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Temperature gone mad!  

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Alpha
(@alpha)
Estimable Member
Temperature gone mad!

Folks - printed 1000s of hours fine with my Mk3, but just gone mental overnight!

Temperatures running away up to 300C as it prints and then beeping madly as temp maxed.

Where should I start to fix this? Clearly something has broken!

Thanks in advance

Posted : 06/06/2019 3:29 pm
Vojtěch
(@vojtech-3)
Honorable Member
RE: Temperature gone mad!

If the hot end really is 300 °C hot, then the heater MOSFET on the Einsy board died and the board likely needs replacing. If it's just showing 300 °C, then the thermistor wires or the thermistor itself is shorted.

This post was modified 2 years ago by Vojtěch
Posted : 06/06/2019 5:13 pm
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(@)
Illustrious Member
RE: Temperature gone mad!

Katie - it's probably premature to say some has shorted, or what has broken ... not enough information. 

 

Is this a one time occurrence? Or is it now running temps up to 300c on every print attempt? Or is it running up to 300c just with the printer being turned on?

Posted : 06/06/2019 5:25 pm
Alpha
(@alpha)
Estimable Member
Topic starter answered:
RE: Temperature gone mad!

Symptoms are I can print fine, it seems to hold the temperature fine and then becomes more erratic with temperature readings shooting up and down. It then runs away randomly after a few layers print to shoot up to 300C.

I've done 3 attempts now and symptoms appear the same, so it appears consistent in occurrence

It also is jumping around in temperature much more erratically than usual - ie jumping from 215 to 190 in one go and then back up etc

I think it is getting that hot as I can smell the PLA burning slightly - literally nothing changed, no fiddling etc, just perfect prints and then not!

 

This post was modified 2 years ago by Alpha
Posted : 06/06/2019 6:31 pm
Alpha
(@alpha)
Estimable Member
Topic starter answered:
RE: Temperature gone mad!

Yes, doing a test print at the moment and normally if I set it at 215, it'd vary probably 3-4C max throughout the whole print, whereas I'm getting large variances - eg 30C +/-.  It's failed with thermal runaway

Dodgy thermistor maybe?

This post was modified 2 years ago by Alpha
Posted : 06/06/2019 6:38 pm
Vojtěch
(@vojtech-3)
Honorable Member
RE: Temperature gone mad!
Posted by: katie.o

Yes, doing a test print at the moment and normally if I set it at 215, it'd vary probably 3-4C max throughout the whole print, whereas I'm getting large variances - eg 30C +/-.  It's failed with thermal runaway

Dodgy thermistor maybe?

Yes, that seems to be the most likely explanation. The actual temperature can't change  quickly, so it looke like a measurement error.

This post was modified 2 years ago 2 times by Vojtěch
Posted : 06/06/2019 6:54 pm
Chocki
(@chocki)
Prominent Member
RE: Temperature gone mad!

Just out of interest, would the first few layers by any chance have the fan off?

Your cooling fan hasn't developed a droop and is now blowing directly onto the heater block?

 

Also no printing, just set a temperature and use the LCD to move the extruder up and down. left and right and see if the temperature remains stable, if not, you most likely have a broken wire.

This post was modified 2 years ago by Chocki
Normal people believe that if it ain’t broke, don’t fix it. Engineers believe that if it ain’t broke, it doesn’t have enough features yet....
Posted : 06/06/2019 7:28 pm
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(@)
Illustrious Member
RE: Temperature gone mad!

Katie - what you are describing is a failed thermistor.  They crack inside (for lack of a simpler term) and as they heat the cracks expand and cause increasingly erratic values. 

ps: Chocki has a point: does the variation happen if the extruder isn't moving?    If you still see jumps, then a broken thermistor wire is possible. But still means you'll need a new thermistor.

This post was modified 2 years ago 2 times by --
Posted : 06/06/2019 7:44 pm
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(@)
Illustrious Member
RE: Temperature gone mad!

Man -- I just can't type today!  Tried fixing the wording twice ... lol ... and I was even wearing my glasses.

If the temperature is NOT stable when the extruder is NOT moving... the wires may be the issue.  

This post was modified 2 years ago by --
Posted : 06/06/2019 7:52 pm
Chocki
(@chocki)
Prominent Member
RE: Temperature gone mad!

