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Author Topic: Switches for Home position  (Read 1808 times)

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Re: Switches for Home position
« Reply #10 on: February 01, 2018, 06:53:58 PM »
Hi Gordon,
thats a good idea.

You may have seen the photo I posted earlier in the thread. With these roller switches you don't have to put them
at the end of travel. You may also have noted that the aluminum ramp which activates the roller is on a slotted
mount which allows you to adjust it somewhat. The repeatability that they offer would provide a good way to confirm
your axis calibration.

The real question is why do you need to check the calibration? I set (steps per unit) mine four years ago and have not
touched it since. There are other maintainence/development items which would improve my machine rather than checking
calibration which has not changed in the life of the machine.

Craig
My wife left with my best friend...
     and I miss him!
Re: Switches for Home position
« Reply #11 on: February 02, 2018, 10:57:15 AM »
I use roller switches similar to Craig's - maybe even identical - for both homing and over-travel end stops.  Have not had any issues with them yet.

I wrote a homing routine to bump into the roller switches, then back off until I saw the "Z" signal on the optical encoder on the servo motor shaft.  Nice routine, I made the code real pretty, it was real accurate, but over the years I went back to just using the roller switch as it was close 'nuff, AND I could hear the switch "click" and I knew I was good to go.

Only time it is a problem is when i get junk on the roller.  But that is a problem with any switch.

____

Possibly a little OT, I set my limit switch close to the end of travel, and make the LS's target keep the switch plunger pushed in all the way until the over-travel is hit.  That way I know when i start to "home" which direction i need to move the axis.
Re: Switches for Home position
« Reply #12 on: February 02, 2018, 04:12:20 PM »
Hi MadDog,
luv the name...
Quote
Possibly a little OT, I set my limit switch close to the end of travel, and make the LS's target keep the switch plunger pushed in all the way until the over-travel is hit.  That way I know when i start to "home" which direction i need to move the axis.

That's a good idea. I have my home switches about 3mm inboard from the end of travel. Under almost any conceivable circumstances I only ever need to start homing
in one direction. Has worked for three years without me crashing it and I can crash just about anything!

Your right about the repeatability of the switches, I was going to go for index homing as well, and now that I'm using Mach4 its built in and trivially simple but I
realize I don't really need it. I get 0.02mm or better...that's enough. There are other ways I can spend time and money without trying to track down 0.01mm that I don't
need.

Craig
My wife left with my best friend...
     and I miss him!