PLA melted by extruder motor in MK3S  

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byCx
 bycx
(@bycx)
New Member

I flawlessly build my MK3S and it worked perfectly. I started printing models available on the Prusa's SD card. First prints were fine, they were small. But when bigger prints came, like the Castle, the extruder motor was hot enough to heat Bondtech gear up so much it started melting the filament before it got into the PTFE tube. Clicking occurred and no filament from the nozzle was coming. It happened a few times until I wasn't able to get the filament from the PTFE tube out. I started removing parts of the extruder just to learn out one of the nuts got loose and I can't remove the screw. I had to use brutal force to get part holding the hotend out. The support chat was very helpful in this phase of my misery. They promised me a new extruder motor but I am not sure that's the problem.

The first fail was probably caused by my enclosure. It got to 40 °C inside and that's pretty high. I opened it for another one and it was ok. I tried to print for the second time overnight. Room doors were closed, the temperature got over 30 °C and it failed after a few hours of printing. I couldn't get the filament out and it triggered a chain of catastrophic events and decisions ended in having the printer with destroyed extruder printed parts completely.

I am printing new parts on my good old MK2 and going to try to assemble it again. My room, where the printer is, is pretty hot. In summer it's around 30 °C. I won't be using encloser for some time but I would like to ask you, in what temperature do you use your printers? Do you know what temperature your extruder motor is? (Mine is ~50 °C without encloser) And also have you experienced a similar issue in your MK3 and MK3S? Have you found any solution? I don't want to add another fan to "fix" it.

I am surprised by this because my MK2, upgraded from MK1, has been printing without any issues for more than three years.

Melted PLA

Stuck screw

 

This topic was modified 1 year ago by byCx
Posted : 24/04/2019 1:51 pm
Tim
(@tim-m30)
Illustrious Member

Prusa has a CHAT available in their STORE website.  Log in like you are going to buy something and CHAT is available lower right of the screen.

It is always wise to get more than one opinion......
Posted : 27/04/2019 1:22 am
byCx
 bycx
(@bycx)
New Member

Thx, but I talked to the support already. The new extruder motor is sitting on my table. Haven't had time to replace it yet.

There is GitHub issue related to my problem: https://github.com/prusa3d/Prusa-Firmware/issues/1757

Posted : 27/04/2019 11:58 am
joan.t
(@joantabb)
Veteran Member Moderator

the mk2 hobbed gear was smaller diameter than the Bondtech hobbed gear pair on the mk2.5, mk3 and mk3s, so the Mk2 was effectively in a lower gear...     therefore the motor didn't have to work as hard to achieve the printing pressure on the filament. 

the motor for the bondtech setup is probably run at a higher current to drive the extruder, causing the higher temperatures. 

I have never had a problem with this, but other folk have had problems in enclosures, and higher temperature climates

have you got the latest firmware on your printer?   some of the updates reduced extruder heating...

Stealth mode/ Silent mode, might cool things down a bit for you!

Good luck, Joan 

I try to make safe suggestions,You should understand the context and ensure you are happy that they are safe before attempting to apply my suggestions, what you do, is YOUR responsibility. Location Halifax UK...
Posted : 27/04/2019 3:00 pm
Tim
(@tim-m30)
Illustrious Member
Posted by: byCx

Thx, but I talked to the support already. The new extruder motor is sitting on my table. Haven't had time to replace it yet.

There is GitHub issue related to my problem: https://github.com/prusa3d/Prusa-Firmware/issues/1757

50c is not especially hot; but inside an enclosure that limits ambient to 40c it can easily reach 65c and higher, and more easily cause the symptoms of soft PLA and resulting extrusion issues. If I recall the threads on this, most people having melted filament at the gear were using enclosures.  E.g., My X and Y motors are just as hot as my extruder, and they hover around 45c-55c when operating on models with lots of movement and extrusion.  Not once have I melted the filament at the Bondtech running in a 25c room.

Simply changing the motor probably won't help, unless you change to a motor with different windings; but then you also risk changing print characteristics and face retuning all of the extruder settings in your slicer and even firmware.  A philosophical decision.

