Low Profile Filament Runout Sensor

Last crawled date: 4 years, 2 months ago

All the mechanical runout sensor designs I've found seem to have a major drawback: the microswitch is aligned with the filament path. That's fine for bowden setups, where the size doesn't really matter, but on my printer anything on top of the direct drive extruder reduces the available print volume. Of course you can place the sensor away from the extruder, but then you're always left with a length of wasted filament. I've also found a lot of them can be tricky to load/unload and tend to catch the filament.
So I designed my own to try and eliminate these issues. It uses a 5mm ball bearing to actuate a microswitch, which is mounted perpendicular to the filament path. A second ball bearing is used as a contact point rather than a 3d printed surface as I found it gives a much smoother contact; the filament slides through easily and doesn't catch even if it's been chewed up by the extruder or melted out of shape. It also allows for very smooth retraction back through the mechanism when a runout is detected. All that means you can mount the sensor right on top of the extruder, which was my goal with this design.
I've got a balco touch (Wanhao Di3 Plus clone) so I've got a file that'll fit nicely into the extruder assembly. The micro switch is mounted with m2 screws, which can thread directly into the printed part. I've also uploaded the Fusion 360 source files so that it can be adjusted to fit other printers, or to suit whatever size of micro switch or ball bearings you might have lying around.