Gerbs Dual Motor Bowden Extruder

thingiverse

The purpose of these extruder motors is to provide much more power than a single motor design can offer. They prevent stalling due to ground-down filament and ensure the full speed of the extruder motors with no gear reduction. This setup uses two Nema 23 and two Nema 17 motors, allowing for two drive motors spinning in opposite directions. One gear is located on either side of the filament, providing constant tension with a single bolt and spring. The bowden tube runs up to the gears, creating a smooth surface from just a few millimeters away from the gears all the way to the hot end. Cheap filament with uneven tolerances can be easily pushed out with this setup. However, adjustments may need to be made for the drive gear center, which is designed to work with a couple of gears that have an 8mm outer diameter. This setup should work with a large range of drive gears, but specific adjustments may be necessary. You may need to use spacers depending on the shaft length of the motors. The required parts include one screw (4-5mm in diameter, 25-52mm long), one nut for the screw that is no more than 8.75mm wide, a DIY-printed nut would work just fine, and one spring with a maximum diameter of 10 mm and approximately an inch long. Additionally, you will need bolts/nuts to bolt to the Nema 23 and Nema 17 motors, two drive gears that are identical, one Nema 17 motor, one Nema 23 motor (with the same steps per revolution as the Nema 17), a 6mm pneumatic air straight fitting, and some bowden tube with a 4mm outer diameter. The recommended print settings include using a Cobble Bot printer with rafts that don't matter, supports turned off, a resolution of 0.1, an infill of 20, and notes to adjust the shell thickness to 2mm for tapping purposes. After printing, you will need to tap for the pneumatic air straight fitting and ensure it holds securely. Tapping instructions: This design includes a 5.5mm hole for the pneumatic air straight fitting that holds the bowden tube, which will be tapped to a M6 thread. This can be easily changed if needed. Motor assembly: After tightening the set screws, make sure they do not stick out of the drive gears. If your drive gear set screws stick out, it's recommended to grind them down. How I designed this setup: I used a Nema 23 motor, a Nema 17 motor, and my calipers to create this extruder system, getting started with a basic design and working from there.