It is always wise to get more than one opinion......
Posted : 27/04/2019 6:17 pm
byCx
 bycx
(@bycx)
New Member

Right now after 6h of printing outside of encloser:

E: 53 °C (Definitely different from others)
Z: 42 °C both motors
Y: 40 °C
X: 40 °C

Rest of the temperatures:

Room: 27 °C

Ambient: 56 °C
Pinda: 36 °C
Bed: 90 °C
Nozzle: 239 °C

I tried PLA with opened encloser and it melted. I will try again without encloser at all. I have been printing from PETG so far because it's working fine.

I am aware of what you are telling me and I don't think there is something wrong with the motor either. But still, compare to MK2, MK3S is super sensitive about the ambient temperature when PLA is in the game. 

Posted : 27/04/2019 6:44 pm
konrad.s
(@konrad-s)
Active Member

Hiho,

 

have you got further information for us, in the meantime?

A few days ago i printed quite much, nearly continuously 4 hours and suddenly there came no further filament out of my etruder, because of:

please remember, this blockage is on the upper side of the gears, on this side where the filament is guided into the extruder body. 

After the 4h of printing the extruder motor was very hot, this much hot, that i could not touch it.

Have you found any solution for this?

Posted : 14/05/2019 10:22 pm
gnat
 gnat
(@gnat)
Prominent Member

I've done a few 11-12 hour PLA prints since upgrading to the 3S and haven't seen this issue (no enclosure). I haven't measured it, but currently (4.5 hours into a print) the extruder motor is hot enough that I don't want to hold my finger on it. Anecdotally I don't recall it ever feeling so hot (not that I touch it frequently) prior to the upgrade even at the end of a 55 hour print.

One change I have noticed is that with the old MK3 setup I could usually manually push filament through and pull it out even with the idler door closed (though it was much easier with it open). On the 3S, however, I can't manually feed filament or pull it out even if I remove the door (MMU tower). I had to rebuild the extruder this weekend due to a jam and it came out the same (so I don't think it's an assembly issue). That would suggest that there is more resistance which would require the motor to work harder and thus more heat.

MMU tips and troubleshooting...
Posted : 14/05/2019 10:40 pm
karrie liked
vintagepc
(@vintagepc)
Noble Member
Posted by: gnat

One change I have noticed is that with the old MK3 setup I could usually manually push filament through and pull it out even with the idler door closed (though it was much easier with it open). On the 3S, however, I can't manually feed filament or pull it out even if I remove the door (MMU tower). I had to rebuild the extruder this weekend due to a jam and it came out the same (so I don't think it's an assembly issue). That would suggest that there is more resistance which would require the motor to work harder and thus more heat.

This may be related to the hotend offset. The butterworth design fixes the fact the filament is not centered because the gears aren't centered on the hole. Manual push and cold pulls are a lot easer now that I switched to said design.

Posted : 14/05/2019 10:43 pm
karrie liked
bobstro
(@bobstro)
Illustrious Member
Posted by: konrad.s

[...] Have you found any solution for this?

Things to try:

  • Slow down the print and see if that helps. You may be pushing filament at a rate the hotend simply can't process quick enough. This can create back-pressure which can extend up into the extruder. If filament can't move, the gears grind on it, adding more heat. Dial back speeds using the front knob and see if that helps.
  • Check for excessive retractions. Too many retractions can cause the extruder motor to do extra work, adding to heat build-up.
  • With the E3D direct drive extruder, retraction lengths should be kept below 2mm. Any longer and you're pulling molten filament back up into the cold zone.
  • Be aware of ambient temps. The E3D V6 hotend is air cooled, and rated to work at up to 40C ambient temps. More than that, and it will have a hard time cooling properly. Open enclosure doors or remove panels. Remove any fancy fan guards or other goodies that can block airflow. Improve air circulation.

You are trying to fix a problem that can have many causes. Try keeping things simple and when in doubt, slow down. I've got a big dump of related notes that you can check for other ideas.

