Finix Extruder Post-processing & Assembly

Gather the parts listed on the Bill-of-Materials.


Extruder parts and tools


Use a knife (woodcarving knives work great for this) to get rid of any cruft left on the parts from the 3D-printing process.

NOTE: I judge the parts on their usefulness for the job they’ll perform. For me, they don’t have to be esthetically perfect. I won’t be entering them in an art show. We all have different views on esthetics, but for me, function is king.


Set of extruder components as produced by a 3D-printer


  • Drill a 2.0mm (or 5/64”) hole through the hole meant for the filament in the filament_leadin part.



filament_leadin part with hole bored to 2.0mm

NOTE: For the following set of drilling instructions, if you have both 2.5mm and 7/64” drills (recommended for creating M3 “locknuts” in 3D-printed plastic), I’ve found that when I need a strong fit—as with a setscrew that I want to hold against a shaft really tightly—I open the printed hole with the 2.5mm drill. If the screw doesn’t need that tight a fit, I follow the 2.5mm with a 7/64” bit. Both serve to create the effect of a locknut when an M3 bolt is screwed into the hole. The 2.5mm, being smaller, just gives a tighter fit

Drill 2.5mm (or 7/64”) holes (to be used as locknut-type fastenings):

  • in the bearing_capture part where the bearing is to be fastened,
  • also in the bearing_capture part where the release_lever “pull-out” screw will attach.
  • in one of the release-fulcrum features of the extruder_base (The other will be drilled out as a “pass-through.”)
  • in the four holes of the two_spring_retainer (clever name, huh?).

Drill the following as 3.5mm screw “pass-thru” holes.

  • The four motor-mount holes in the extruder_base,
  • The two motor-mount holes in each of the filament_leadin, filament_collar and mirrored_collar parts.
  • The four holes of the bearing_capture part that will be used to connect with the two_spring_retainer part.
  • The hole in the bearing_clasp.
  • The “other” release-fulcrum feature of the extruder_base.


As you go through the assembly steps, please read through each step completely. There are TIPs and NOTEs and CAUTIONs to make each step easier to complete.

  • If you’ll be using the tee_bracket to mount the extruder assembly to the Visible Robot’s ‘Z’ axis, with the NEMA17 motor shaft facing up, place the bracket onto the motor, lining up the four fastening boltholes of each.

NOTE: The picture below shows the tee being used as one to be mounted on the “3Struder platform.” The tee used to mount a single extruder to the Z-axis is the “finix_extruder_platform” as shown in thumbnail on the Finix Extruder bill-of-materials (BOM).


Motor and 3Struder tee: the “finix_extruder_tee_bracket”

NOTE: For the single extruder mount—the finix_extruder_ platform—the longer portion of the top should cover the motor, with the ovoid hole positioned over where the extruder will be placed. For the 3Struder mount, shown above, the “short” side of the “tee” should cover the motor. The “long” side (with the large off-center hole for the filament entry) will cover the extruder. As you’re positioning the bracket, think about the orientation of the motor wiring with respect to the extruder mounted on the ‘Z’ axis. Do you want the wiring to go up? Or to the right or left? Position the tee_bracket on the motor appropriately.

  • Slide the extruder_base over the shaft and the tee_bracket, again being careful as to its orientation.

NOTE: If you are building up a 3-extruder assembly, note that one of the three is a mirror image of the other two–a “left-handed” part. This one will be mounted as a mirror to the one it shares an axis with. (Either the robot’s ‘X’ or ‘Y’ axis, depending on the configuration you choose).


Setscrew started on hobbed drive (positioned at 5-o’clock for easy access later)


NOTE: The finix_extruder_base shown here is an earlier part, the photo taken during prototyping of the device. It has subsequently been strengthened to resist the fairly strong spring forces used to clench filament when in use.

  • Start the setscrew that comes with the Mk8 filament drive into it. It just needs to be started, not threaded all the way in.

TIP: If you orient the setscrew to the “5-o’clock” position, so that it’s easy to get to, aligning the bearing and Mk8 filament drive will be easier.

