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Thermal Runaway on PETG  

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prus-30
(@prus-30)
New Member
Thermal Runaway on PETG

My printer has turned into a paperweight after 10 prints, total, in its short life. Can you help:

  • Prusa i3Mk3s
  • Printing: a 25mm x 30mm x 30mm part
  • Prusa brand PETG filament
  • 240 Extruder temp
  • 95 bed temp
  • 18C room temp

About five minutes into printing, you can see the extruder temp start dropping like a stone (a question: if I can see the temp on the display, how come the printer can't see that same temp?). I successfully printed a single part earlier today, but now I can no longer print.

Is the Mk3 not capable of printing PETG? Is the thermistor a "wearing" part which needs to be swapped every 10 hours or something? The wires look OK, the fan seems OK (but who can tell since there are no helpful photos I've found which show "good" and "bad" fan setups), I ran the calibration at 245 and it says ok.

My error log, such as it is, on the printer shows a number of "power failures" but I don't know what that corresponds to, as I have found not online literature which suggests what that may be. Last print I tried shows two of them, no further details. To be clear, the power did not go out twice or ever, so I assume it refers to an internal issue of some sort?

I am not wealthy, at all, and the better part of $1,000 I spent on this feels like one of the stupidest decisions of my life. The technology is sold as being more advanced than this.

Please help.

Also noting the contact form on hemp.prusa3d.com does not work, which is encouraging.

Posted : 10/10/2019 5:50 am
Chocki
(@chocki)
Prominent Member
RE: Thermal Runaway on PETG

First of all check all electrical connections especially in the power supply, it will mean having to partially disassemble it, also check all the connections in the Einsy Rambo especially the power panic connection and the obvious one, can you try the printer in another socket in the house?, the amount of times in Europe where I have had a poor connection in old sockets makes me wonder how they continue to work?, some of these are over 30 years old and get everything plugged into them regularly. I just recently replaced some in my partners family home and the insides fell apart when I opened them up. It only takes a fraction of a second for the power panic to trigger, yet the printer appears to remain on.

This post was modified 4 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 : 10/10/2019 7:42 am
RH_Dreambox
(@rh_dreambox)
Prominent Member
RE: Thermal Runaway on PETG

If the temperature suddenly starts to drop when printing, it indicates that a cable for the heating element is damaged.
When the extruder is in a certain position, the cable is bent so much that a gap contact occurs.

Where the gap contact is located is difficult to say, but it can be under the extruder where the cable is attached with cable ties, or where the cables are connected to the electronics box.
Also make sure that there is no gap contact at the screw connections on the Einsy Rambo card.

Bear MK3 with Bondtech extruder

Posted : 10/10/2019 12:12 pm
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