SnakeBite extruder for 3mm 3D printing filament
by the_digital_dentist, published
Video of operation here:
Update: IT WORKS! It will need some tweaking...
Here it is on a large print: vimeo.com/89872411
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I just tested it with 30 tooth drive gear on the motor and 20 tooth gears on the nuts. This allows the assembly to be reduced in size and theoretically increases maximum print speed. It also increases the load on the motor, and recent test results indicate it increases the load too much. The NEMA-17 motor I am using doesn't seem to have adequate torque to push even one of the 20 tooth gears with the filament in the nut. I'm going to go back to the 30/30 gear device and see if I can get the retraction to work better. More testing this week...
There is a lot of work still to be done. In the video I have the nuts located in-board, so there is a pretty long distance from the entrance to the hot-end. Having the nuts in-board allows for very easy loading of the filament as you can see in the video. I have another version where both nuts are outboard, but had some trouble with those nuts not gripping right, so the one that worked is the one I am testing. Those nuts were made on lathe then tapped by hand. They fit over the ends of the tubes and lined up perfectly.
It remains to be seen how this design handles variations in filament diameter/cross section shape. I am looking into threading a collet from a dremel tool to serve as a nut with adjustable tension.
I think printed gears may not be strong enough for this application, but who knows? Metal gears would allow the size to be shrunk even further, but they tend to be very expensive. The gears I used are actually for 3/16" shaft but its so close to 5mm it works fine and they hang onto the motor and brass tubes tightly.
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Use NEMA-17 motor, 6-32 screws to hold cover on base, 8-32 screws to mount on printer carriage, M3 screws to motor.
One nut is left hand threaded, made by tapping mild steel with left hand tap, the other is standard 6-32 nut. Both are soldered to 5mm ODx 0.45mm wall brass tubing. 625Z bearings (5x16x5mm) are pushed onto tubing. Gears come from American Science and Surplus or ebay, also pushed onto tubing.
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