New Prusa MK3S, extruder jammed  

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Nick-i3mk3s
(@nick-i3mk3s)
Eminent Member

Hi everyone,

I purchased an i3 MK3S kit a month ago, and the first prints came out just fine.

However earlier this week the first print failed halfway without clear indication of cause. It appeared as if the printer simply stopped extruding randomly. The filament was jammed in the extruder, and because the extruder stepper tried to push it through it thickened outside the white tube, after which the filament broke right above the tube entrance. After prying it out and reloading filament, the Prusa printed fine for another few prints.

Yesterday the second print failed, almost at the end of the print, with the same symptoms: extruder seemed to have stopped extruding randomly. Fortunately filament could be unloaded and reloaded just fine, and print restarted.

Today same issue, third print failed after about 1 hour (of a 5 hour print), with the printer no longer extruding. The filament again broke off just above the white tube and had to take the extruder assembly apart. When reloading filament, the extruder stepper skipped steps, and I discovered there is something jammed inside the extruder itself.

I can stick the needle through the hot end for a few cm but then it hits a blockage. Pushing filament through the normal side also hits a blockage. I tried ramping up the temperature to 250°C to melt whatever might be stuck in it, but that didn't seem to help either. Whatever I try, I can't seem to remove the blockage.

I don't really know what to do next, could someone help please? I'm out of ideas after hours of trying. Useful to mention is that I'm printing with the silver PLA that came with the printer kit, and it's printing in a dry room.

Thanks!

Posted : 30/05/2019 7:08 pm
Peter M
(@peter-m)
Prominent Member

is your heatbreak and ptfe tube and heatsink, build OK,  no gaps allowd.

Check forum and youtube how to rebuild this, and adjust this.

Slower speed you could try,

different filament,

and the prusa settings in slicer are for optimal speed, often you need to change settings,

slower, more heat, big brim attached to model, etc.

 

You could try to print with more heat, if your extruder skips steps.

You can check this by printing a big flat square,  then you see if the printer fails, because of the high speed.

In the pass I had bad filament, that needed 20 degrees higher otherwise the extruder skips(or print slower).

 

And i saw a movie on youtube that prusa has a bigger heatbrake, and that filament(pla) get stuck above the heatbrake, this was for a certain brand filament, and that higher temps should help.

 

Print in a enclosure? to much heat for pla,

i have a extra fan on the extruder, that blows air to the top, away from the extruder, so the extruder stays cool(on thingiverse you can find this), and no heat can go the filament.

And a extra fan to blow in the case could also help, or more windows to open in the enclosure.

 

Posted : 31/05/2019 1:52 pm
Peter M
(@peter-m)
Prominent Member

Check if your pin in the extruder wheel are in the middle and not to one side, then strange things can happen.

This post was modified 2 years ago by Peter M
Posted : 31/05/2019 2:05 pm
Nick-i3mk3s
(@nick-i3mk3s)
Eminent Member

Extruder wheel and PTFE tube appear to be lined up correctly, so it doesn't look as a likely cause of the trouble.

I have the impression the jam occurs as follows:
- a blob forms in the lower part of the hot end, preventing the filament from being extruded because it can't fit through the nozzle anymore
- extruder stepper keeps pushing filament, which eventually deforms at the entrance of the PTFE tube into another blob
- filament then breaks off right above that blob, between the PTFE tube entrance and the extruder wheel
- filament is now jammed in the hot end and can't be removed either way because there is a blob with a diameter wider than the PTFE tube on either side

The first time this happened I managed to get it out without much problems, but this morning the PTFE tube deformed while getting the filament out of it. Ordered new piece of PTFE tubing, waiting for it to arrive to test.

I will try printing the PLA at a higher temperature, hoping to avoid the blockages from forming that way.

Posted : 07/06/2019 12:16 pm
bobstro
(@bobstro)
Illustrious Member

Try some cold pulls to clear any built-up crud in the hotend or nozzle. You may have a partial clog at the root of your issues. A nozzle swap may be in order. 

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 : 07/06/2019 1:53 pm
Nick-i3mk3s
(@nick-i3mk3s)
Eminent Member

Thanks for the input, bobstro. I've checked the channel and nozzle, however, and there are no signs of material partially clogging the nozzle. It appears that the cause must be something else.

I should mention that often the printer prints for hours without problems and with high quality, and then suddenly jams again without clear cause.

Posted : 07/06/2019 2:11 pm
bobstro
(@bobstro)
Illustrious Member
Posted by: Nick-i3mk3s

[...] I should mention that often the printer prints for hours without problems and with high quality, and then suddenly jams again without clear cause.

