I am looking for ideas on how to prevent my heavy spindle from plunging into the workpiece if the power to the Z-stepper is cut while it is spinning. I do have a brake on the VFD that stops it in 1 second when you turn off the VFD, but not when power is unexpectedly cut. So for 6 or 7 seconds it burns it way into whatever I am working on as it falls down.
My first thought was a spring to balance the force of gravity. But I know that the spindle’s weight is probably the only thing preventing any Z backlash, so in that sense, it is a valuable thing.
My latest seed of an idea is to create a brake on the Z screw that stops the coupler from spinning as soon as the power to the stepper goes away for any reason. How to implement that? I was imagining some sort of ratchet cog fixed to the coupler, and a solenoid with a spring that engages a catch if it loses power. (powering up compresses the solenoid’s spring and releases the brake)
Or do you have a better idea?