I can't home the Z axis and set sensible soft limits until I've got a home/limit switch fitted to the tailstock end and a limit switch to the headstock end.
I bought some Honeywell limit switches last week, which finally arrived yesterday. They turn out to be a waste of money if I was planning to use them for homing. There's so much slop they are only usable for overtravel protection. Bollocks.
So instead, I will use these proximity switches. I still have a load of them left over from the Bridgeport conversion. I was a bit concerned about the possibility of false triggering due to swarf but for now this isn't a major concern and I may be able to shield them anyway.
Fitting:
Some cable extension required to get the sensors wired into the 7i76 card.
Little bracket (just a strip of loominum) mounts into M6 holes on the back of the encoder head. The sensors then screw onto those with M3 CSK screws. The target is a piece of angle section, simply held to the encoder body with double sided tape. Sounds Heath Robinson but I'm worried it may actually be challenging to remove later - some heat may be required.
There's no adjustment in this setup but I can recreate this later with some slotted holes perhaps, either for the sensors themselves or the target.
Setup:
This entry in the HAL file connects up the switches:
# external input signals
# --- MAX-HOME-X ---
net max-home-x <= hm2_5i25.0.7i76.0.0.input-00
# --- MIN-X ---
net min-x <= hm2_5i25.0.7i76.0.0.input-01-not
# --- MAX-HOME-Z ---
net max-home-z <= hm2_5i25.0.7i76.0.0.input-03
# --- MIN-Z ---
net min-z <= hm2_5i25.0.7i76.0.0.input-02
Followed by this for the Z axis:
# ---setup home / limit switch signals---
net max-home-z => joint.1.home-sw-in
net min-z => joint.1.neg-lim-sw-in
net max-home-z => joint.1.pos-lim-sw-in
Homes beautifully. The current extent of movement is around 420mm, so the soft limit is set at 410mm. I can rapid into the soft limits at either end without overshooting and overshooting enough to trip the limit switches. Nice.
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