Yes, you would have to add some type of flag to enter the optical device slot. Make sure to fix it so that the flag passes through the optical interrupter from side to side instead of having the flage enter the slot of the interrupter from the top. If you do the latter the over travel of the motion axis will make the flag bottom out in the slot and possibly bend your flag or break the optical interrupter.

You could try using proximity sensors as well. They might make a cleaner solution depending upon the nature of the movable axes of your machine. It's been a few years since I deployed proximity sensors and so do not recall how good their repeatability actually is.

To be honest virtually all the motion control machines I worked on had the ZERO / HOME sensors that were either optical interrupters or came as an INDEX channel from the linear encoder used to provide the positional feedback for the motion axis.

There were several machines that I worked on where the positional feedback came from a rotary encoder on the axis motor. The rotaty encoder would also have an INDEX pulse that was combined (ANDed) with a mechanical limit switch. The switch was adjusted to that the index pulse from the encoder came when the mechanism was a good amount past the initial closure click of the mechanical limit switch.

Michael Karas