Direct granules extruder V5.1 on a Prusa MK4

The video converting a Prusa MK4 to a granule printer, Part 2.

About Extruder V5.1

Direct Granule Extruder V5.1 on Prusa MK4

Figure 1:
The stumbling block in my development work on granule printing came in the form of a bag of PLA powder, which was obtained from pellets using an industrial grinder. This finer powder should be easier to process than the raw material I have previously obtained from failed prints, but that thought was wrong!
To err is human, to insist on errors is the devil - so it was necessary to face the facts and go back to the virtual drawing board in order to adapt the extruder to real physics. Sometimes this process has to be repeated several times, as can be seen in the mountain of reworked parts to the right of the printer.

Figure 2:
So the extruder tube was redesigned again. Version 5.1 is even shorter and the water cooling has been made more efficient.

Figure 3:
The extruder tube is tin-soldered to 1.5mm sheet steel, which on the one hand absorbs the torque better and on the other hand increases the cooling performance.

Figure 4:
The heat barrier now consists of a stainless steel tube with 7mm inner and 8mm outer diameter. The inner diameter of the extruder tube widens from the cold to the hot end, which reduces friction a little. At least with a 0.6mm nozzle the powder can now be printed reliably.

Figure 5:
Dimensions extruder tube

Rohmaterial

Figure 6:
PLA granules from recycled plastic

PLA raw material from industrial pellets

Figure 7:
PLA granules from grinded, industial pellets.

Download

The 3D files and the dimensional drawing of the extruder are available as download package.

Sample print

I deactivated the software refinements "pressure advance" and "input shaping" that the Prusa MK4 offers during the current tests. When it comes to printing tests, it's still important for me to see what the extruder can deliver, without interference from the printer firmware.

Figure 8:
Track link:
Layer height: 0.2mm
Print speed: 30mm/s
Nozzle: 0.6mm
Print time: 17min
Dimensions: 27x25x12mm
Material: PLA from industrial pellets

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