Experimental Buffer 3D Printing

Experimental FDM 3D printer filament buffer, active feeder, automatic filament reloader

See video introduction at

BOM list
0. A set of printed parts
1. 370 motor, 6000 RPM or higher, voltage can be selected, 12V or 24V are both acceptable, choose according to power supply conditions
2. Worm gear D6, L10 or longer, 0.5 module
3. One BMG extruder gear
4. Two MR85ZZ bearings
5. One D5L25 dowel pin
6. Approximately 10 M2*10 self-tapping screws
7. One 0.6*5*15 spring; if the elasticity is insufficient, a 0.7mm wire diameter can be used, choose spring steel material
8. Two PC4-6 pneumatic fittings
9. Two PTFE tubes, length depends on your needs
10. One D5 steel ball or glass bead, placed on the filament detection micro switch
11. Two small travel micro switches
12. DC female socket, M8*0.75 thread, or direct wiring can be used, other aperture sockets require drilling modifications
13. One 604ZZ bearing (inner 4 outer 12 thick 4)
14. One M4*10 grub screw

The above accessories are for reference only, please make your own adjustments if there are discrepancies

The total cost is approximately 20 RMB, it will be lower if you reuse spare parts

Working Principle
There are two micro switches, one is responsible for filament detection, which conducts when filament is present, and the other is responsible for buffer detection, which conducts by default and disconnects when the feeding buffer is full. After the printer uses a small section of filament, the feeding switch conducts, feeds for a short period, then disconnects and stops feeding after the buffer is full. This cycle repeats, and the micro switches will click repeatedly during operation
Application Scenarios
1. Acts as an active feeder for the printer, eliminating the need to manually insert filament every time
2. Reduces the tensile load on the printer's extruder, improving extrusion performance and print quality to a certain extent
3. Automatic filament reloading. If paired with a T-junction, a single buffer can complete one automatic reload. With two buffers, continuous automatic reloading from left and right can be achieved. For the specific working principle, refer to the rubber band automatic reloading solution
4. Maximizes residual filament utilization. Using the automatic reloading function allows you to fully use up the remaining filament on each spool. If the tail end has a barb, reloading might fail. A jam and self-cutting device can perfectly resolve this issue
Known Drawbacks
1. Only one filament detection switch is used, there's a small chance that the filament, just after passing the micro switch, gets stuck on the BMG extruder gear and breaks, causing the subsequent small piece of broken filament to jam and prevent the printer from pulling it through and using it up
2. The motor lacks a power-off mechanism for abnormal operation. If the extruder skips filament, the motor will continuously free-spin, leading to prolonged power-on heating, potential overheating, or even fire hazard!!!
3. The micro switch has a limited lifespan, theoretically around 10,000 cycles, but replacements are inexpensive
4. Other unknown drawbacks and risks are to be assessed and borne by yourself