Sherline mini mill CNC rotary table
The stepper motor is being powered by a simple circuit from a BASIC Stamp BS2p40 microcontroller. You can see the black plastic handle on the red anodized aluminum hand wheel spinning. The motor has 200 1.8º steps (common for stepper motors). The rotary table takes 72 revolutions of the motor shaft to spin 360º, and that's 200x72, or 14,400 discrete locations. That works out to 0.025º, or 1/40 of 1º per step. Not too shabby! These unipolar steppers can be driven in half-steps, yielding 28,800 discrete locations at 1/80 of 1º intervals, but I haven't tried that yet.
Given the 4ms delay per step I set into the motors - any faster and there really isn't enough torque generated per step to fight the load of the rotary table's gearing - the 14,400 steps needed for a full spin works out to 57.6 seconds for a full revolution of the rotary table, which sounds about right. It spun slowly, which is a bit necessary to get smooth cuts on such light duty equipment.
Sherline mini mill CNC rotary table
The stepper motor is being powered by a simple circuit from a BASIC Stamp BS2p40 microcontroller. You can see the black plastic handle on the red anodized aluminum hand wheel spinning. The motor has 200 1.8º steps (common for stepper motors). The rotary table takes 72 revolutions of the motor shaft to spin 360º, and that's 200x72, or 14,400 discrete locations. That works out to 0.025º, or 1/40 of 1º per step. Not too shabby! These unipolar steppers can be driven in half-steps, yielding 28,800 discrete locations at 1/80 of 1º intervals, but I haven't tried that yet.
Given the 4ms delay per step I set into the motors - any faster and there really isn't enough torque generated per step to fight the load of the rotary table's gearing - the 14,400 steps needed for a full spin works out to 57.6 seconds for a full revolution of the rotary table, which sounds about right. It spun slowly, which is a bit necessary to get smooth cuts on such light duty equipment.