MK3 safety features - how to test them

Updated 1 week ago ​by Tomáš Chvalina

Our brand new Original Prusa i3 MK3 comes with lots of new safety features. That makes printing a lot more reliable and safe. In this article, we will showcase how to properly test all of them and what are the most common sources of any problems.

In order to test all of the features, use some of the models from the SD card. All of these features must be tested during printing with instructions described below.

Filament sensor 

How to test the filament sensor

  1. Make sure that you have this feature turned on. You can do that in LCD - Settings - Fil. sensor [on/off]
  2. Simply cut the filament during any of your prints and wait until sensor triggers it.
  3. The printer will then ask you to press the knob and unload the filament. You can repeat this process. 
  4. After that, simply load a new filament into the extruder. Either by pressing the knob or if you have the autoload feature on, it will be done automatically. 
  5. If changed correctly. Press [Yes], if you did not load the filament [Filament not load] or if the color is not clear [Color not clear].

False sensor reading and debugging 

  1. Check if the sensor is positioned correctly and connectors are properly seated.
  2. Make sure that there is no Dust on the sensor or there are not extreme light conditions.
  3. You can find more information in the Filament sensor article.

Skipped steps and layer detection 

How to test the "crash" detection 

  1. Make sure that your printer is running in the normal mode. You can check that in LCD - Settings - Mode [Normal/ Stealth and that crash detection is enabled in  LCD - Settings - Crash det[on/off]
  2. Pinch the smooth rods close to the extruder, which will result in stopping it while printing.
  3. Do not push the extruder. As this does not simulate a real printing scenario.
  4. If done properly, the extruder will auto home and restore printing. 

Printer is not recognizing hits and skips 

  1. Double check that you are running the printer in normal mode. 
  2. Make sure that your belt and pulley are tightened. Would any of them be loose, it may cause the belt to jump over the pulley or the pulley to spin around the motor shaft. 
  3. More information can be found in Layer shifting

Power panic

How to test power panic

  1. Do not use the power switch. That does not trigger power panic.
  2. You can pull the power cord from the wall. However, it may not work perfectly. Best practice is to have a power strip with [on/off] switch. 
  3. So simply switch off the power strip in the middle of your print. 
  4. The printer will then raise the nozzle and once the power is back, it will heat up and restore printing without user interaction. 
  5. If the power goes off for a longer period of time and nozzle/bed is cool. The printer will wait for you and ask if you want to restore printing. 

Power panic did not trigger or work 

  1. If it did not trigger while unplugging the power cord (which we do not recommend). It may have been caused by arcing produced by the cord. 
  2. Nozzle did not rise far enough. 
    1. Make sure that you are running the newest firmware version. Actual firmware version running on your printer can be found in the LCD menu - support - Firmware [version]. The latest version can be always found at
    2. Check your Z axis assembly. Any extra friction might prevent proper Z movement.

In case of any troubles. Please do not hesitate to contact us at

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