This post was modified 1 year ago by bobstro
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...
Posted : 14/05/2019 10:46 pm
gnat
 gnat
(@gnat)
Prominent Member
Posted by: vintagepc
Posted by: gnat

One change I have noticed is that with the old MK3 setup I could usually manually push filament through and pull it out even with the idler door closed (though it was much easier with it open). On the 3S, however, I can't manually feed filament or pull it out even if I remove the door (MMU tower). I had to rebuild the extruder this weekend due to a jam and it came out the same (so I don't think it's an assembly issue). That would suggest that there is more resistance which would require the motor to work harder and thus more heat.

This may be related to the hotend offset. The butterworth design fixes the fact the filament is not centered because the gears aren't centered on the hole. Manual push and cold pulls are a lot easer now that I switched to said design.

Ran off the MK3 and MK3S versions yesterday and overnight. A few more tweaks to test this week, but I expect to rebuild this weekend. Probably going back to MK3 firmware if I do. 

MMU tips and troubleshooting...
Posted : 15/05/2019 12:08 am
peter.m26
(@peter-m26)
Honorable Member

The infil speed off 200 mm is to fast, slow this down to 150 or 100.

On big models it gives problems, big flat models.

 

On thingiverse you can find a extra fan to mount on the extruder to cool extra down, i have installed this, with a extra phone power adapter.

i adjusted the thingi versu print a little bit, so i do not need to glue it.

 

Also i am making a extra big fan to blow in my enclosure wenn printing pla with doors open, blow in the enclosure on the lower parts of the eclosure, warm air goes up, otherwise you will block warm air to the lower part if you blow cold air in the top off the enclosure.

Posted : 15/05/2019 12:29 pm
gregory.b10
(@gregory-b10)
Trusted Member

I'm having similar problems as noted in two previous posts.  Sent an email to the Prusa info account a couple days ago and haven't received a response.  I'll post updates in my most recent thread but I'm getting tired of fighting this thing.

How are we supposed to use more advanced materials if there are chronic heat problems?

This post was modified 1 year ago by gregory.b10
Posted : 15/05/2019 12:41 pm
gnat
 gnat
(@gnat)
Prominent Member
Posted by: gregory.b10

I'm having similar problems as noted in two previous posts.  Sent an email to the Prusa info account a couple days ago and haven't received a response.  I'll post updates in my most recent thread but I'm getting tired of fighting this thing.

How are we supposed to use more advanced materials if there are chronic heat problems?

Log into the shop and use the chat. It's much more reliable/fast than email.

In regards to materials, this only seems to be an issue with PLA. Higher temp (ABS/PET) materials seem to do fine and slower speed materials (TPU) also appear OK. 

Not that this isn't an issue, but if you wanted to print the Butterworth mod you should be able to do so. 

MMU tips and troubleshooting...
Posted : 15/05/2019 12:49 pm
bobstro liked
gregory.b10
(@gregory-b10)
Trusted Member
Posted by: gnat
Posted by: gregory.b10

I'm having similar problems as noted in two previous posts.  Sent an email to the Prusa info account a couple days ago and haven't received a response.  I'll post updates in my most recent thread but I'm getting tired of fighting this thing.

How are we supposed to use more advanced materials if there are chronic heat problems?

Log into the shop and use the chat. It's much more reliable/fast than email.

In regards to materials, this only seems to be an issue with PLA. Higher temp (ABS/PET) materials seem to do fine and slower speed materials (TPU) also appear OK. 

Not that this isn't an issue, but if you wanted to print the Butterworth mod you should be able to do so. 

Thanks.  I was under the impression PLA was wondermaterial but want to experiment with PETG.

Posted : 15/05/2019 2:20 pm
gnat
 gnat
(@gnat)
Prominent Member
Posted by: gregory.b10
Posted by: gnat
Posted by: gregory.b10

I'm having similar problems as noted in two previous posts.  Sent an email to the Prusa info account a couple days ago and haven't received a response.  I'll post updates in my most recent thread but I'm getting tired of fighting this thing.

How are we supposed to use more advanced materials if there are chronic heat problems?

Log into the shop and use the chat. It's much more reliable/fast than email.

In regards to materials, this only seems to be an issue with PLA. Higher temp (ABS/PET) materials seem to do fine and slower speed materials (TPU) also appear OK. 

Not that this isn't an issue, but if you wanted to print the Butterworth mod you should be able to do so. 

