I have a stepper version of this, dropped it because there is no way to adjust spacing.
@Brian_Albers The force test was without the hot end and each test ended when the filament stripped not when the motor stalled.
@Brian_Albers
I recently did some research on filament forces during normal printing and found that my stepper motor was pushing between 1 and 2kg during normal use.
I think for general purpose 3d printing with good hot end design, a stepper motor and drive gear is all you need.
You’ll see a bit of a write-up on the research with plenty of graphs posted here:
http://airtripper.com/1338/airtripper-extruder-filament-force-sensor-introduction/
Smaller milestone updates are now being posted on my g+ profile.
In my opinion, moving weight should be minimized to get benefit of extrusion speed as ultimaker. Even ultimaker has a top speed of 180mm/s ish.
If an Ultimaker really has a top speed that low, they need to tune their acceleration settings better. I can get a Bukobot with dual carriage-mounted extruders up to 355mm/s, and the limiting factor there is the maximum speed that the microcontroller can send pulses to the stepper driver.