Hot End Problems  

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DrHotwing
(@drhotwing)
Active Member

Hi there, I'm looking for some help here before I pull the remaining hair that I have left out 🙂 

I recently had some issues with clogging that I never had before (I've printed many successful prints, even with a .25 nozzle with never a clog).

I began troubleshooting by taking apart my extruder assembly and checking carefully all components of the hot end. The result was filament clogged up in the heat block. I proceeded to let the unassembled heat block hang while removing the nozzle and heating it up to 285c. I used a thin wire rod to carefully clean and remove the clog. After reassembling everything and running the full calibration again I got the filament to flow again with the first layer calibration. I began to print my project once again, it ran until half completed (a long detailed 26 hour print), which was perfect, then once again it clogged again. The temp was at a consistent 205 (I always use PLA). I took the nozzle off once again and tried to pull out my clog. In doing this, and while at 285c I noticed that the filament in the hot end was tacky and sticky. At this point I thought the thermistor was producing the wrong temp so I replaced the entire E3d with a new genuine E3d hot end kit since my hot end looked a bit beat up anyway.

After properly installing everything I went to the wizard again to calibrate everything again. Everything passed but going through the first layer test the filament won't come out at all and although the hot end is hot the PLA filament is tacky inside again (at 285c I would expect the filament to be running out and liquified). I have tried all kinds of tests to get it to flow but no success. I even tried to stick a piece of filament directly into the hot end block but the filament just gets sticky (it doesn't liquidity at all). I also tried 5 different PLA spools, mostly newer, and one was brand new right out of the plastic thinking it might be the filament.

I spent a lot of time learning the entire machine, and how it works but I can't seem to figure this out since the machine is relatively new and has a brand new hot end kit on it as well.

My printer is the Prusa mk3s with mmu2s. both with the latest firmware.

Any help would be great as I would love to get back to printing.

Thank you

Jeff

 

Posted : 23/03/2021 8:20 pm
Clarmrrsn
(@clarmrrsn)
Honorable Member

@drhotwing

As you have replaced the hot end did you run PID adjustment to calibrate it?

Prusa Knowledge Base | PID tuning (prusa3d.com)

Also, what E3D hot end did you fit, was it like for like?

This post was modified 2 months ago 3 times by Clarmrrsn
Tank you very much!...
Posted : 23/03/2021 8:24 pm
DrHotwing
(@drhotwing)
Active Member

@clarmrrsn

I replaced my E3D V6 hotend with the exact same. I was told from E3D that it was a 'drop in' replacement. I followed the instructions exactly.

Also, the temperature on the screen stays pretty spot on and doesn't fluctuate much at all

 

This post was modified 2 months ago by DrHotwing
Posted : 23/03/2021 8:30 pm
Clarmrrsn
(@clarmrrsn)
Honorable Member

Did you run PID?

Tank you very much!...
Posted : 23/03/2021 8:32 pm
DrHotwing
(@drhotwing)
Active Member

@clarmrrsn

No, not yet

 

Posted : 23/03/2021 8:34 pm
Clarmrrsn
(@clarmrrsn)
Honorable Member

OK, I would suggest running it as is a different heater/hotend and Thermistor.

What PLA are you using, and what temps are you running it at?

Tank you very much!...
Posted : 23/03/2021 8:35 pm
karl-herbert
(@karl-herbert)
Illustrious Member

@drhotwing

I would go through the points on the Prusa help pages step by step:

https://help.prusa3d.com/en/article/clogged-nozzle-hotend-mk3s-mk2-5s_2008

Statt zu klagen, dass wir nicht alles haben, was wir wollen, sollten wir lieber dankbar sein, dass wir nicht alles bekommen, was wir verdienen....
Posted : 23/03/2021 8:39 pm
DrHotwing
(@drhotwing)
Active Member

@clarmrrsn

OK I ran the PID calibration. Tried the first layer calibration and still no filament extruding.

I've tried Hatchbox, Prusament, and Amolen filaments. I normally run my PLA at 205 but I've tried all different temps. 

