Spindle drop kill switch

Has anyone ever tried to mount a kill switch under the spindle? As in if the spindle drops and starts to create a friction burn in the work piece or spoil board. It would kill all the power.

I had a dumb moment and the spindle was on but the Z motor wasn’t. So it dropped and burned a hole in the work piece. I was there and it didn’t cause a fire but it got me thinking.

It would be nice if I could mount a small switch (like the ones used as end stops) on the bottom of the spindle or maybe even the tool mount. Have it use a relay like the ones a lot of us use for the spindle. If the switch trips then it kills the entire thing.

It would take away a small amount of our workable Z height but not much. A millimeter if I mount it right. And it might not work at all depending on the surface of the work piece. Maybe create a ring that circles the spindle with 3 switches. Or a heat sensor! Oh! This might be an excuse to play with my IOT kit. I’ll bet there is some sort of sensor in it that I could use.

I am just thinking out loud again. Thoughts? Ideas? Jokes? Jokes are preferred.

You may attach relay to “enable” pin of z driver. So whatever firmware disables the stepper it will cut off power curcuit of the spindle

Of course the driver or stepper could be damaged, but that is another case

There are cheap relay boards that have driver transistors and diodes so an enable pin to controo it wouldn’t hurt the driver or stepper.

You can’t leave your machine cutting alone. It is way more dangerous than a 3D printer.

There are so many things that could go wrong with a few microswitches installed near the collet, and if this gave someone the confidence to take a break but wasn’t as reliable as a human, then it’s not improving things.

Any false alarm would ruin my work, with me standing there, at the very end of the job. Anything near the spinning bit has a chance to get into trouble in it’s own, tangled with a big chip, pulled into the bit, etc.

You’d want it to trigger before the collet hit the work, so it would take away from the bit length. That’s almost more valuable than working height.

I had a collet into the workpiece accinldent once. I was literally installing a smoke alarm in the garage while it happened. And I smelled the smoke before I noticed anything else. The alarm did not go off. I shut down the job before it caught the spoil board on fire.