Manual lathe conversions - X axis limit switch mounting ideas sought

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27 Jan 2020 22:04 #155960 by mooser
Not what I was imagining at all but now it makes sense what you described.
I was imagining more of a surface mount "box" held on by a bolt.
I'm going to open the cover and see how much room I have to play with under the cross-slide tonight and go from there. Hopefully the ones I ordered might actually fit but I may have to stick to the mechanical ones (at least for now)
M

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28 Jan 2020 09:12 #155983 by andypugh
Here is a photo showing how I mounted the sensors on my mill.
photos.app.goo.gl/WRJ42XxgwDwzxNRUA

The Y sensor is actuated by a hole drilled on the (non-bearing) edge of the Y slide.
The Z sensor is mounted through the whole guide and actually senses a metal target on the other side. (with slotted holes, for position adjustment)

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27 Feb 2020 00:59 - 27 Feb 2020 00:59 #158590 by mooser
Finally ready to try the inductive X-axis sensor (as usual switching from the micro switch to the inductive one somehow involved moving the x-axis drive motor from the rear of the apron to the front, new pulley, new motor mount, cables and adding a cable drag-chain....)
Anyway, the one I received is a 3 wire, PNP NO shielded switch that I will be flush mounting under the cross-slide somewhat like Andy showed.
On the 7i76 I will leave the z-limit as is (mirco-switch) and just change the X
Field power to the sensor and tie the other to the ground on the 7i76
Signal to the 7i76 input that was on the receiving end of the microswitch before

Do I need to add a small pull-down resistor to the sensor output (1k?) or if the 7i76 ok without it?
Thanks
M
Last edit: 27 Feb 2020 00:59 by mooser.

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27 Feb 2020 09:47 #158611 by andypugh

Do I need to add a small pull-down resistor to the sensor output (1k?) or if the 7i76 ok without it?

It should be OK without.

Are you using steppers or servos?

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27 Feb 2020 12:24 #158622 by mooser
Steppers, never got around to doing s servo upgrade.
I've got another small 2048 encoder with index so later on I might look into installing it on the end of the ballscrew for better homing but really I like the limits for not bottoming out the ballscrew. I'm used to having to reset the tools I guess.

New pendant arrived as well so this weekend I'll try to install this sensor and start looking at wiring the pendant
Thanks again
M

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27 Feb 2020 12:31 #158623 by andypugh
You could consider adding a flag to the motor shaft, pulley, or even use a hole in the belt with an opto to give better home consistency.

I found the prox to be very repeatable under constant conditions. I didn't try warming it up or testing day-to-day repeatability, though.

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28 Feb 2020 01:35 #158711 by mooser
Success... well sort of
Drilled and tapped the apron, installed the switch (can't get a jamb nut on the bottom so I'll have to locktite it in later)
Temporarily ran the wires over to the 7i76 and wired it in (wish the 7i76 had more than one place to grab a field gnd) and the switch works as the home / limit except backwards... as long as the cross-slide is covering it thinks its on the limit and when it reaches the drilled hole that marks the end of the travel it thinks it's clear

Anyway, I'm looking through the HAL for where to invert the switch, I found all the inputs (#4 in my case) and directions but nothing obvious as to reverse the operation of the limit

M

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28 Feb 2020 10:24 #158736 by andypugh

Anyway, I'm looking through the HAL for where to invert the switch, I found all the inputs (#4 in my case) and directions but nothing obvious as to reverse the operation of the limit


Most HAL gpio drivers use a scheme where there are two hal outputs per physical input, .....in and ....in-not.
So you need to change the HAL to link the limit to the ...004...in-not instead of the ...in

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29 Feb 2020 01:57 #158793 by mooser
Perfect
hm2_5i25.0.7i76.0.0.input-04-not

Machined the X-plus slot another .05 so there's some room for error / overshoot before the ballscrew would bottom out. Tapped the end of the cross-slide to put an extension to house the x-minus "hole" and that's enough for tonight
With any luck I can mount the apron / cross-slide permanently this weekend with the new setup
M

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01 Mar 2020 14:58 #158891 by Mike_Eitel
Today i came (again) along a nice video that tried to proof repeatability of these sensors. I think in our cnc machines, especially when they are small and nicely "burried" in metal, we have better results then i saw in my 3d printers.

The following user(s) said Thank You: tommylight

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