What's troubling me here is that even having the temp at 285c the filament won't melt. It just gets sticky and deforms a bit. This is placing it directly into the hot end

I know that I installed everything properly and have triple checked everything, checking right from the install book just to be safe 

 

Posted : 23/03/2021 9:06 pm
DrHotwing
(@drhotwing)
Active Member

@karl-herbert

I've done each item (and many more) and nothing worked.

Like I mentioned, with the hotend hanging (heatsink and nozzle removed) I cranked the temp to 285c and took a small piece of filament and stuck it directly into the nozzle hole and it didn't even melt, the filament just got stick and soft but didn't ooze. The temp stayed at 285 and (without touching it) felt hot but didn't melt the PLA.

This seems very odd as i've been printing for a long time even before getting the mk3s and I never encountered a problem like this.

I had this printer printing very detailed pieces and it never clogged like this

 

Posted : 23/03/2021 9:14 pm
3Delight
(@3delight)
Moderator

The thing that glares at me is you say PLA isn't melting when you set the hot-end temp to 285c.  Have you tried:

1) Reflashing the firmware for the MK3?

2) Checked the wiring for the hot-end sensor AND heating cartridge?

If those don't help then I would be suspicious that one of them is defective.  However, you say you've replaced them so that would suggest it could be a problem with the EINSY board.  How long have you had the printer?

Posted : 23/03/2021 9:22 pm
karl-herbert
(@karl-herbert)
Illustrious Member

@drhotwing

The melting temperature for PLA is around 160 degrees C.
If this does not melt at a theoretical nozzle temperature of 285 degrees C., something is wrong with the temperature management.
Heating cartridge, thermistor or Einsyboard.

Statt zu klagen, dass wir nicht alles haben, was wir wollen, sollten wir lieber dankbar sein, dass wir nicht alles bekommen, was wir verdienen....
Posted : 23/03/2021 9:50 pm
hli
 hli
(@hli)
Trusted Member

285°C might be too hot - PLA might start to degrade at this temperature (it should melt at 180°C already), and might get stuck immediately. Does it extrude when you push it manually (with the extruder door open so they gears do not interfere)? Are you sure it actually goes down into the extruder and is not stuck somewhere before (e.g. in the short PTFE tube)?

Does the hotend cooling fan run properly? (Thats important to avoid any heat creep)

Posted : 23/03/2021 10:39 pm
DrHotwing
(@drhotwing)
Active Member
Posted by: @3delight

The thing that glares at me is you say PLA isn't melting when you set the hot-end temp to 285c.  Have you tried:

1) Reflashing the firmware for the MK3?

2) Checked the wiring for the hot-end sensor AND heating cartridge?

If those don't help then I would be suspicious that one of them is defective.  However, you say you've replaced them so that would suggest it could be a problem with the EINSY board.  How long have you had the printer?

1) Reflashing the firmware for the MK3? - Yes. Reflashed it today again.

2) Checked the wiring for the hot-end sensor AND heating cartridge? Yes to both. It passes the diag tests as well. Everything appears perfect except for the hot end not letting the filament pass through

I purchased the printer direct from Prusa in September 2020

 

Posted : 23/03/2021 11:34 pm
DrHotwing
(@drhotwing)
Active Member

@hli

Yes, I tried taking the nozzle out and the P.I.N.D.A sensor trigger door, I then pushed the filament through the top of the extruder and it went right through with no issues.

The heat fan comes on, and stays on, from around 50c until it cools back down to below 50c.

 

Posted : 23/03/2021 11:51 pm
3Delight
(@3delight)
Moderator
Posted by: @drhotwing

@hli

Yes, I tried taking the nozzle out and the P.I.N.D.A sensor trigger door, I then pushed the filament through the top of the extruder and it went right through with no issues.

The heat fan comes on, and stays on, from around 50c until it cools back down to below 50c.

 

Posted by: @drhotwing

1) Reflashing the firmware for the MK3? - Yes. Reflashed it today again.

