the collet and in place so the PTFE can't move upwards?

https://www.thingiverse.com/thing:2585970

Re: Can a Mk3 fly ?

Thanks Christopher ... some good points but I have indeed tried them.

Nikolai - The problem is not on a specific model/file it has happened on a number of models including a Benchy. I am using Prusament PLA, SLic3r, 0.2mm, default settings, ambient no more than 30 degrees C, rerun self tests including PID, first layer is textbook, failure normall happens about 30% through a print (give or take 20%). Never on first layer.

Re: Can a Mk3 fly ?

Frio - Thank you for the suggestion. originally there was no lock on PTFE, but when I replaced the hotend and heatsink I put one on (came with replacement parts from E3D).

Re: Can a Mk3 fly ?

Just throwing out ideas here but have you tapered the inside outside of the lower end of the PTFE tube?

Maybe there's something in here:
https://e3d-online.dozuki.com/Wiki/V6_Troubleshooting

Re: Can a Mk3 fly ?

Frio - All ideas are welcome :-). But yeah I tried that, actually I bought replacement PTFE from Prusa.

Hmm Prusa LiveChat just said Prusament PLA is not designed to be printer in ambient as high as 30 degrees C.

Re: Can a Mk3 fly ?

Frio - All ideas are welcome :-). But yeah I tried that, actually I bought replacement PTFE from Prusa.

Hmm Prusa LiveChat just said Prusament PLA is not designed to be printer in ambient as high as 30 degrees C.

Based on your description I would also assume it. Make sure you're using R3/R4 extruder and lower the ambient temp to ~20C. This way you can rule out if it's a heat creep issue.

Re: Can a Mk3 fly ?

Nikolai - Just put Prusa in freezer trying to drop ambient to -20C 🙂 Sorry you have been very helpful but I could not resist the typo pickup I guessed you meant drop to 20C. Is R3/R4 extruder the one with the fan at an angle? If so I have that.

LiveChat said to leave front of enclosure and to check extruder motor temp .... Can you tell me more about the heat creep and ideally how to fix it, as extruder motor feels about 50C, much hotter than Z motor and close to bed temp (60C) when ambient now 24C. Strange how it worked for several months and now fails (yeah I know it was winter but ambient always around 20-25C).

Re: Can a Mk3 fly ?

Further update:
I did some checking on heat creep as I was not sure what it was, I dont think I have that problem.
I think the problem I have is extruder motor getting hot especially in an enclosure resulting in heated extrusion gears approacing the glass transition temperature of PLA.

Re: Can a Mk3 fly ?

lol. Yes, with -20C you will get another issues :).
You might be right in regards to the motor. Anyway lowering the ambient temp might solve the issue. Make sure to release the tension on the bondtech gears. Maybe your motor is getting higher resistance pushing the filament through.

Re: Can a Mk3 fly ?

Some thoughts:
1. Did you check if perhaps the nozzle temperature drops during printing?
2. Use a 0.6mm nozzle;
3. Try to get cooler "outside enclosure air" to the extruder. I have build this: https://www.thingiverse.com/thing:3502557 ;
4. Use an upgraded extruder design so the filament path is fully aligned with the gears (e.g. this one: https://shop.prusa3d.com/forum/user-mods-octoprint-enclosures-nozzles--f65/modified-c1-r4-mk3s-parts-better-filament-path-and-t28334.html#p133592 . You should be able to push and pull a loose piece of filament easily in and out of the extruder, so that the motor smoothly rotates.

Good luck!

Remember: the journey is as important as the destination...

Re: Can a Mk3 fly ?

Another update:

It appears the extruder motor getting hot is a known issue (one that a firmware change was made to help reduce the impact)
https://github.com/prusa3d/Prusa-Firmware/issues/780
https://shop.prusa3d.com/forum/hardware-firmware-and-software-help-f64/extruder-motor-gets-extremely-hot-would-heatsinks--t17635-s10.html
just a couple of examples there are more and some on redit.

For me it appears irrisponsible at the very least for Prusa to promote the use of enclosures when they know there is an issue with extruder motors getting hot which will be made worse in an enclosure. Also not to highlight issue in the first place. I guess corporate growth is more important than user expereince to Prusa these days.

This may not be the case for all Mk3 printers, indeed for issue 780 Prusa sent a replacement motor so it may only be some unlucky people who were given a bad extruder motor.

So I have spent over £100 in parts (offcial parts) and countless hours dissassembling and reassembling for an issue known to Prusa and made worse by my following the Prusa promoted idea of having an enclosure. Very unhappy!

Re: Can a Mk3 fly ?

Check the first reply to your original post for a solution to a hot motor inside an enclosure.

Re: Can a Mk3 fly ?

For me it appears irrisponsible at the very least for Prusa to promote the use of enclosures when they know there is an issue with extruder motors getting hot which will be made worse in an enclosure. Also not to highlight issue in the first place. [...]

Near the top of the Prusa blog entry, it states:

[...] However, if you’re not printing with ABS or other high-temperature filaments that suffer from warping, you won’t see much of a difference. You might actually want to keep the enclosure open with, for example, PLA to ensure there’s enough cool air around the printer for the part cooling fan.

I got excited about the idea of a Lack enclosure until I read that very article and noted it would do very little for me. An enclosure can still be useful for keeping the printer clean and reducing noise, but with any piece of machinery, proper cooling is important. Aside from the extruder motor, you also have to keep the E3D V6 hotend itself operating within guidelines. After searching the E3D site for a bit, I found a reference indicating that the hotend itself is only rated to 40C ambient temps. This means that, although the printer can circulate air for cooling, that air has to be at an appropriate temp.

Enclosures work well if used properly, but you do want to know that the limitations are based on your own specific local conditions. No one set of guidelines is going to work for everybody.

I'd still suggest trying to narrow down why that motor is getting so hot in the 1st place. That's certainly not universal on the Mk3.

Re: Can a Mk3 fly ?

Indeed Karl - first response by you called it well. Thank you.
I have to admit as ambient was only 30C I did not think that would be the issue.

bobstro - Prusa post may say about considering leaving enclosure door open for PLA, but it mentions for part cooling fan, part cooling for me worked OK. I think they should at least add that Extruder motor could get hot and cause issue with PLA.

I have an infrared thermometer coming today so I can try to find out what impacts the extruder motor temp, filament tension should be fine but will experiment. Also have heatsinks coming as a last resort, but thats hiding the problem not fixing.