Prusa Mini Extrusion Troubleshooting

A couple of weeks ago I needed to print a case for my new Raspberry Pi 5 and SSD. I loaded up a nice yellow, sliced the file, and clicked print. I always watch the first layer go down, and this was as far as I got. The first layer was awful. It was inconsistent and in some places, there was no layer at all.

I tried a couple of times. Testing the bed was level, clean, and Z offset all seemed fine. The next item on the list was the nozzle and extruder. After unloading the filament, there was some evidence of debris in the extruder.

Extruder

The extruder is responsible for pushing the filament through the nozzle, this means that it’s an area of heavy wear. With debris in the extruder, it loses its efficiency at pushing and retracting the filament the correct difference. This ultimately affects the amount of filament that’s deposited on the build plate and could easily explain the print quality issues I was seeing. I won’t go through the process of explaining how to disassemble the extruder and perform maintenance, as Prusa has fantastic documentation¹. This is one of the reasons I purchased a Prusa printer in the first place.

Nozzle

The next check was to ensure that the nozzle wasn’t clogged. This is done by purging the filament and inspecting the extruded filament as it drops from the nozzle. It should drop vertically with no curling up on itself. On first inspection, it appeared acceptable, but acceptable isn’t enough, I felt that a cold-pull² should be carried out just to ensure that there is no debris partially clogging the nozzle. As thought, there was some debris in the nozzle, so wasn’t a waste of time.

Completing the extruder and nozzle maintenance. It made sense to give the printer a once-over while out of action. All signs were promising.

Fine Tuning and Results

After performing any form of maintenance the printer should always be reconfigured and calibrated. This is a case of ensuring that all the axes are squared³ against each other, the belts have the correct tension⁴, and the Z offset is correct. The latter is done last, as every change will require it to be carried out once again.

Having completed the checks, and general maintenance there was only one thing left to do. I loaded some yellow silk PLA. Then tried to print the case I attempted before the work was carried out. The first layer went down perfectly and the print was a success.