Prusa i3 MK3 let's me change filament midway in a layer

Question

I was printing a 3D piece as usual when the printer suddenly asked me to unload the filament and load the filament mid-print. The change happens several times within the first layer already.

The only thing I recall being different from previous builds is that I set a material in Fusion 360. However, AFAIK, when I export the body to STL, there's no material information included. Also, it does not make sense to change the material within a single body if the whole body is the same material.

I only import this one STL object into PrusaSlicer.

I have tried:

• resetting the printer (press the physical X-button on the printer)
• restarting PrusaSlicer and recreating the slice from scratch
• looking for the M200 G-code (set filament diameter) - there is none
• looking for the M403 G-code (set filament type) - there is none
• looking for the M600 G-code (filament change procedure) - there is none
• looking for the M701 G-code (load filament) - there is none
• looking for the M702 G-code (unload filament) - there is none
• looking for the M705 G-code (eject filament) - there is none
• looking for the M706 G-code (cutfilament) - there is none
• defining a new printer profile based on the i3 MK3 system preset

I am using PrusaSlicer 2.3.0+win64. My printer is a Prusa i3 MK3. The printer firmware is 3.14.0-8066. I am printing via Octoprint 1.10.3.

The whole G-code is about 600kB and too much to paste here. If you have suggestions on what to look for, I will provide the information.

What can I do so that the printer prints a single body with a single filament without any filament changes during the print? (Basically like it did for the past 6 years)

Answer 1

Go to the printer menu and look at the print failure statistics. From the info screen that is Fail stats > Last print. You likely see that "Fil. runouts" is not 0.

The i3 MK3 has a filament sensor and can detect filament runouts. You likely ran into the procedure described at Prusa3D: Filament sensor MK3 (non-S). Check out the False sensor readings and debugging section there.

If you are sure that you don't have a filament runout situation, you can turn off the filament runout detection in Settings > Fil. sensor and set Fil. runout to Off. During a print, this option is in Tune > Fil. Sensor.

During the print you may want to monitor the filament runout sensor values at Support > Sensor info to see if the sensor is broken. The Yd value should go up continuously while printing and down when retracting.

In your particular case, you may want to upgrade to firmware 3.14.1, so that you are notified about filament runouts via the OctoPrint Web-UI.