You've done the basic troubleshooting, so that eliminates some common problems. The next likely culprit may be heat. As we move into the hot summer months in some parts of the world, we're going to see a lot of similar "extruder jam" and "heat creep" posts. Keep in mind that the E3D V6 hotend is air cooled, and only rated to operate in ambient temps up to 40C/104F. Any hotter and it can't shed heat via the heatsink, and heat can creep up into the coldend. PLA melts at relatively low temps, so softening filament can definitely cause the types of problems you've described. Obvious questions:

  • Are you printing in warm ambient temps approaching 40C?
  • Do you have good air circulation near the printer?
  • Are you printing in an enclosure with elevated temps?

Other common problems can be aggravated by hardware:

  • Have you inspected the feed path to verify that filament feeds easily into the extruder? Look for filament dust filters, filament guides and anything else that can snag and drag.
  • Have you opened the extruder door and verified that the idler wheel is stable and spins freely? If it jams or the axle is loose, it can jam and cause feed problems.

These kinds of symptoms can have many causes. I collected notes on a bunch of common issues last year. I need to add a few more, but you might skim my notes to see if something sounds like it could cause your problems. Please report back if you find the culprit so others can benefit! Good luck with it.

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 : 07/06/2019 3:09 pm
Nick-i3mk3s
(@nick-i3mk3s)
Eminent Member

Hi bobstro, thanks for sharing your thoughts! I don't think there are issues with dust or the idler wheel, everything seems well tied and properly aligned.

The possibility of elevated ambient temperature causing the issue is interesting, because the room I'm printing in is equipped with a dehumidifier (since I'm printing PLA), and the temp is usually ca. 30°C (although never close to 40°C as far as I know). Perhaps this makes cooling more difficult though, so I'll try lowering room temperature. Would adding a more powerful cold end fan be an option?

Posted : 07/06/2019 5:09 pm
Tim
 Tim
(@tim-2)
Illustrious Member

Increasing the air flow across theE3D heatsink won't affect the issue.

 

One way the extruder fails, adding to what Bob has stated, is the extruder motor runs warm: 55c to 60c.  In a warm room, it can get warmer.  This heat travels down the motor shaft to the filament drive gears. At some point they become warm enough to soften the PLA and extrusion stops.

There are designs for attaching heatsinks and  cooling fans to the E-Axis motor to reduce this issue.  I use a 40x40x15 mm heatsink applied with thermal tape, it reduces motor temperature about 8c.

Someone recently posted a Stepper Cooler to Thingyverse: https://www.thingiverse.com/thing:2975582  

 

Another common jam failure is when printing parts with a high number of individual regions where the printer must retract many time per layer. The higher the count of retracts in a layer the more likely this is to happen. A quick unload after a jam can identify the issue. If the filament has a stub at the end, and the stub measures 2.2 mm diameter, the heat break probably is the culprit.

 

It is always wise to get more than one opinion...
Posted : 07/06/2019 6:47 pm
bobstro
(@bobstro)
Illustrious Member
Posted by: Nick-i3mk3s

The possibility of elevated ambient temperature causing the issue is interesting, because the room I'm printing in is equipped with a dehumidifier (since I'm printing PLA), and the temp is usually ca. 30°C (although never close to 40°C as far as I know). Perhaps this makes cooling more difficult though, so I'll try lowering room temperature. Would adding a more powerful cold end fan be an option?

Prusa released updated R3 extruder parts last year that improved airflow for hotend cooling and a revised part cooling fan. If your part cooling fan is at an angle, you already have that installed. I've casually looked for fan replacements but haven't found any that provide significant improvements. I've seen a number of improved extruder designs that claim improved cooling.

Easiest might be to just make sure that hot air is pulled away by some air circulation. You don't want to blast the print with a fan, but some people have used table fans or other means to circulate the air. It might be worth a try just putting one nearby to see if it helps. I hate to run air conditioning for a printer. A ceiling fan might improve circulation enough to matter.

You might look at heatsinks and/or fans for the extruder motor. There are a few designs floating about. Here's one. I have not needed any of these measures myself, and have been able to resolve issues through a combination of reduced MVS, slower speeds and tuned retractions, but it really depends on what you're printing and some printer-specific factors.

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 : 07/06/2019 6:50 pm
Tim
 Tim
(@tim-2)
Illustrious Member

My extruder heatsink ...

It is always wise to get more than one opinion...
Posted : 07/06/2019 7:18 pm
Vojtěch
(@vojtech-3)
Honorable Member
Posted by: Tim

Increasing the air flow across theE3D heatsink won't affect the issue.

That doesn't match my understanding of cooling and heat-creep. An increased air flow would reduce the temperature difference between heatsink temperature and ambient temperature, improving resilience against heat-creep even in elevated ambient air temperatures.

One way the extruder fails, adding to what Bob has stated, is the extruder motor runs warm: 55c to 60c.  In a warm room, it can get warmer.  This heat travels down the motor shaft to the filament drive gears. At some point they become warm enough to soften the PLA and extrusion stops.