  • Put the hobbed Mk8 filament drive onto the motor shaft, with the hobbed portion toward the motor shaft’s end. (Setscrew closer to the face of the motor). The end closest to the hobbed features should be approximately 1/16” (~1.5mm) from the end of the motor shaft. ().
  • Insert the bearing_id_retainer into the bearing.


Bearing_id_retainer and 605_bearing_clasp sandwiching bearing

  • Place the bearing and retainer onto the bearing_capture part, with the bearing_id_retainer sandwiched between the bearing and the bearing_capture.


  • Now insert the circular feature of the bearing_clasp that fits the inside-diameter (ID) of the bearing into it, sandwiching the bearing between the bearing_capture and the bearing_clasp.



Sandwiching the sandwich

  • Fasten this subassembly with an M3 x 12 screw. The screw should not protrude from the bottom of the bearing_capture, as this might prevent the release from working properly. (By scraping against the extruder_base).

  • Temporarily, screw the base to the motor with a couple of M3 x 12 screws at opposite corners. This will keep the base stable while you put the release mechanism together. 

Temporary base tack-down

  • Insert the two springs into the recesses for them in the two_spring_retainer. The springs are 6mm outside diameter (OD) x 20mm long, 1.0mm wire.


Fitting springs into the two_spring_retainer

  • Position the subassembly completed earlier, above the features of the base that will be the release_lever’s fulcrum.
  • NOTE: The screw-head of the subassembly should face “up,” away from the motor.

image15_eppStaging the release_assembly

  • Keeping the two_spring_retainer and springs together, insert the loose ends of the springs into the recesses for them on the extruder_base.


image16_eppSetting the two_spring_retainer & springs into the  finix_extruder_base


CAUTION: As you screw in the bolts for the next operation, ensure that the bolts enter into the two_spring_retainer at a sufficient depth to avoid being pulled out by the force of the springs.

TIP: This operation can be made easier by slightly compressing the springs with a small clamp, if you have one.

  • While compressing the springs together, fasten the bearing_capture and two_spring_retainer with four M3 x 50 screws, putting some compression into the springs. The bearing surface should completely cover the groove containing the hobbed features of the Mk8 filament drive. (Next step)
  • You may find that the middle of the bearing and the hobbed portion of the Mk8 filament drive don’t line up as they should. If this is the case, remove the bolt that occludes the setscrew in the hobbed filament drive. Now, compressing the springs so that the bearing and filament drive separate, loosen the setscrew and using the hex (Allen) wrench as a lever, move the filament drive into alignment with the bearing. Tighten the setscrew. Replace the bolt you just removed.



  • The filament_leadin_bracket assembly is next. If you’re building a 3Struder rig, make sure of its orientation. (The two side-by-side—or opposite one-another, if you’re using a ‘T’ configuration—are mirror images of each other, so one filament enters one on the right, the other on the left).
  • Use two M3 x 30mm screws to fasten the filament_leadin_bracket to the motor. (Of course you’ll have to remove the screw you used to temporarily hold the base in place for the earlier operations).


  • Now take the E3D collar parts and strangle the neck of the E3D hot-end with them. (Pardon the bit of executioner humor there). The collar should fit tightly both around the neck and axially (up and down the neck).
“Strangling” the neck of the extruder
  • As you did with the filament_leadin_bracket, fasten the E3D hot-end and collars to the base with two M3 x 30mm screws.


E3D hotend and collar pieces fitted to the extruder

  • Finally, we come to the release_lever. Place it in between the “horns” of the base and fasten it with an M3 x 20mm screw. This screw provides the fulcrum for the release_lever.



Mounting the release lever

  • Use an M3 x 10 or 12mm bolt, screw it into the bearing_retainer. If the screw fits a bit loose, you can use a flat washer as a spacer, as I did here.


Completed assembly

  • Check that it works as expected by testing the grip and release with some filament.



Filament clenched

image26_eppFilament released

  • You’re DONE with the assembly!