Summary 10 Sep 2016
Customized gear teeth, zero backlash gearing of stepper motor and 2-sided milling of V-edges without flipping material makes the Vbird's linear actuator a good design. See repo (currently Rhino+Grasshopper plugin toolchain).
Rack-and-pinion drive mechanism makes Vbird linear actuators scaleable. This and 2-sided milling without flipping material shown in below video:
Two-sided milling also shown at 1:33 in following video:
Zero-backlash gearing of stepper motor shown in following video: