a 1/4hp 220v 3 phase motor (36rpm) controlled by a hitachi VFD (VFD=variable frequency drive)
The VFD is programmable with 100's of parameters some including:
accel/decel start/stop (adjustable times individually)
constant speed depending on torque (measuring powerconsumtion) and adjusting accordingly.
warnings of overload (adjustable range) and if so dropping speed or stop.
speed 0-200hz (50hz is standard in sweden)
etc etc..
It also have a lot of inputs and outputs for switches, potentiometers, computer control,
network connector etc..
I am now also rebuilding my setup for eventually using more than one heater and longer meltzone
( i have to short i think because the pellets does not have enough time to mix fully with masterbatch unless i run really slow), and i want to run much faster extrusion.
I get 2.85mm +-0.03mm variance as of now (vertical) without programming any torque variations on the VFD.
The best part is i got them dirtcheap 