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

Attention!

If you have a Prusa XL, you'll want to check out my new loader that mounts to the frame and is always at the ready: 

Also, be sure to check out the remixes for some great optional parts!

About

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 (@12v) gearmotor is slower, but has more torque for longer runs and/or bent filament.

Bill Of Materials

NON-affiliate Amazon links: (if links don't work, use text as your search term)

1. GA12-N20 500rpm @12v gearmotor (check the speed and voltage before buying!)

2. MK3s+ style Dual Drive Gear

3. Hinge Lever Momentary Push Button Micro Limit Switch (black part is 20x10x6.5mm)

4. 9V Battery Clip Connector

5. Optional: 9V Rechargeable Battery

6. Three M3x10mm socket head cap screws

AliExpress links (thx Michael!) (if links don't work, use text as your search term)

1. GA12-N20 500rpm @12v gearmotor (check the speed and voltage before buying!)

2. MK3s+ style Dual Drive Gear

3. Hinge Lever Momentary Push Button Micro Limit Switch (black part is 20x10x6.5mm)

4. 9V Battery Clip Connector

5. Optional: 9V Rechargeable Battery

6. Three M3x10mm socket head cap screws

You'll also need a piece of wire or two, some solder, a soldering iron, 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.

OR, buy a complete, pre-soldered, ready to install hardware kit from Blurolls! 

CLICK HERE TO GO TO BLUROLLS PAGE FOR KIT!

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. :)

For the motor drive shaft adapter, it's pretty hard to design a model that will be a good fit for both the motor shaft and the bondtech gear on every 3d printer with every material. If it's not perfect, then it will be either too tight on the motor drive shaft, or too big for the bondtech gear, or even both! If your first print doesn't fit the motor drive shaft, make adjustments to the scale or extrusion multiplier so that it will fit the motor drive shaft. Then, using the adapter on the motor, spin it against some sandpaper. An emery board (like for nails) works well, to sand down the outer surface until it fits into the bondtech gear. Thanks to Robertguy09 in the comments for that great tip!

Assembly Guide by Teaching Tech

Teaching Tech made an excellent video detailing the entire project! Thanks Michael!

Updates

Update 2025/07/17 - New Main Body top with a separate “direction arrow” frame. Print the arrow separately, and install in the appropriate orientation after you've assembled your BSL and determined which direction it goes. An easy reminder to glance at so you don't have to check the rotation before using it. Also added better support for the front assembly screw as per @mikrom's make. The new top should work with all previous bottoms and remixes of that part.

Update 2025/05/16 - Added new logo inspired by Prusa.

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.