Direct granules extruder V5.5: PET-G gearbox

The video about the Prusa MK4 conversion, part 6.

Extruder V5.5

Direct Granule Printer V5.4: Abmessungen

Figure 1:
The extruder tube is identical to the previous version 5.4, only the gearbox has been changed.

Gearbox from PET-G

Direct Granule Printer V5.5: Parts gearbox

Figure 2:
After the metal gear of Extruder V5.4 became increasingly loud during operation, indicating wear, I decided to print my own gear out of plastic.

Direct Granule Printer V5.5: Pinion and gear ring

Figure 3:
In addition to the advantage that worn parts are easy to replace, the reduction ratio can also be freely selected. In the first version, the pinion on the stepper motor has 11 teeth (fewer teeth are not possible due to the diameter of the stepper motor shaft) and the ring has 32 teeth. This results in a reduction ratio of 2.91 to 1.

Direct Granule Printer V5.5: Ball bearing type 6001

Figure 4:
The ball bearing absorbs the forces from the extruder. I use a cheap radial bearing that can't absorb excessive axial forces. Future tests will show whether the type 6001 I use, with an outer diameter of 28 mm, is sufficiently dimensioned.

Direct Granule Printer V5.5: Cpupling auger screw

Figure 5:
The extruder screw with its M8 nut engages in a slightly larger hexagon hole on the gear shaft.

Figure 6:
The gear shaft also comes from the 3D printer and is reinforced with 3mm screws, since a pure plastic shaft with a diameter of 12mm would not be able to withstand the resulting torque.

Direct Granule Printer V5.5: assembled gearbox

Figure 7:
The finished gearbox including Nema 17 stepper motor and extruder screw weighs 422g and is only slightly larger than the metal gearbox.

Auger screw

Figure 8:
An M8 nut is hard-soldered to the extruder screw with a diameter of 4.5mm and the resulting screw head is filed slightly round.

Figure 9:
To ensure the M8 nut is properly centered, I use an M4 nut as a guide. I drill halfway through the M8 nut with an 8mm drill bit to allow the M4 nut to fit.

Figure 10:
Alternatively, the head of an M8 screw can be drilled through the center with a 3.2mm drill and soldered.

Download

All 3D files, the Open SCAD file and the dimensional drawing are part of the download package.

Print examples

Direct Granule Printer V5.5: Example track link

Figure 11:
track link:
Dimensions: 27x25x12mm

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