Ok, My machine both z-motors are wired in series on one output.

I limit the Z screws on both sides with a clamp on the z screw.

The clamps are 3D printed split disks with screws to tighten them on z-screws

The clamps have a screw sticking down that hits one of the hold down screws on the z-nut as the bed rises.

I install z limit switches on both sides of the bed, these are very touchy until you figure it out.

No code changes, machine goes up until both switches close, one side will “Ratchet” until the other side matches up.

once it is setup, works perfectly .

The z-limit switches should have a very fine adjustment method, Fine thread screw with a lock nut.

You need to go back and forth, one side lower to start, then the other.

It’s Touchy, but not impossible.

Jimbo

I have a circuit that I use to control a semiconductor laser with a Duet2

It uses an OPTO Isolator and prevents the laser from accidentally activating when powered up.

Connects directly to the heater output and works perfectly on my setup.

https://photos.app.goo.gl/i8Mxxm5eNJhgfw...

This is a good guide,

I solved the problem this way.

I mechanically limited the the two lead screws, wired the 2 limit switches in series and made the homez.g go up once to limit, advance 1-2 mm (trip trip trip), rehome. Works perfect every time.

When the table is way off, one side bumps up against the stop until both limit switches close.

I could see this working with 3 and 4 screws too. Just need a limit switch for each one.

All motors need to connect to the Z output. (Series) I think?