HOTEND THERMAL RUNAWAY ( drop temperature )  

RE: HOTEND THERMAL RUNAWAY ( drop temperature )

Posted by: @gianluca

Hi ,

i am new here and also a newbie with 3D printer . I had a problem during my last prints .

 

Usually I used PLA , I change to PETG ( original Prusa wire ) and first prints was really good ! 🙂

 

During my last prints I had problem with suddenly stops ( after some hours or even after some minutes ) and I can't complete any prints now .

All the jobs STOPS with error "HOTEND THERMAL RUNAWAY" .

Attached 2 snapshot of OctoPrint where you can see whats happen during my print. Seem the the heating of the extruder stop to work during the printing process.

 

I checked with multimeter the hardware ( thermistors and heater ) and the Ohm values are ok .

What is VERY strange it's "sometimes" also preheating on the printer is NOT WORKING . ( bed is heating , extruder is NOT heating , also unplugging the raspberry octoprint USB connection  ) . After some period and restart the heating restart to work correctly .

Any one have any idea of what is the problem ?

Many thanks

Gianluca

 

 

 

Thermal runaway almost always indicates a thermistor defect. The thermistor does not necessarily have to be defective. The cause of the malfunction can be a defective cable (loose contact) or a loose or corroded plug contact.
Try connecting the multimeter to the thermistor lines and moving the extruder back and forth. If the value of the display changes rapidly, you have a problem with the connecting leads and know that you have to replace them.

RE: HOTEND THERMAL RUNAWAY ( drop temperature )

@karl-herbert

Hi Karl ,

thank you for your quick and detailed answer .

Tomorrow I will made the test that you suggest BUT my feeling is that there is another problem .

2 clues :

- If you look the octoprint temperature graph you see that the temperature goes progressively down some minutes before the stop , this seem to indicate that the power of the heater is missing . The print STOP because the temperature is really going down .

- I checked using the preheating function on the M3KS display . Sometimes seem that the heating is NOT working . The bed temperature raise UP , the hotend reamain stable at same temperature ( let me say ... ambient temperature ). I deconnected the heater , checked it with ohm and was OK ( 14.8 Ω ) . I tried with multimeter to see the power supply of it and was 0V ( NO POWER ) !

Digging on the forum I discover this topic and seem exactly my problem  🙁

I am not a electronics technician like @pekote so , did you know how I can contact directly PRUSA support to check if the Einsy RAMBo (MK3S) have some problem ?

Many thanks

Gianluca

RE: HOTEND THERMAL RUNAWAY ( drop temperature )

This points to a problem in the PS wiring, not necessarily a fault of the Einsy. Removing the power fault wires - if it resolves the heating issue, will isolate the issue to the PS or Einsy.

RE: HOTEND THERMAL RUNAWAY ( drop temperature )

@tim-m30

Hi Tim ,

thanks , I made the test , detached the  " PSU power panic " from Einsy .

and tried to heat up but the hotend temperaure don't raise up : 

See also attached LOG LOG Manual PreHeating

After this test I also tried  LCD Menu -> Calibration -> Selftest  and now also the BED is not heating UP .

What you think ?

Many thanks

Gianluca

RE: HOTEND THERMAL RUNAWAY ( drop temperature )

It would appear the Einsy is the issue; or, a broken wire in the extruder harness that is intermittent (as stress failures usually are). A broken extruder heater wire is difficult to troubleshoot, but when the heater temps drop during a print - do NOT move the extruder - leave it where it is. Power cycle the printer and try heating the nozzle only. If it doesn't heat up, you've got a good chance a wire is broken. If you then home the printer, and try to heat, and it does heat - pretty good confirmation it's a bad a wire.

RE: HOTEND THERMAL RUNAWAY ( drop temperature )

@gianluca

Is the black/white powerpanic cable connected correctly? You may have to swap the connections.

