The Purge Former And Brush (PFAB) unit (READ NOTES)

IMORTANT:

This PFAB unit is designed primarily to work with the following toolhead:
https://www.printables.com/model/1144586-ldo-apogee-toolhead-mod-for-installing-ke-hotend-o

You are free to adapt the PFAB to fit a standard height and depth toolhead if you wish. I haven't got a need for that though, as I designed this specifically for my machine, which uses an Ender3 KE nozzle.

I also have a filament cutter actuator which I will upload at some point that's designed to work with an LDO orbiter 2 equipped toolhead + a mirrored variant of the dragonburner cutter mech.

The PFAB (Purge Former And Brush unit) is a means of easily controlling purged materials when printing multi-coloured objects with a single extruder.

The main task this unit handles is preventing the purged material from becoming uncontrollable spaghetti that inevitably gets strewn all over the machine by balling it up as much as possible, then dumping it once the head moves from the PFAB unit.

I'd advise printing a catch bin that sits on the right hand 2020 extrusion of your machine for further containment of the purged filament.

Advisories for printing:

- I would strongly advise increasing your wall count on the PFAB body to make it as rigid as possible. This is so the nozzle is properly scrubbed by the brush after a filament change, as flex in the PFAB body can reduce the brush's ability to remove any stuck on material.

You can print this unit in any rigid filament. I printed mine in ABS but that's primarily because I have a heated enclosure and didn't want it to potentially warp with the heat. If you don't anticipate high heat, PLA will work perfectly for one of these arms.

Just be aware that you might want to also add a small layer of foil onto the forming arm's bucket to help with dropping the purged material.

As I primarily tested with ABS when iterating, I never ran into issues with filament sticking in the forming arm, but with stickier filaments like PETG or PLA, this is something to consider.

PARTS NEEDED TO COMPLETE THE PFAB:

M3x10 cap head screw: x2
M3x5mm cap head screw: 1
M3x25 shoulder screw: 1
Tension spring (0.5mm wire thickness, 4.1mm OD, 18mm free length): 1
Bambulab A1 silicone nozzle cleaner brush: 1 (cut in half)
PTFE tube (3mm ID, 4mm OD): 21mm length x1

ASSEMBLY AND INSTALL:

1: Cut 1x silicone nozzle cleaner in half, then stick it to the PFAB body in the rectangular recess

2: Slide a 21mm length of PTFE tube over the M3x25mm shoulder bolt, then screw this into the hole provided next to the brush on the PFAB body

NOTE: When installing the PTFE lined screw, try to leave it loose enough that the PTFE can spin easily on the screw. I've found this helps with getting a purged blob to break from the PFAB unit once the print head is moved away to clean the nozzle.

3: take 1x M3x10mm cap head screw and thread one side of the tension spring onto the screw.

4: Screw the tension spring onto the BACK of the forming arm with the provided screw hole (NOT the one which goes all the way through the forming arm!! that's for the hinge!)

5: Take the other M3x10mm cap head screw and use it to screw the forming arm onto the PFAB body. Try to get this tight enough that the arm doesn't wobble around much, but not so tight that the spring can't pull back on the forming arm and hold it against the limit tab on the PFAB body.

6: take the M3x5mm screw, thread it through the other end of the tension spring, then stretch it to the provided hole on the top of the PFAB body and screw in until secured.

See the provided image for a visual reference on how the completed PFAB unit should look.

INSTALLATION:

Note: It may be a smart idea to use a wrench on the inner V-slot wheel of the right hand X gantry plate to turn the eccentric nut so as to relieve the pressure on the V-slot wheels. This will make re-assembly much easier.

1: Remove the lower V-slot wheel bolt on the right hand side of the X gantry

2: seat the PFAB unit onto the X gantry and align the mounting hole with the bolt hole on the gantry plate

3: insert the bolt, then thread on one spacer, the V-slot wheel, then the other spacer in sequence

4: once the bolt is all the way through - re-install the nylock nut and tighten until secure.

Once the PFAB unit is installed, move the toolhead manually to check that the nozzle hits the brush and that the forming arm closes correctly before trialling a print.

Additionally, the PFAB arm should not hit the print bed at all when the nozzle is low enough to touch the print bed.

If you're wondering what the PTFE lined screw does by the way - it's there to help guide the purged material into the forming arm. The PTFE reduces the chances of the purged material sticking to the PFAB body and makes releasing the purge more reliable. The PFAB should work without it, but for the same reason I'd line the forming arm with foil, I would consider installing this screw.