Fracktal printers come with an inbuilt feature to avoid accidents by overheating of the nozzle or heater cartridge. Due to an issue with the printer, if the heater cartridge heats beyond a certain temperature, it can lead to melting of the hot end and also fire hazards. So the built-in programming in the firmware of the printer has features that make sure that uncontrolled heating of the heater cartridge does not happen.
How will the heater cartridge will over overheat to Dangerous levels?
The temperature control in 3D printers is done using input from the thermistor. The thermistor continuously senses the temperature and will pass it to the control board. Sometimes, when the thermistor fails to give a correct reading, it may show that the nozzle has not reached the required temperature, and in turn, the heater goes on supplying heat, which raises the temperature to dangerous levels, causing accidents.
How does thermal runaway protection help to avoid this?
As nicely explained by a Stack Exchange user named Oscar: “Thermal runaway protection is basically self-explanatory; it is protection against the temperature getting out of control. Essentially, the firmware checks whether the measured output of the thermistor (What is a thermistor? A thermistor is basically a temperature sensor; it is an electrical component (more specific: a resistor) that has a large reduction of its resistance when heated; it is frequently used for measurement and control as you can link the resistance to the temperature via a table or a curve) is within an expected range for a certain target value within a certain time frame when heating the hotend or the heated bed. E.g., when you request the hotend or heated bed to a certain temperature, the heater elements are being scheduled/switched on to increase the temperature. If the temperature increase as a result of scheduling the hotend or heated bed is not met in time (settings in the firmware configuration), the printer will halt, and heating of the heater elements will stop. The printer needs to be reset after such a failure. What triggers TRP? Common problems that trigger the thermal runaway protection are: a faulty thermistor, an incorrectly placed thermistor (e.g., not making good enough contact with the heater block), including falling out a loose heater cartridge, including falling out faulty connectors, faulty or partially broken wires, basically, anything that interrupts either heating or the measurement of the signal.”
Other causes for thermal runaway:
In short, thermal runaway is triggered when the temperature reading and projected temperature values mismatch. So sometimes the printer gives this error when there is a connectivity issue or a bad heater cartridge as well. If the cartridge is faulty, the printer will not reach the required temperature, and the controller board will give a thermal error in such a case.
Troubleshooting checklist:
If a thermal runaway error occurs, these can be the reasons.
1. Faulty MOSFET in the control board.
2. FFC is damaged and is not giving temperature to the controller board.
3. Thermistor damaged or loose connection
4. Heater cartridge damaged or loose connection.
5. Faulty PCBs.
