Skip to content
How Do You Test a Thermal Runaway?

How Do You Test a Thermal Runaway?

One of the most clear-cut and consistent ways of checking the safety and temperature of the printer is through the thermal runaway feature. Sometimes, the printers, often from popular brands, have this thermal feature automatically enabled so that during use, when the temperature rises, the thermal runaway can be controlled.

The main job of the thermistor usually installed in the printer is to continuously check and prevent the temperature of the printer from going too high. In an event where the thermistor is damaged or loosened, the thermal runaway comes to the rescue.

The importance of reading the temperature of the printer is that sometimes the temperature becomes too hot or too cold without you realizing it. In any of these events, the printer continues to try to maintain the desired temperature without assistance. If the thermistor is broken and the thermal runaway is not triggered, it becomes a very dangerous situation for the printer to keep the required temperature afloat.

One of the problems that can be encountered is the heater block melting due to the inability of the thermal runaway to be triggered, and this continuous melting of the heater block can start a fire when it becomes overloaded.

In this article, we are going to discuss:

  • The steps that show you how to test the thermal runaway of your printer to ensure safety
  • How to learn how to check the consistency of the thermal runaway when your printer is misbehaving.

Let's get right into it.

What Is a Thermal Runaway?


The thermal runaway is a safety feature that is triggered when the temperature of the printer is unstable. This feature automatically stops every printing action on the machine once it senses a dangerous situation or fluctuating temperature. Thanks to the Thai feature, 3D printing can be done with ease as thermal runaway protection is triggered in the face of danger. As we pointed out earlier when the thermistor of the printer is damaged or out of place, the thermal runaway takes full control, as long as it is automatically enabled.

What Happens When the Printer Shows a Thermal Runaway Error?

When the thermal runaway refuses to function, there might have been an underlying cause, and in such an event, the printer displays the error message "thermal runaway error".

When you see this instead of the thermal runaway protection being activated, it clearly shows that the printer's temperature is not stable and the thermistor is out of place. 

The next step to take is to ensure that the thermal runaway is available to take over if it has not already been triggered. Some printer brands do not have this automatic function in place for the thermal runaway feature and it needs to be conducted manually.

If that is the case with your printer, you have to immediately trigger the function of the thermal runaway manually. In an event where the thermal runaway still does not become active, you would need to test if it is even in place or already damaged.

How to Test a Thermal Runaway

For checking the functionality of the thermal runaway in your printer, these are the 4 main steps below to guide your process.

Step 1: Warm up the nozzle

The nozzle of the printer plays an important role in the printing process, and it must have a set temperature as well. When testing the thermal runaway, the first step is to ensure that the nozzle is preheated to the required temperature.

Step 2: Blow on the nozzle to cool it down

If the temperature of the heater block is very high, you can make use of a cooling or blower system to reduce the heat generated. This process might be slow as it does not yield a fast result, but with consistency, the temperature begins to drop and the temperature is returned to its normal form. 

Step 3: Thermal protection is activated

When the cooling system or air compressor is used, the thermal protection system is immediately triggered, and you can be sure that the system will be back to its normal functionality gradually. In a situation where the temperature is still constantly dropping, it reveals that the thermal protection system has not been enabled or is not working at all.

Step 4: Make sure your firmware is up to date

If the thermal runaway is not triggered, it is better to stop all operations for the sake of safety. After that, the firmware of the printer needs to be updated to ensure that the thermal runaway of the printer regains its ability to function properly. To update the firmware, you can check with the company that makes the printer or check online for how to activate and update the firmware. 

What Causes the Overheating That Triggers Thermal Runaway?

There are quite a number of things that could cause overheating in a 3D printing machine, and these things are meant to trigger the functionality of the thermal runaway feature.

If the heat generated from the heater block is not controlled, it can lead to a lot of hazardous situations by causing the system and its components, especially the plastics, to melt, which can, in turn, result in a huge fire outbreak when not managed. Let's look at some of the causes of the overheating of the printer that is supposed to trigger the functionality of the thermal runaway.

  • Damaged thermistor: In a situation where the thermistor is faulty, removed, or not in good connection with the internal heating block, it immediately causes a fluctuation in the temperature, leading to the overheating of the printer. This is largely because the temperature is not able to be regulated at this point. 
  • Improper wire connections: Another cause of overheating which can trigger the functionality of the thermal runaway is improper wiring, which can be due to faulty connections in the printer. If the wires that need to be carefully connected in the internal compartment of the printer are mishandled, it can lead to fluctuating temperatures, thereby causing overheating.
  • Removal of the heater cartridge: the displacement of the heater cartridge or if it was removed due to a previous repair would definitely disrupt the function of the printer, and it can also cause differences in temperature rate, leading to overheating.

In an event where one or all of the above situations occur if the thermistor is broken or out of place, it is the duty of the thermal runaway feature to step in. If this is not done, the printer will continue to overheat, resulting in the melting of the heater block and, eventually, a fire explosion if not stopped immediately.

This is why the testing of the thermal runaway protection system is necessary, and because you are dealing with a machine that might malfunction at any time, putting a safety feature in place is advised. One such safety feature is the presence of a fire extinguisher in the event of a fire outbreak and a cooling system should the need arise where you need to cool the printer before it begins functioning again.

The Advantages of Thermal Runaway Testing

Testing for a thermal runaway is critical, and ignoring it can result in a lot of damage and dangerous situations. are some of the benefits of testing the functionality of the thermal runaway.

  1. Testing the thermal runaway allows it to operate as a warning signal to prevent damage and even to the point of causing the fire. If the system is well maintained, it makes it easier to detect faults, which can be repaired on time to avoid further damage.
  2. As a preventive measure, testing the thermal runaway often ensures that hazardous issues are prevented from escalating. The thermal runaway protects the storage devices and batteries of the printer from damage if it is easily triggered at the right time.
  3. The thermal runaway is used to control the temperature of the printer if the thermistor is faulty or not in place. If the thermal runaway had not been triggered, this might have occurred as a result of its malfunctioning or not being put in the position to be automatically triggered at the time of need.
  4. The thermal runaway protection system also ensures that the printing process is not altered as it can carry on with its process while the thermal runaway is kicked into action. 


Testing of the thermal runaway protection to ensure it is functioning is very much advised as it can help to prevent a lot of issues and damage. Safety is very important, and in an event where the thermistor and thermal runaway do not function, ensure you have safety measures in place. Make sure the printer is not in the exit way and that there is the presence of a fire extinguisher and a smoke detector. 

The use of the thermal runaway feature has made 3D printing easy and is also useful in controlling the rise or fall of the temperature to ensure safety. When your next printer encounters a heating process, you'll know how to check for and trigger thermal runaway.


Previous article How to Fix Under Extrusion- What Causes Under Extrusion on Your 3d Prints and How to Fix Them

Leave a comment

Comments must be approved before appearing

* Required fields

Join us as seller