Testing safety features (MK3/MK3S)

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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 how to debug them.

All of these features must be tested during a running print.  You can use models from the bundled SD card, for instance, the Batman or Prusa logo.

Filament sensor 

How to test the filament sensor

1. First, you must make sure that the Filament sensor is turned on. You can check that in the LCD Menu - Settings - Fil. sensor ON/OFF.
2. Let the print run for 5-10 minutes, then simply cut the filament and wait until the sensor triggers it.
3. The printer will then ask you to press the knob and unload the filament.
4. After that, simply load a new filament into the extruder. Either by pressing the knob or if you have the autoload turned on, it will be done automatically. 
5. If changed correctly. Select YES. If you did not load the filament, select Filament not load or if the color is not clear select 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 extreme light conditions.
3. For more information, see IR Filament Sensor (MK2.5S, MK3S/+, MK3.5/S).

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 the 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 automatically. 

The printer is not recognizing hits and skips 

1. Double-check that you are running the printer in the 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. If the crash detection does not work, you can visit Layer shifting for more information. (Layer shifting has a lot in common with none working crash detection.) 

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 all the time. Best practice is to have a power strip with an 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 the 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. The actual firmware version running on your printer can be found in the LCD menu under Support -> Firmware. The latest version can be always found at our Downloads page.
   2. Check your Z-axis assembly. Any extra friction might prevent the proper Z movement.