Tim, are you sure you haven't 😋 been at the cooking sherry 🍷 

What you have written isn't correct

If the temperature is NOT stable when the extruder is NOT moving... the wires may be the issue. 

ergo temperature jumping around when extruder stationary so wires not moving.....

I think you mean, if stationary and temperature fluctuating erratically, then thermistor suspect, if the jumping only starts when the extruder is moving, then wiring suspect. I know, it's late (and that sherry is working .... 🤭  we wont tell anyone).

Normal people believe that if it ain’t broke, don’t fix it. Engineers believe that if it ain’t broke, it doesn’t have enough features yet....
Posted : 06/06/2019 8:48 pm
Alpha
(@alpha)
Estimable Member
Topic starter answered:
RE: Temperature gone mad!

Heh, thank you all for both your sober and not so sober responses..... 😉

Ten minutes to swap out the thermistor and heater cartridge - had spare of both so thought I might as well. 

Printing two hours later still fine...!

Suspect it was the thermistor by the symptoms, although the heater cartridge wires were exposed at the 90 degree turn into the block, so reckon they were on the way out.

Don't know why they don't sell thermistors /heater cartridges with a 90 degree turn at end to reduce stress, but hey!

Gonna order some backups from e3d for future, can I check:

1) Prusa MK3 uses a 40w 24v heater cartridge?

2) E3d offering PT100 as better option than standard thermistor - is this worth doing and will it work with MK3? It suggests in blurb it doesn't with all printers

https://e3d-online.com/pt100-temperature-sensor

Posted : 06/06/2019 9:07 pm
Vojtěch
(@vojtech-3)
Honorable Member
RE: Temperature gone mad!
Posted by: katie.o

Ten minutes to swap out the thermistor and heater cartridge - had spare of both so thought I might as well.  Printing two hours later still fine...!

Glad that worked. 🙂

Suspect it was the thermistor by the symptoms, although the heater cartridge wires were exposed at the 90 degree turn into the block, so reckon they were on the way out.

A broken heater can't easily cause the temperature to go up above what's set on the printer, so it was likely innocent and the blame goes to the thermistor which was shorting somewhere, probably internally in the cartridge, when heated.

Gonna order some backups from e3d for future, can I check:

1) Prusa MK3 uses a 40w 24v heater cartridge?

Yes. However, there are Prusa-specific parts in the E3D shop, with the correct cable lengths and correct connectors. So unless you like to solder and crimp, get those. Or you can get them from the Prusa shop, too.

2) E3d offering PT100 as better option than standard thermistor - is this worth doing and will it work with MK3? It suggests in blurb it doesn't with all printers

https://e3d-online.com/pt100-temperature-sensor

Unless you intend to print at high temperatures (above 300 °C)  the PT100 is not worth the hassle. While it can be connected to the Einsy, it's not straightforward and doesn't improve resolution 'normal' temperatures (up to 285 °C).  So if you don't need to print exotic materials like PEI or PEEK, the normal thermistor is the better choice. Also, for printing at high temperatures, you'd need many more upgrades, like the copper heater block because aluminum softens too much above 300 °C, or a titanium heatbreak and a stronger hot-end fan.

Posted : 07/06/2019 5:53 am
Alpha
(@alpha)
Estimable Member
Topic starter answered:
RE: Temperature gone mad!

Excellent advice - thanks vojtech-p6!

Re heater cartridge - totally agree re symptoms, just saw the exposed wires on the heater cartridge and thought I might as well replace it whilst I had the 'bonnet open' so to speak...!

Re Prusa parts - great tip, didn't spot those - that'll make life easier (although a bit of solder and crimping is good for the soul IMO... 😉 )

Re PT100 - perfect, will keep it simple then! 

Thanks again for advice!

Posted : 07/06/2019 4:42 pm
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(@)
Illustrious Member
RE: Temperature gone mad!
Posted by: chocki

Tim, are you sure you haven't 😋 been at the cooking sherry 🍷 

 

Yesterday was just a bad Tim-on-Computer day.   I wish I had alcohol as an excuse.  Maybe I'll blame a Dyslexia spike.  After a bit I came back through, reread what I had written to correct the prior post and found I had messed it up, too.  So I quit for the day.  

Posted : 07/06/2019 5:18 pm
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