Thermal Runaway with 3.0.6?  

Re: Thermal Runaway with 3.0.6?

Bad thermistor (or more likely its cables or connector) shows up as sudden jumps in temperature values. In one second you have 200C and in next secod you have 230C or 14C (when completely ripped off).
Insufficent power of heating element shows as rather slow gradual temperature drop.

Re: Thermal Runaway with 3.0.6?

Bad thermistor (or more likely its cables or connector) shows up as sudden jumps in temperature values. In one second you have 200C and in next secod you have 230C or 14C (when completely ripped off).
Insufficent power of heating element shows as rather slow gradual temperature drop.

Excellent, today I will go back home and test to see how the temperature varies. If it does not vary I will still be concerned printing a large print and wasting filament only to have it fail 10 hours into the print like last time.

Re: Thermal Runaway with 3.0.6?

I am getting gradual variations from 257 to 250. Temperature is not stable and this is just in preheat phase before printing. The printer has difficuly reaching correct temperature and staying there. When printing starts and filament flows the same behaviour persists withe temperature varying from 251 to 257. I just started a large print to see if I get the same error again.

Re: Thermal Runaway with 3.0.6?

Hello,

I'm also having problems with thermal runaway. My setup is as follows:

Stock MK2
Official E3D thermal silicone sock
Hatchbox silver PLA
215C first layer
200C second layer
200 micron height

The print will fail between the second and fourth layer, every time. I notice that the temp jumps around quite a bit once the fan kicks on. Like 15C swings within seconds. Is that possible from a physics perspective? Is this a bad thermistor? Can I check or do anything before contacting support?

Thanks very much for any help.

Re: Thermal Runaway with 3.0.6?

Ryan

Have a look here: http://help.prusa3d.com/mk2-electronics/thermal-runaway-and-temperature-drops in particular the thermistor connector issue.

Peter

Re: Thermal Runaway with 3.0.6?

Peter,

That graph in the thermistor connector section looks exactly like what's happening to me. Thanks very much for posting. I'll look at the connector as soon as I get home from work today. To be honest, it looked like the flimsiest part on the printer even out of the box, so it's not surprising that may be the issue.

-Ryan

Re: Thermal Runaway with 3.0.6?

Ryan

Have a look here: http://help.prusa3d.com/mk2-electronics/thermal-runaway-and-temperature-drops in particular the thermistor connector issue.

That's very interesting. As is this, from the help docs:
the small thermistor wires got broken inside the connector where it is crimped, you best bet is to cut away the connector all together, splice the wires and solder them together. Our manufacturing process is being adjusted (11 Oct 2016) so new printers will come like this.

Does that mean that the new connector isn't performing and the wires will now be connected in-line? That's too bad, as it seems that the connector was a great idea.

Re: Thermal Runaway with 3.0.6?

So how did you confirm it was was a bad thermistor? I want to gather as much information as possible before I contact support.

Thanks
this forum (in czech). Then I have called the support and very pleasant lady told me they are sending new extruder.

Re: Thermal Runaway with 3.0.6?

Try to put the thermal paste into the hole of termistor(the same kind you use for uP in your PC).
Temperature drops are caused most likely by flowing air into the hole of extruder sensor, while sensor is not attached onto the surface of the ALU block. People that have thermistor well attached inside the hole will not see the issue. It seems it has nothing to do with resistance drops on connector. This helped on mine so far. Try it.

Re: Thermal Runaway with 3.0.6?

Try to put the thermal paste into the hole of termistor(the same kind you use for uP in your PC).

Not a great idea. Many thermal pastes go rock hard at these temperatures and when a thermistor change is required, a new heat block will also be needed.

Peter

Re: Thermal Runaway with 3.0.6?

So today I got same issue with thermal runaway. Paste was not long term solution. All connections checked. I wonder if the cooling fan is not too much directed onto the hotend. Or the final solution is to change the heat element?
Thanks

Re: Thermal Runaway with 3.0.6?

Is the temperature behaviour like this?

then it is termistor error and you chould change extruder.

Re: Thermal Runaway with 3.0.6?

So today I got same issue with thermal runaway. Paste was not long term solution. All connections checked. I wonder if the cooling fan is not too much directed onto the hotend. Or the final solution is to change the heat element?
Thanks

PC thermal paste is no solution at all. Did you bother to read the specification of your thermal paste?

http://help.prusa3d.com/mk2-electronics/thermal-runaway-and-temperature-drops#_ga=1.122873995.1841328043.1474356652

If you can solder you should replace the connector of the thermistor as mentioned in the linked troubleshooting advice above.

Re: Thermal Runaway with 3.0.6?

It was similar, but after todays print the temperature went down completely. I found out, that one of the termistor wires got damaget. I made also video

and test

I hope this helps finally.
In my opinion, it is very important to tight all wires carefully and/or put some tape or shrink tube onto the wires, because it broke, where there is also bending during printing process.

and Simon, there is no connector on the sensor in my case.

Re: Thermal Runaway with 3.0.6?

I got two of these after lots of good prints, wasn't monitoring the temps, so it could easily be a different matter. It's weird to me to call this a 'thermal runaway' problem, it's actually the opposite of one, a result of problems caused by thermal runaway protection gone awry.

I'm posting to relay something that happened a bit ago, right in the middle of a long, 20+ hour print, I saw something sitting in the middle of the print, which had multiple levels, so it was on a surface lower than the currently printing level. I couldn't really tell what it was, but it looked suspiciously like a set screw. It was printing fine, so I let it continue, when print was done, it was indeed a set screw, the one for the thermistor. That isn't something I had ever touched. The print did not evidence any change of appearance between before and after the set screw fell out, and I had many good prints before, so I just put it back in and there was no noticeable degradation, or enhancement, in the prints afterwards. Until now if this is related.