RE: HOTEND THERMAL RUNAWAY ( drop temperature )

@karl-herbert

If PP power cable is reversed at one end, a diode on the PP board prevents damage and would keep it from doing anything nasty. If the PP signal cable were reversed, it'd pull AC_fault low all the time (if the mosfet reverse diodes are working).  I was looking for it to somehow be pulling down on the AC_fault line - with the wire disconnected, and no heat on both channels, low chance it was reversed, either.  Begs the question why an open collector circuit somehow helps lift the AC-fault signal tho. That one stumps me. Plus the fact removing the cable stops all heating makes me suspicious something else is going on, and probably impossible to diagnose remotely. Just too many variables.

But that said - plugging the power cable into the signal jack and power into the signal jack would do odd things. 

@gianluca

As Karl said, double check the power and signal cables are connecting to the correct jacks of the PP board.

Changing filament types will not cause a hard miswire ... but I am told miracles happen all the time.

RE: HOTEND THERMAL RUNAWAY ( drop temperature )

@tim-m30

Hi Tim and hi Karl ,

thank for your support .

Just for information I never dismount ( and mount ) my printer before this problem because  it's a fully assembled printer direct from PRUSA shop.

I connected again the PSU power panic cable , checked the right connections ( color cables in right places and order ) , all OK .

Started an a LCD Menu -> Calibration -> Selftest  :

- first BAD test ...  the printer suddenly RESTART during the FAN Test !

- tried again ( without moving any axis ) ... SELFTEST OK 

So I start to print looking the Graph on Octoprint , after some minutes the temperatures start to drop ... till the printer STOP in M112  .

here attached the video , the temperature on LCD screen was going down from 240°C to 205°C and after STOP in M112 .

I restart the printer , NOT MOVING THE HEAD , tried to warm agian and was NOT HEATING , another M112 .

After I restart again and WAS HEATING ...

I checked the wire connection near to the cardrige nad MAYBE we find the problem ( thanks to Tim ! )

if you look there is a "stripped"  wire .

I will order a new cardrige and I will change it ... crossfinger !!!

Keep you posted.

Many thanks

Gianluca

RE: HOTEND THERMAL RUNAWAY ( drop temperature )

Hi guys ,

I checked the procedure to change the heater and at step 28 there is a picture with the "strippe wire" exactly as mines.

So , BEFORE to fisically change the heater I decided to made a very quick test with the new heater ( checked , 15,0 Ω ) .

I only disconnect the old one and connected the new one on the terminals  to see if the heater start to warm in my hand.

What I see is :

- powered ON the PSU

- Prusa boot

- Boot finished and in some seconds ( I din't touch nothing ! ) reboot agian ( very strange ... )

- so , i decided to power OFF and ON again

- Boot OK

- Starting Pre-heating via the LCD screen ( LCD Menu -> PreHeat -> PET )

- Hotend was NOT heating , the heater in my hand was cold . Bed was also NOT heating . ALL the RED light on Einsy was OFF .

- Shutdown and power up again

- Boot OK

- Starting Pre-heating via the LCD screen ( LCD Menu -> PreHeat -> PET )

- Hotend NOT heating ( red light near the heater connector was OFF) , BED was heating ! ( red light on the einsy and near to the bed was ON )

- Shutdown and power up again

- Boot OK

- Starting Pre-heating via the LCD screen ( LCD Menu -> PreHeat -> PET )

- Hotend was HEATING ( red light near the heater connector was ON) , BED was heating  ( red light on the einsy and near to the bed was ON )

- Shutdown and power up again

- Boot OK

- Starting Pre-heating via the LCD screen ( LCD Menu -> PreHeat -> PET )

 - Hotend NOT heating ( red light near the heater connector was OFF) , BED was heating  ( red light on the einsy and near to the bed was ON )

so , in my personal opinon is a faulty Einsy , what you think ??? I need to contact the support ?

Many thanks

Gianluca

RE: HOTEND THERMAL RUNAWAY ( drop temperature )

I sent an email to technical support, now I'm waiting for their reply .

Keep you posted.

Gianluca

RE: HOTEND THERMAL RUNAWAY ( drop temperature )

@gia78

An inquiry by email may take some time. Faster would be the Prusachat. Just log in with your account and select the eshop. After a few seconds a chat window appears in the lower right corner.