This is a separate cause, though, and here an increased air flow wouldn't help indeed. Decreased extruder motor current possibly could, although this could also lead to motor skipping (as opposed to filament grinding).

Posted : 07/06/2019 8:12 pm
Tim
 Tim
(@tim-2)
Illustrious Member
Posted by: Vojtěch
Posted by: Tim

Increasing the air flow across theE3D heatsink won't affect the issue.

That doesn't match my understanding of cooling and heat-creep. An increased air flow would reduce the temperature difference between heatsink temperature and ambient temperature, improving resilience against heat-creep even in elevated ambient air temperatures.

The creep in question is along the metal shaft directly to the filament by contact. The space where the gears are is unaffected by the airflow over the E3D heat sink. And filament is not thermally conductive to the point filament within the heat sink will conduct heat away from the gears. 

 

It is always wise to get more than one opinion...
Posted : 07/06/2019 8:18 pm
Vojtěch
(@vojtech-3)
Honorable Member
Posted by: Tim

The creep in question is along the metal shaft directly to the filament by contact. The space where the gears are is unaffected by the airflow over the E3D heat sink. And filament is not thermally conductive to the point filament within the heat sink will conduct heat away from the gears. 

So far I have only seen the term heat-creep used to refer to heating of the cold-end through the heatbreak and through heat carried to the cold end by the filament during retracts. The filament will then soften in the cold zone and cause a jam. To combat this, the increased airflow will help.

The E motor overhating and heating up the Bondtech gears as cause of jams seems to also be very real according to user reports, and usually results in grinding of the softened filament. And I do agree that a better extruder fan will not help here at all. A BMG upgrade does, as it breaks the thermal connection between the motor and the gears as well as reduces torque the motor has to apply and thus heat produced in the motor.

I see you use the term heat creep differently. I understand now.

Posted : 07/06/2019 8:36 pm
Vojtěch
(@vojtech-3)
Honorable Member
Posted by: bobstro

Prusa released updated R3 extruder parts last year that improved airflow for hotend cooling and a revised part cooling fan. If your part cooling fan is at an angle, you already have that installed. I've casually looked for fan replacements but haven't found any that provide significant improvements.

I have had success with the Sanyo SanAce B52 109BC24GC7-1  fan for improved part cooling. It's a drop-in replacement mechanically, but requires minor changes to the wiring because it's a 24V fan (I can explain if there is interest) and also a small firmware patch, because the firmware cannot handle a 7000rpm fan without changes. I also have a NMB 04010SS-24N-AT-00 ready as an upgrade for extruder cooling, but since my room never goes above 25°C, I haven't replaced the Noctua yet. Both the fans are high quality japanese fans and very quiet when operated at low RPM, but also able to deliver a strong airflow at full 24V.

Posted : 07/06/2019 8:45 pm
bobstro
(@bobstro)
Illustrious Member
Posted by: Vojtěch

This is a separate cause, though, and here an increased air flow wouldn't help indeed. 

OK guys, I suspect we're talking past each other. Going to push back on both of you this time... The heat in this specific example originates in the extruder motor. Yes, it travels down the shaft to the Bondtech gears, contributing to softening. However:

  1. Adding heat to an already heated environment is not going to help. The warm shaft is one of several possible contributing factors to heat where it shouldn't be above the hot end, adding to the mystery of warm weather printing that we encounter here in summer months. (I also  suspect filament softening in the cold end due to loss of efficiency in the hot end heatsink contributes to back pressure, further adding to the extruder motor workload.)
  2. The heat originates in the extruder stepper motor. Some folks add passive heat sinks to their extruder stepper motors, even if the ambient temps are within the stepper motor's rated range. Air flow is going to improve the performance of passive heat sinks. Improved passive heat sink performance will cool the extruder stepper motor. A cooled extruder stepper motor will generate less heat on the shaft. (Even without a passive heatsink, I'd still expect this to apply, albeit to a smaller degree.) I don't claim to know everything, but I spent enough time doing PC upgrades to know that ambient temps impact heat sink performance in a big way.
  3. Pulling away heat (improving cool air circulation) from any contributing source will help in an air cooled system.

So yes, improving circulation won't cool the extruder stepper motor shaft directly, but I think it's a mistake to just say "improved cool air circulation won't help", especially since there's no guarantee heat on the extruder stepper motor shaft is the, or even one, cause.

