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I am new to 3D printing and having a strange issue I don't understand and would love some help with. I have an Ender 3 Pro and when I use the settings 200 °C & 60 °C it prints fine. However, I want to change the bed to 55 °C as the bottom layers are melting a bit. I changed this in Cura to 200 °C & 55 °C and get a thermal runaway after 20 minutes or so. I hit resume and the same thing after about 20 minutes, however, the times vary.

I did a PID using the same set temps 200 °C & 55 °C and still thermal runaway. So I changed all the numbers back to 200 °C & 60 °C and ran a PID on this original temps and ran perfect (except for the first layers melting a bit)

The odd part is the bed temp holds fine when adjusted to 55 °C, it's the hot end that starts to drop a few degrees (5 degrees) which triggers the runaway. Is this a fan issue (currently at 100%)? Before I started changing things I wanted to ask here.

Looking forward to your feedback. BTW I am able to change the PID right on the machine and have no experience altering G-code or the knowledge but am willing to try?

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  • $\begingroup$ I assume you're getting a thermal runaway error. Is there any evidence of the printer actually starting into thermal runaway? $\endgroup$
    – Perry Webb
    Commented May 10, 2022 at 19:23
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    $\begingroup$ Also what is the model of your 3D printer? Your temperatures sound like you're printing PLA. $\endgroup$
    – Perry Webb
    Commented May 10, 2022 at 19:25
  • $\begingroup$ yes running hatchbox pla black. ender 3 pro is all i know. Yes its a thermal runaway. I have been watching it and seeing the hot end temp drop. $\endgroup$
    – MJH12
    Commented May 11, 2022 at 0:01
  • $\begingroup$ i thought a thermal runaway was when things get way too hot? $\endgroup$
    – dandavis
    Commented May 11, 2022 at 22:13
  • $\begingroup$ The bottom layers experience elephant's foot, not melting. PLA only melts at ~180 °C $\endgroup$
    – Trish
    Commented Feb 3 at 19:12

2 Answers 2

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Sounds like a thermostat problem, 60 degrees shouldn't be melting the first layers with PLA.

I would try manually checking the temperatures and move forwards from whatever results I got from that.

If the heats were fine, then I'd be inclined to return it as a faulty unit if it's under warranty.

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  • $\begingroup$ I have changed the thermistor multiple times and definetly not. Im thinking its a G-code issue. $\endgroup$
    – MJH12
    Commented May 12, 2022 at 11:21
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    $\begingroup$ How could it be gcode? The gcode just sets the temperature right at the start if you're not doing fancy modifications to it. Have you tried flashing the firmware? I was going to suggest that but unsure what it would do to the warranty status $\endgroup$
    – Kilisi
    Commented May 12, 2022 at 13:35
  • $\begingroup$ I bought this unopened from a third party. I have not flashed the firmware. I will look into that. I have printed 4 10+ hour prints all beautifully since I started this thread. All at 200/60. so strange that changing the temp down 5 degrees on bed drops the hotend. What do you think about it being a fan issue? Maybe all both bed and hotend fans are firing at the same time? $\endgroup$
    – MJH12
    Commented May 12, 2022 at 14:02
  • $\begingroup$ I don't know sorry, but the firmware controls the fans. I have never had a fan issue so have no experience with that. The fact that the issue is intermittent could be a capacitor issue, but thats a board problem. If your board is playing up then you need professional help unless you're an electrician $\endgroup$
    – Kilisi
    Commented May 12, 2022 at 14:08
  • $\begingroup$ I still think there is something wrong with your heat readings, I have done 2, 3 and 4 day prints that don't have any melting bottom layers at 60 degrees bed $\endgroup$
    – Kilisi
    Commented May 13, 2022 at 8:05
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Could be a bad thermistor, could just need a pid tune. I would start with pid tuning it, if that doesn’t work I would swap it for a new one. Don’t forget to pid tune the new one if you end up going that route.

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    $\begingroup$ The OP states that they have already changed the thermistor (multiple times) in this comment $\endgroup$
    – Greenonline
    Commented Sep 6, 2023 at 16:06

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