<p>I had a similar problem with an Anet A8 once. The problem was, that the thermistor wasn't mounted right <strong>in</strong> the heat block, so the air flow cooled it while the print head was moving. You can check, whether this is a problem at your printer.</p>

CC BY-SA 4.0
2020-10-29T14:57:47.690Z
According to the OP's Octoprint screenshot, it was the target temp that dropped, not just the achieved temp, so I don't think this is a plausible explanation.
R.. GitHub STOP HELPING ICE
CC BY-SA 4.0
2020-10-29T20:31:10.917Z
@R..GitHubSTOPHELPINGICE As I mentioned, after a while I manually lowered the target temp.
Daniël van den Berg
CC BY-SA 4.0
2020-10-29T20:32:19.860Z
I will definitely check my thermistor.
Daniël van den Berg
CC BY-SA 4.0
2020-10-29T14:44:43.010Z
2020-10-29T15:02:19.193Z
2020-10-29T15:02:19.193Z
Felix Teschke
<p>I'm printing basically a large flat square pane. This goes fine for 3 layers, after which the temperature suddenly drops by about ten degrees. After a while, my printer goes into thermal runaway protection.</p>
<p>I restarted my print, and as soon as the temperature drops, I pause the print. I wait for it to go up again, and resume. It starts dropping again, so I decide to see about continuing this part at 200 degrees (which worked quite fine, so I think I'll stick at 200 for now.)</p>
<p><a href="https://i.sstatic.net/0hG7j.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/0hG7j.png" alt="Temperature suddenly drops to 200" /></a></p>
<p>I have tested running the printer at 210 and turning on the fan, thinking maybe it's simply related to that. That does not give a thermal runaway, and a drop of 2 degrees max. My assumption is that it's the PID.</p>
<p>How do I fix this?</p>
<p>My printer is a heavily modified Anet a8, running Marlin.</p>

CC BY-SA 4.0
2020-10-29T14:12:47.867Z
Can you measure the hot-end temperature independent of the sensor to tell if you are really getting the temperature drop then thermal runaway, or is this a problem with the sensor?
Perry Webb
CC BY-SA 4.0
2020-10-29T14:15:22.997Z
I can not, don't have tools for that. But considering that it rises again as soon as I pause, I'm assuming I am really getting a temperature drop. I highly doubt there is any actual thermal runaway, considering that the temperature does remain stable at 200. So, without any tools to definitively confirm, that rules out an actual runaway for me.
Daniël van den Berg
CC BY-SA 4.0
2020-10-29T14:17:54.920Z
Did you test the 210 °C with full part cooling test near the bed or in the air/at certain Z height.
0scar
CC BY-SA 4.0
2020-10-29T14:46:09.533Z
I did, by pausing the print. This keeps the fan on, and the print head at the same height.
Daniël van den Berg
CC BY-SA 4.0
2020-10-29T14:58:35.367Z
Are you sure the slicer didn't insert temperature reduction commands?
R.. GitHub STOP HELPING ICE
CC BY-SA 4.0
2020-10-29T16:11:16.117Z
You can get Infrared Laser Thermometers as low as $25 to measure the hot-end temperature.  That would allow to compare with the sensor.
Perry Webb
CC BY-SA 4.0
2020-10-29T20:33:58.937Z
@R..GitHubSTOPHELPINGICE Yes. The problematic drop is the one around -18 min, not the one around -8 min. The one around -8 min (the drop in target) was manual.

And I'd assume that any conceivable temperature reduction command would show up in the light red line, right?
Daniël van den Berg
<temperature><thermal-runaway>
Drop in temperature after couple layers
Daniël van den Berg
# Drop in temperature after couple layers

(Asked by: username_0 on 2020-10-29)

I'm printing basically a large flat square pane. This goes fine for 3 layers, after which the temperature suddenly drops by about ten degrees. After a while, my printer goes into thermal runaway protection.

I restarted my print, and as soon as the temperature drops, I pause the print. I wait for it to go up again, and resume. It starts dropping again, so I decide to see about continuing this part at 200 degrees (which worked quite fine, so I think I'll stick at 200 for now.)

[![Temperature suddenly drops to 200](https://i.sstatic.net/0hG7j.png)](https://i.sstatic.net/0hG7j.png)

I have tested running the printer at 210 and turning on the fan, thinking maybe it's simply related to that. That does not give a thermal runaway, and a drop of 2 degrees max. My assumption is that it's the PID.

How do I fix this?

My printer is a heavily modified Anet a8, running Marlin.

**Tags:** temperature, thermal-runaway

> **Comments:**
> **username_1**: Can you measure the hot-end temperature independent of the sensor to tell if you are really getting the temperature drop then thermal runaway, or is this a problem with the sensor?  
> **username_0**: I can not, don't have tools for that. But considering that it rises again as soon as I pause, I'm assuming I am really getting a temperature drop. I highly doubt there is any actual thermal runaway, considering that the temperature does remain stable at 200. So, without any tools to definitively confirm, that rules out an actual runaway for me.  
> **username_2**: Did you test the 210 °C with full part cooling test near the bed or in the air/at certain Z height.  
> **username_0**: I did, by pausing the print. This keeps the fan on, and the print head at the same height.  
> **username_3**: Are you sure the slicer didn't insert temperature reduction commands?  
> **username_1**: You can get Infrared Laser Thermometers as low as $25 to measure the hot-end temperature.  That would allow to compare with the sensor.  
> **username_0**: @username_3 Yes. The problematic drop is the one around -18 min, not the one around -8 min. The one around -8 min (the drop in target) was manual.  And I'd assume that any conceivable temperature reduction command would show up in the light red line, right?  

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## 1 answers

### Answer by username_4 on 2020-10-29. Score: 1

I had a similar problem with an Anet A8 once. The problem was, that the thermistor wasn't mounted right **in** the heat block, so the air flow cooled it while the print head was moving. You can check, whether this is a problem at your printer.

> **Comments:**
> **username_3**: According to the OP's Octoprint screenshot, it was the target temp that dropped, not just the achieved temp, so I don't think this is a plausible explanation.  
> **username_0**: @username_3 As I mentioned, after a while I manually lowered the target temp.  
> **username_0**: I will definitely check my thermistor.  

---

