Thermal Runaway

I have been having problems with thermal runaways. It usually happens when the extruder is heating, but sometimes when the bed is heating. It happens usually during the first few minutes, but sometimes after a few hours. i have tried replacing the power supply. I also tried pid tuning. Anyone have any ideas what could cause this?

Attached is a screenshot of a short print.

Do you have RAMPS with those brown thin fuses?


They need to be cooled or they might overheat and cut power to bed or nozzle.
You might even want to replace them with standard blade fuses.

Yes it does have those fuses. If I do replace them which ones should I get?

Thanks for your reply.

I just took a temperature reading on the fuses using an infra red thermometer. They are 90-96F after printing for 4 hours.

Edited 1 time(s). Last edit at 09/07/2016 03:20AM by fusa.

In your firmware, there's a place where you can put in a delay before it checks to see if the temperature moved enough in that length of time. Up that time and you won't have problems anymore. I'm not where I can tell you the actual spot but you should be able to find it. Essentially you are giving it more time to be sure the temp is changing.

---

Folger Tech 2020 i3 and FT-5 as well as modified JGAurora A5 with direct drive E3D/Titan. All running the BLTOUCH.
Great kits. Having fun and running the heck out of them.
Running Marlin 1.1.0 RC8 on the i3 and FT5. Custom firmware on A5.
Folger Tech Wiki board >[folgertech.wikia.com]

After looking more closely at the extruder, I realized the heater block was against the heat sink, and the nozzle too far out. I fixed this and replaced the thermistor. The past 3 prints have had no problems, very little fluctuation in temperature.

This has been fixed but maybe others come here and have the same problem.

1.) Check that the thermistor is not cooled be any fan.
2.) Check that the thermistor is not damaged.
3.) Check in the firmware the timers for thermal runaway. Like tjnamtiw said: up the time. Default is 20sec. 30-40 sec is also fine.

---

Blog: Capotexl
Filament Factory - How to build your own cheap filament extruder
Frankenstein Laser Engraver
Make the world a better place

Quote
ianmcmill
This has been fixed but maybe others come here and have the same problem.

1.) Check that the thermistor is not cooled be any fan.
2.) Check that the thermistor is not damaged.
3.) Check in the firmware the timers for thermal runaway. Like tjnamtiw said: up the time. Default is 20sec. 30-40 sec is also fine.

In configuration.h, 'Residence time' is the time that the hot end has as a grace period to stay within a set range or get back there. Hysteresis is that range. In other words, if you set residence time to 10 seconds and hysteresis to 4 degrees, that means that when your temperature drops or rises more than 4 degrees from the set point, you have 10 seconds for it to get back into range. And once it is within range for 10 seconds, the computer will know it's OK to proceed.

I had this problem when my thermistor came partially out of the hot end and was being cooled by an A/C vent nearby. I also had the problem when the heated bed was situated directly under the hot end and the hot end fan was blowing on the heated bed thermistor area. That one was a head scratcher for a while.

Edited 1 time(s). Last edit at 09/27/2016 03:48PM by tjnamtiw.

---

Folger Tech 2020 i3 and FT-5 as well as modified JGAurora A5 with direct drive E3D/Titan. All running the BLTOUCH.
Great kits. Having fun and running the heck out of them.
Running Marlin 1.1.0 RC8 on the i3 and FT5. Custom firmware on A5.
Folger Tech Wiki board >[folgertech.wikia.com]