Many designs for this style of extruder that I've seen involve tilted rollers. However, I don't have a lathe, so I need a different option. I'm going for vertical M6 bolts instead of tilted grooved rollers, allowing me to fabricate it without a lathe. Additionally, this means that the contact shape against the filament is linear, unlike the hyperbolic shape of the tilted rollers, allowing a more uniform interface.
I'm also powering it with a brushless motor, because the screws mean I need high speed. For 15 mm^3/s, the main body has to rotate about 1600 rpm. Given that I want to use this extruder for high-speed printing, the main body has to be able to rotate at 6000+ rpm, which is way out of the range of okay speeds for stepper motors.