Use sensorless homing feature to detect bed crashes to avoid damage?

I am using “BLTouch” for z end stop and like to continue doing so. However, I would like extra protection of torque sensing (at values that are much higher, and perhaps smoothed, than used for sensorless homing) to shutdown or pause motors. Is there a way to do that with TMC UART drivers?

At the least I would like ‘torque threshold exceeded’ detection whenever bed is moving up as z axis motor is very strong and could cause a lot of damage.

With a 4-start z screw it may work. the mechanical leverage from the thread really cuts down the stepper sensitivity, will not work well with 1 or 2 start.

Consider induction probe? it is always in position. i never get crashes. I don’t get why one would bother with BL Touch, if it is retracted, it just adds weight.

I have set up stallguard and wired DIAG pin on my printer for XY and Z (4-start screw) but honestly, it has never crashed.

Advantage of BLtouch is that it works with non-metallic surfaces whereas inductive probe does not.

I did have one crash when trying Mainsail alongside Fluidd and it was not pretty. I would like setup stallguard as a fail-safe, in case I make a mistake, misconfiguration or bug.

With that said, I am looking for a way to enable stallguard to be always on for z axis ( I think by default it is only enabled when homing ) and for klipper to shutdown z motor when stall is detected for more than a second or so.

Yah, it is surface dependant. I’ve no worries with an aluminium 3mm bed. But if you were to have a magnetic surface, hmm. may throw it off. Also, a steel plate on a magnetic surface, on an aluminium plate? Suss.

I’ve only ever used Kapton tape on aluminium tape though, happy with that and I’m in situation where I can wait few mins for bed to cool down and part just lifts off.

im searching for the same for my duett board (tmc 2660) just as a fail safe. Any updates?

The problem here is that stall detection requires calibration. There is nothing stopping you from doing this today… but there is no way to setup a failsafe / trip switch without calibrating by nozzle crashing. A 2nd Zswitch would be a more straight forward solution to the problem you are trying to solve.