2) Checked the wiring for the hot-end sensor AND heating cartridge? Yes to both. It passes the diag tests as well. Everything appears perfect except for the hot end not letting the filament pass through

I purchased the printer direct from Prusa in September 2020

 

So it boils down to:

a) There is no clogging in the extruder.  The whole pathway is clear of blockages (I assume you checked the nozzle itself).

b) The LCD is showing the right temperature that you set.  Are you able to confirm the hot-end AND nozzle are getting to that temp using some form of meter?

c) The PLA you are using is OK.

Two more questions:

1) Have you tried disconnecting the MMU2 to see if that is causing the problem?

2) What happens if you set it to the correct PLA temp (200c-210c)?

3) Have you contacted PRUSA support through the chat feature? If not I would recommend doing so as it is still within the 12 month warranty period.

Also, lastly, can you post some photos of the extruder from 3 or 4 angles?

This post was modified 2 months ago 2 times by 3Delight
Posted : 23/03/2021 11:55 pm
DrHotwing
(@drhotwing)
Active Member

OK, so I heated to 220c, once at 220c I placed a meat thermometer directly onto the nozzle and the highest I can get the thermometer is 170c. I then disconnected my brand new E3D hotend and placed my original on and retested the same (220c on screen). I placed the thermometer onto the nozzle and let it sit there for a while, again the highest reading on the thermometer I get is 170c.

The next test I did was take the nozzle out and crank the temp up to 285c. I placed the meat thermometer directly into the nozzle opening, up against the inside of the hot block and once again nothing higher than 170c.

This is exactly the same result with both my new genuine E3D V6 hotend and my original E3D hotend that came with my printer.

This is bizarre...

Regards,

Jeff

 

Posted : 24/03/2021 12:56 am
3Delight
(@3delight)
Moderator

So the heater cartridge is only getting up to 170c, that means either:

1) The heater cartridge is faulty and not getting hot enough (unlikely as the LCD would show 170c or

2) The Thermister is reading the temperature as way over what it is

2) The EINSY Board is producing the wrong current/volts or reading the thermistor wrongly.

 

Now, if the heater is only getting to 170c then it must be either be the thermistor cartridge in the hot-end or the EINSY.  The way I am looking at it is:

a) The Firmware tells the EINSY to activate the heater cartridge, then:

b) The firmware monitors the input from the thermistor via the EINSY until it reads your set temp (200c or 285c)

c) The Firmware starts using PWM to keep the heater at the set temp.

OK, so lets assume the heater and thermistor cartridges are working OK (as you have tried 2 of each of them), then it must be the EINSY or the firmware.  You've re-flashed the firmware so we can rule that out at this stage.  So that just leaves the EINSY.

My advice is to get on to PRUSA Support via the chat feature on the EShop homepage and see if you can get a replacement sent under the warranty, if that fails then you can buy one in the EShop.

 

I know it's not what you want to hear, but I can't see what else it can be.

This post was modified 2 months ago by 3Delight
Posted : 24/03/2021 1:59 am
hli
 hli
(@hli)
Trusted Member

What I meant with manual extrusion: heat the nozzle up (even 170°C should be enough), and feed filament manually through the hotend. (Just like you would when doing a cold pull as described by Prusa). You need to relieve the extruder so you can push the filament manually.
With 170°C th filament should go through, even though you will need to push quite a bit.
(Btw: are you sure your thermometer does actually read more than 170°C when only its tip is heatened?)

Maybe you can separate the hotend from the extruder and then heat it up (though be careful when touching the hotend). That way you can also better determine how far into the hotend the blocking is (by measuring the length of filament you can push into it)

Posted : 24/03/2021 7:07 am
DrHotwing
(@drhotwing)
Active Member

Thank you all for your help in this matter. I ended up contacting Prusa support (which by the way is amazing) and they are working with me to resolve my issue.

 

Posted : 24/03/2021 2:37 pm
3Delight
(@3delight)
Moderator
Posted by: @drhotwing

Thank you all for your help in this matter. I ended up contacting Prusa support (which by the way is amazing) and they are working with me to resolve my issue.

 

Hope all goes well, and please come back and tell us what the final solution is!

Posted : 24/03/2021 10:08 pm
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