Something changed with my printer (MG Prusa,

Something changed with my printer (MG Prusa, Marlin firmware) that has be a bit puzzled. When I used to home my Z axis, it would go down, trip the end-stop, then go up just a little and very slowly go down again, leaving the nozzle very close to the bed.

Now, it doesn’t do this every time, sometimes (seems like every-other time, but it’s not entirely consistent) it will go down until it hits the endstop, then back off and stop, leaving the nozzle way too high above the bed.

I’m not sure why this changed, I haven’t changed my firmware in quite awhile, and I’ve tried it with both Octoprint and Printrun so I don’t think it’s a host software thing. I also tried two different versions of Slic3r to see if that made a difference, but no dice.

Any thoughts on why this would change, or how I could force it to work the way it used to?

You could have a microswitch that’s going bad. Most people wire them so they’re default high, and when pressed they go low. On fault, this allows you to trigger them so that you don’t accidentally ram everything trying to hit a faulty endstop. If the endstop is bad, you could be hitting it, backing off, and on backing off it could be triggering quickly again causing the software to think it hit it twice already.

That makes sense @ThantiK , ill try swapping it out and see what happens, thanks!

Y u no use contactless switches?

Like opto’s @Thomas_Sanladerer ? My kit came with mechanicals and I thought they were adequate (but maybe its time to reconsider?)

Short of adjustable hall-effect sensors, (which I don’t know a good source of) optos are a big pain in the ass.

Most microswitches are rated for hundreds of thousands of cycles, they’re repeatable, don’t have to deal with stupid opto flags, don’t get accidentally triggered by light conditions, etc.

I’ve never seen anyone with a nice clean, not-stupid setup for optos on the z axis.

Yeah I was surprised that the switch might be to blame since micro switches have always seemed pretty robust in my experience. Of course it could be something related (wiring to the switch, connection to the ramps board, etc.) as well.

The opto stuff seems cool but also seems more complicated, and I never considered the accidental triggering by ambient light (I get some sunlight in the laboratory in the afternoons).