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 : 08/06/2019 4:42 am
bobstro
(@bobstro)
Illustrious Member
Posted by: Vojtěch

[...] I have had success with the Sanyo SanAce B52 109BC24GC7-1  fan for improved part cooling. It's a drop-in replacement mechanically, but requires minor changes to the wiring because it's a 24V fan (I can explain if there is interest) and also a small firmware patch

Ah bummer. I'm OK with the voltage conversion bit, but am really trying hard to stay away from customizing firmware. I was bitten too many times in the past doing that, so like to stay with mainstream release firmware wherever possible, at least so long as this is my only 3D printer.

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 : 08/06/2019 4:44 am
bobstro
(@bobstro)
Illustrious Member
Posted by: Vojtěch

So far I have only seen the term heat-creep used to refer to heating of the cold-end through the heatbreak and through heat carried to the cold end by the filament during retracts. The filament will then soften in the cold zone and cause a jam. To combat this, the increased airflow will help.

There are formal definitions, and then there are the terms in common use. As we approach summer, expect to see a lot of griping about "heat creep" that intermingle any source of unwanted heat that contributes to filament feed issues. I suspect most people trying to fight a problem aren't going to care what it's called, they just want help.

The E motor overhating and heating up the Bondtech gears as cause of jams seems to also be very real according to user reports, and usually results in grinding of the softened filament. And I do agree that a better extruder fan will not help here at all. [...]

Here again, users come here for help, so the finer technical distinctions aren't their primary concern (nor mine, frankly). The Prusa R3 parts included revamped airflow specifically for improved circulation around the E3D hot end heatsink. Issues in this area can contribute to back pressure which can add to the extruder stepper motor workload, contributing to... you get the idea.

I like to look at the printer as a whole for troubleshooting rather than specific sub-assemblies. Many of the bits & pieces that make up a Prusa interact with other pieces in interesting ways when something is amiss. So high ambient temps can contribute to filament softening in the cold end, contributing to extruder motor workload. Excessively high speeds exceed MVS of the hotend, adding to back pressure, contributing to extruder motor workload. Same symptom, different causes. (The stepped heatbreak is another contributor.)

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 : 08/06/2019 4:54 am
Vojtěch
(@vojtech-3)
Honorable Member
Posted by: bobstro
Posted by: Vojtěch

[...] I have had success with the Sanyo SanAce B52 109BC24GC7-1  fan for improved part cooling. It's a drop-in replacement mechanically, but requires minor changes to the wiring because it's a 24V fan (I can explain if there is interest) and also a small firmware patch

Ah bummer. I'm OK with the voltage conversion bit, but am really trying hard to stay away from customizing firmware. I was bitten too many times in the past doing that, so like to stay with mainstream release firmware wherever possible, at least so long as this is my only 3D printer.

The voltage conversion is trivial, simply connecting the red fan wire to pin 1 of J19, the Pi Zero connector. That'll feed the fan 24V, and since the Einsy uses low-side switching, the fan switching will work. Then, a Schottky diode or a small MOSFET needs to be added to the yellow wire to prevent flow of current from the fan to the RPM sense input. Without the diode or transistor, the fan spins slowly even when off.

And then comes the bummer. To overcome the disadvantages of low-side switching, the firmware is written specifically for the 5V fan, and has a built in limit on how fast it's willing to believe the fan spins. The limit is around 5000 rpm. If the fan spins faster, the firmware will not recognize it and report fan failure. The limit needs to be raised, because the Sanyo fan spins at 7000rpm at full speed. That is the only firmware modification required.

I'm not sure if it'd be possible to get that limit raised in the official firmware. Simply because it's not a fix that'd be needed for stock hardware.

Posted : 08/06/2019 7:59 am
Peter M
(@peter-m)
Prominent Member

I had also problems with filament getting stuck(from the beginning of the printer), and filament going outside the extruder to the side, and filament stuck in the nozzle. A few months back in time i got it stuck several times. And i have the mk3 version not the S, i have the new fan mounted to the latest MK3 cad.

What is the problem i do not know. Maybe wrong building the nozzle or heatbreak ??????

I rebuild the nozzle and heatbreak, to :

Heatbreak to a original e3d heatbreak, not prusa.(prusa they say , have a wider heatbreake),

Search for how to assembly the heatbreak and nozzle, on prusa website and youtube, so i am 100% do it the wright way.

Also a extra fan on top of the extruder, to blow upwards, and cool the extruder(helps a lot), i am in a enclosure, with pla i leave the door open.

Also a extra fan, especially for summer, i can blow inside the enclosure, if needed, only for pla.

I already have a extra power suply for extra fans, for a filter cleaner fan inside encloser, extruder fan and enclosure fan.

 

At the moment everything works very good.

I had one problem, a roll of pla the extruder starts clicking, but with 20 degrees higher it went away, other filament works okay.

 

What was the problem in the pass.........................???????????????//

I somebody knows, tell me.

At the moment it works very good, 24.00 our a day printing for weeks now.

Posted : 08/06/2019 9:07 am
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