Thanks.  I was under the impression PLA was wondermaterial but want to experiment with PETG.

It is a great material, but a downside of it's lower melting point is that it is more susceptible to ambient heat issues.

I would suggest starting with Amazon's PETG to start with on the PETG front. It has a lower temp rating than most (230 is what I've been using) and doesn't stick to the PEI bed as harshly most talk about. The .2mm prints I've done aren't as good as PLA, but near enough. Here is my setup to help get you started:

  • Amazon PET-G
  • Start with the Prusament PET-G profile
  • Set the extruder temp to 230 for the whole print.
  • Turn the part fan off for the entire print if there is no small detail.
    • Turn it on 5ish layers before starting any detail work, but not in the first 10 layers.
  • Same bed prep I use for PLA (but I don't use the same side of the sheet)
    • Infrequent: Water and dish soap bath
    • Infrequent: Acetone wide down
    • Before heating bed: 99% IPA wipe down
MMU tips and troubleshooting...
Posted : 15/05/2019 4:00 pm
bobstro
(@bobstro)
Illustrious Member
Posted by: gregory.b10

How are we supposed to use more advanced materials if there are chronic heat problems?

PLA is known for being user friendly, with good bridging and overhang results with lower heat. Ironically though, it's the material that is most likely -- or at least very likely -- to trigger these problems. Because PLA is so easy to work with, it melts quickly in the hotend and starts to push up against the capacity limits when you print with increased layer heights, extrusion widths or speeds. Thick is often what is encountered with the "extruder click" or "heat creep" scenarios, resulting in alarming clicks and possible jams.

The "chronic heat problems" are often the result of users not contemplating the impact of ambient temps on an air cooled device. If your ambient temps approach the 40C upper limit that the E3D V6 extruder (used on may high-end printers) is capable of functioning in. So yes, the Prusa printers, like any other air-cooled printer, need to operate within spec.

Besides ambient temps, there are factors we have more control over. Setting max volumetric speed (MVS) appropriately for your filament helps tremendously, automatically slowing down printing when you exceed the hotend limit you set, but not otherwise restricting speeds. Simply dialing back MVS will help in many of these cases. So to answer your question: A deeper understanding of the limitations of the hotend capacity and materials being printed will allow printing with more advanced materials. There are other factors such as bed adhesion that are equally important to understand.

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...
Posted : 15/05/2019 4:30 pm
peter.m26
(@peter-m26)
Honorable Member

https://www.thingiverse.com/thing:2975582

Extruder cooler, keeps it very ccool, blow to the top.

And i change the heater cardrige to original E3D, because of movie /forum complaints of this is to wide, and fillamnet, gets heated to soon, and gets stuk.

NO MORE JAMS on the Prusa i3 mk3 3D Printer!

Posted : 16/05/2019 9:46 am
Vojtěch
(@vojtech-p6)
Honorable Member

One reason why the E motor gets very hot (and starts melting PLA) is when the springs are too tight. The more tight they are, the harder the motor has to work, the more heat is produced. Check that you have not overtightened the door screw on the Mk3s and that, particularly the idler gear, turns smoothly. 

Posted : 16/05/2019 1:18 pm
Nigel liked
Wouter Himschoot
(@wouter-himschoot)
New Member

Hi guys,

I'm having exactly the same issue for over 1 year now like bycx. As soon as I've created a very nice enclosure, the PLA jammed immediately after 1h printing. Tried with ABS and ABS+, they also jam but after a much longer time.

To be honest, I feel a bit disappointed. Without enclosure my prints warp. Even PLA when printing big parts. In belgium the temperature in my workshop is also going from 10°C in the winter to 25°C in the summer. Therefor an enclosure is really necessary.

I do understand that the extruder gear limit should be max 40°C. I'm hoping that PRUSA can develop an additional part to mount somewhere on the side of the extruder gears, so it can be cooled extra. Standard design now is only cooling the aluminium extruder itself, not above. My PLA always melts just at or below the extruder gears. Mostly I have to disassemble the whole extruder :-s

To only way I guess is to install a fan on the gears, with a tube which goes outside the enclosure backside and sucks in cold air for cooling. Will try to make this...

Posted : 01/04/2020 4:41 pm
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