I’ve updated the Paxtruder-0.1 design to address flaws and make enhancements; I present Paxtruder-0.2. After a few more prototype iterations I should have a nice upgrade kit available for those who would like to experiment with various size filaments and multiple extruders.
Improvements from version 0.1 to 0.2
- The captive nut for the thumb screw is held in place by two screws rather than acrylic, which cracked.
- The thermal barrier retainer has been removed. This means fewer parts.
- Fewer unique parts. This method of pressing the filament against the timing pulley requires only three layers. However, a fourth layer is necessary with this motor due to its neck. Since one layer is only a spacer, I made it identical to the retaining layer.
- A 606 bearing is used as in the Plastruder MK4.
- Fewer parts. No thermal barrier retainer, no bearing, no idler wheel, and four layers rather than six (needs only three, but may become as low as two). And all those nuts and bolts we don’t need. You can see how few parts are used in the image below.
- One thickness of acrylic is used for all parts rather than three or so in the MK4.
- Reduced filament replacement time. You no longer have to wait for the MK4 drive mechanism to screw your filament out and back in. Just loosen the thumb screw, pull out the filament, put it back in, and tighten your thumb screw. A ten minute job becomes six seconds!
- Filament pressure can be adjusted while building. No tools necessary!
- It’s smaller. You can fit two extruders in one MakerBot. Wow! Imagine a second extruder on the left of the platform in the image below.
- Other filament sizes work. You can use the same extruder with different sized filaments. I use mine with the standard 3 mm filament and I’ve also been experimenting with a 0.07 inch filament. This will work with any filament smaller than the layer thickness of the acrylic. You will, however, want to use a bore diameter for your thermal barrier and heater barrel which is appropriate for your filament diameter.
- Small enough to be printed without worrying about the edges popping up. Anyone want to convert this to a 3D model?
- One more material. The part that pushes the filament against the timing pulley is Delrin. It’s not expensive, but it’s one more thing to order.
- The motor has to work harder (I think). I haven’t tested the additional friction force resulting from the Delrin because it hasn’t been a problem, but it’s got to be something greater than zero. I think the friction force may be negligible.
- The Delrin will wear out. Some have expressed this concern, but in my tests it has not been a problem. The ABS does not wear away the Delrin and the Delrin does not wear away the ABS. The image below shows the Delrin surface in contact with the ABS after approximately five hours of printing with 3 mm ABS.
- Use a stepper motor.
- Use two layers. A stepper motor with a flat face and no neck will mean the Paxtruder only needs the layer where the Delrin lives and one layer to hold it in place. The stepper motor will act as the other side of the Delrin sandwich. This should make machining a Paxtruder from a solid block easy; it would need only two milled paths and a few drilled holes.
- Bring the thermal barrier closer to the pulley to reduce the space where the filament can bend.