Z-axis stop switch not working

My z-axis stop switch is no longer working and my form 1+ is confused because it does not know where to begin.

I started this topic because after a couple of days of reading hundreds of posts (and using the search window to filter them), I did not find anyone talking about this problem.

The z-axis stop switch is at the top of the screw tower (check picture below). The switch is triggered by a piece of metal behind the aluminum arm where the build platform is inserted. The Form 1+ tests this switch every time it is turned on, and every time a print starts. If the switch is not triggered the platform will keep raising until it hits the very top and will start making loud noises, potentially damaging the motor and the lead screw.

I sent a support ticket to formlabs, but I am wondering if anyone has experienced this problem. Moreover, this problem happened during the weekend, so I’ll have to wait until Monday to have a response to my ticket.

By the way, trying to find out how the stop switch works I found a small magnet right at the middle of the screw tower (taped to the right inside wall). Anyone knows the functions of that magnet?

This is a picture uploaded by Hirudin showing the stop switch mechanism.

And this is a video of the problem

The switch is to tell the machine the Z-axis “home” position, or “zero” position.

I haven’t looked closely, but I had assumed that it was an optical switch and that the Build Platform breaks the path of the optical switch to establish the “zero” position.

Sounds to me like a wire has become disconnected possibly. If it is optical, there could be something (dust etc) on the optical switch.

The switch could fail, whether optical / magnetic / physical switch, but a broken or loose connection would cause the same problem.

The one at the top is definitely an optical switch with a metal flag. As for the “magnet” half way down on the right are you sure it is a magnet and not a clip. I assumed at first it was a part of a switch as well but with further analysis I figured it was just a wire clip and the cover it with black tape to make it prettier.

I appreciate your fast response Thomas. I checked for a broken or loose connection at the top and it seems fine to me. Maybe the problem is in the main board. I would check but I could loose the warranty. Any recommendation to check the wires without opening the printer?

Well maybe is a magnetic clip because it attracts other metals. But it seems it is there to hold tight the switch wires.

Rocus / Thomas.

As you both anticipated, the problem was a loose wire inside the printer. Formlabs customer support answered very quickly. They gave me very precise instructions on how to find and fix the loose wire.

Thanks for your help.


Glad you got it worked out.

Excellent! Glad you are back online.