Prox vs contact for limit, home switches.

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19 Nov 2020 23:21 #189841 by manac
What’s wrong with using roller contact switches for limit and or home switches?
Running steppers with a 7i96. I’ve ordered a pnp nc prox to play with but I have a bunch of rollers.

Second question are limit switches even necessary for a stepper table?
My rack is 1.3M and rails are 1.5M, the way I’ve set it up the pinion will come off the rack before the carriage run into the stop.

Thanks

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19 Nov 2020 23:27 #189843 by tommylight
Nothing really, maybe less precise but far from hindering the plasma performance.
And not really, i do have plenty of machines without them working perfectly well for several years, but they are handy for homing and resuming work if power goes out or a dummy climbs on the table to remove a part that fell of and is sticking out and bumping the gantry. :)
The following user(s) said Thank You: dvn4life1972

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20 Nov 2020 13:20 #189889 by manac
Are prox’s more accurate or repeatable than a micro switch for homing? Your going to cut a piece that’s just laying on the table, it’s nothing like a mill with fixturing.

With ohmic sensing does Z use it or a home switch?
Or another way, if I get the material position using ohmic sensing, isn’t that the home position?

Sorry for all the noob questions

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20 Nov 2020 17:16 - 20 Nov 2020 17:17 #189899 by bevins

Are prox’s more accurate or repeatable than a micro switch for homing? Your going to cut a piece that’s just laying on the table, it’s nothing like a mill with fixturing.

With ohmic sensing does Z use it or a home switch?
Or another way, if I get the material position using ohmic sensing, isn’t that the home position?

Sorry for all the noob questions


I dont know which is more accurate. I would guess prox to be more accurate, but I have roller switches and I had issues when it would click. The release is not at the same place. Another words it would trip at 0 then when going in reverse it would release at .2 which wreaked havoc on gantry squaring for me. Maybe it could have worked if I worked at it but I dropped the roller switches for homing and put them on limit instead.

Home position is at machine 0. Z all the way to the top. Most of the time.
Last edit: 20 Nov 2020 17:17 by bevins.

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20 Nov 2020 20:47 #189923 by chris@cnc
I also use roller switches and have 2 gantry axes. I am very satisfied and accurate to 0.1mm. I trust roller switches more and they have been running very reliably in many machines since the 80s. the only important thing is a flat slope to trigger. I think it's more of a philosophical problem

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