HANOV Dual Drive Gear Printable Extruder

The design priorities of this extruder are:

• Cost. Made from inexpensive, easily available parts.
• Can be printed and assembled easily
• Compatible with many bowden printers, including Ender 3, Monoprice Select Mini and others.
• Easy filament loading. A funnel shaped path lets you get the filament in every time without bumping against the sides.

Materials needed

You only need the gear kit, bowden fitting, and some M3 screws and 1 M6 nut.

• 3X M3x6 screws to attach the motor
• 1X Prusa / Bondtech gear kit or clone, including 3mm rod, two needle bearings, two gears and one M3x2 grub screw.
• 2X M3x30 screws
• 1X M3 nut for tensioner
• 1X spring for tensioner
• 1X washer for tensioner
• 1X M6 nut for bowden fitting
• M6 pneumatic connector for PTFE tube

If you already have M3 screws, a washer and a spring, the total cost is $8 USD for the other parts. Add $25 if you want quality hardened gears. 

Printing

First, determine if you need the adapter plate.

• Mounting directly to the motor: Yes
• Mounting to a surface about 2mm thick: No
• Mounting to a surface less than 2mm thick: Yes. Scale adapter plate in Y direction.

Print all parts as oriented, using supports from the built plate only. Make sure no other supports are used, because you don't want to be poking them out of the little holes afterwards.

• 5 walls
• At least 20% infill
• Supports from build plate only

Now, take the M6 nut and press it into the hole on top of the extruder. The pointy part of the hexagon should point straight up. It should not take much force.

Use the pull-through technique to place an M3 nut into its place.

Step 1: Adapter plate

If mounting directly to the motor, you will need to print the adapter plate. It provides a flat surface on which to mount.

If mounting to a surface, you may or may not need the adapter plate. Its purpose is to lift the extruder past large circular platform on the motor. You can scale it in height to be the exact thickness you need.

This printer does not need the adapter plate:

Step 2: Attach one gear to motor shaft

Your motor should have a D-shaped shaft. If it has a round shaft instead, you need to file the grub screw down so it doesn't stick out. The M3 grub screw is 2mm, and you will need to get this down to 1.6 or 1.7mm. If you have a D-shaft motor, you can skip this step.

Find the one gear with the grub screw in it. As designed, if mounting directly to the motor, the bottom of the gear should be 5mm from the circular platform on top of the motor. Put it there for now but leave the grub screw loose so you can adjust it later.

Step 3: Attach extruder to motor adjust the final gear height

Use three shorter screws to attach the back plate to the motor. Now, slide a piece of filament through it and do final adjustments to the height of the drive gear. Once it's right, now is the time to use thread-lock on the grub screw.

Step 4: Prepare the lever

Put the two needle bearings inside the remaining gear, and put it inside the lever. Make sure the orientation is correct. Then slide the rod all the way down through the gear until it is flush with the top surface of the lever.

Step 6: Attach lever to the extruder

Slide the lever onto the back plate. It may need some pressure to get it all the way down its hinge. 

Place the rod retainer plate on top of the lever and use the M3x30 screw to fasten the whole thing to the motor.

Step 7: Tensioner

Use the washer, spring, and long screw to create a tensioner and loosely tension the extruder.

Now you're all ready to go and calibrate E-steps!