Bowden Speed Loader for Prusa XL and CORE One and similar for loading filament

(Be sure to check out the remixes for some great optional parts!)

I've had this concept in mind for a while, but finally got around to doing the work to make it a reality. This uses a bondtech style gear set to push the filament, similar to a Prusa Mk2/Mk3 extruder. Along with a battery, a reed switch, and a mid-RPM gearmotor, it can push or pull rigid filament through a bowden/PTFE tube with ease and quickness. One user has even tested TPU successfully!

To use, just line up the filament with the oblique teeth of the gears and clamp down on it. It doesn't matter much how the motor is wired. If it pulls when you want it to push, just flip it over (rotate on long axis). You might need to apply a little extra pressure on the lever arm while using it to prevent the filament from slipping, especially as it gets further along the PTFE. 

Note that if your filament has multiple kinks in it such as from storing the tip in the side of the spool, or messy winding, that there may be too much resistance for the BSL to push it all the way to the tool. The straighter the filament is, the smoother it will load, but you probably already knew that, eh? :) Also, a 500rpm gearmotor is slower, but has more torque for longer runs and/or bent filament.

BOM: These are NON-affiliate links to the hardware I used:

1. GA12-N20 (12v 1000rpm) gearmotor
2. MK3s+ Dual Drive Gear
3. Hinge Lever Momentary Push Button Micro Limit Switch
4. 9V Battery Clip Connector
5. Optional: 9V Rechargeable Battery

You'll also need 3 M3x10mm socket head cap screws to hold it together, or whatever you have that will work with the provided screw holes. Oh, and probably a piece of wire or two, some solder, and a soldering iron. And a 9v battery. And a screwdriver. ;-)

Check your switch to make sure it's like mine, but the two contacts nearest the hinge point are what I used to make the connection when the lever is pressed down. Use a piece of filament as the hinge pin. Drill or ream out the holes if needed, then melt the ends to keep it from working itself out. The new screw hinge option is designed for M2x8mm socket head cap screws, but something close in size would probably work fine, so long as the lever arm is secure and rotates easily.

My simplistic wiring diagram:

It might take some folding and stuffing to get all the wires in there, as you can see in my photo. Making them as short as possible helps, but also makes it harder to do the soldering. as long as you can get the cover on and mostly screwed shut, it should work fine. :)

Update 2025/03/13 - fixed covered screw holes and other minor adjustments.

Update 2025/03/10 - Added hole for 9v battery charge light, more room for wires, stopper at far end of battery, a little more vertical space/thickness for battery, as well as optional main body top for M2x8mm socket head cap screws for the hinge. Also added lettering bodies for a multicolor print.

Update 2025/03/08 - Added passthrough for USB-C cable for rechargeable 9v batteries.