Help please - Linear Scale only homing

The trick is to provide a switch in addition to the index on the scale.

If the home switch is already set at the start of homing then the system goes directly to moving at HOME_LATCH_VEL until the switch goes false, and then it looks for the index. You can use this behaviour to let it find the index.

It does need an extra sensor, and a long target that is true for all of one side of the index.

Now I got it,
I thought I have to tinker with the ini,
thanks again

The best solution if you don't have an absolute linear encoder (few do) would be to obtain one with the index mark close to one end.

I know all of mine are near the middle but this makes sense because they were intended for use with a DRO unit on a manual machine. In that application, an index near the middle of the travel allows you to discover it after power up without having to crank the handle all the way to the extreme end of travel.

Actually I'm glad my scales have an index signal. I have already seen linear scales without index signal.

 

Looks like the recommended solution is to add physical homing switches.

The Ursviken press brake I'm working on has one index near top of travel for both left and right ram. Then it has a prox sensor near the bottom of travel, only reachable if the tooling is removed, with limited documentation. It appears these might be for bottom limits to avoid over-extending the hydraulic cylinders.

If I were to try homing to only the index signal... has anyone done this successfully? I searched around a bit and did not find much hope.

I'm thinking of maybe trying to add a home-switch-out-pin to each of the two encoders in the Mesa firmware, on index this pin would always go high during positive counting/ negative during negative counting.

Just bringing this up in case anyone has a better solution. I could always add more sensors/switches. I'd like to complete this retrofit without adding additional sensors to the various axis.

LinuxCNC does support index only homing and seems a
reasonable option on a linear scale with only one index at the end of motion.
 
You would need to guarantee that the axis was not past the index mark
when homing starts...