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Help with limits not working when homing
« on: March 22, 2007, 08:39:00 PM »
I have a CNC4PC C10 breakout board for all my home and limit switches. Each axis has its own seperate home and limit switch. When I home out my machine, my limit switches don't do anything. I can see them working in Mach 3, but it doesn't have any effect on the machine when they are pressed. Home switches work fine. The only reason I ask this is if my home switch would somehow not work, the machine will overtravel and would keep trying to go until it wrecked something to stop. I'm not sure if this is normal or not. I have an 1/8 difference between where my home and limit switches are in relation to each other so there isn't much room for error.

I have my X,Y,Z,and A home switches wired to pins 6,15,13,12. They are wired as NO switches. My limits are wired in series with each other on same axis. X limits are on pin 7, Y limits are on pin 8, Z limits on pin 3 and A limits are on pin 4. They are wired as NC. Limits all work fine if I jog machine and press one, or if I'm running a program and press one. It will stop the machine instantly, so I know they work. They just don't do a thing when the machine homes. I can see on the diagnostic page that they are working when I attempt to home machine. Home switches also appear to be working fine if I press one on the axis I'm homing, it will reverse motor till I let go and continue to next axis for homing. It dosen't make any sense.   I'm running latest version of mach 3 in demo mode.  I also made sure that the override limits was not on.  I didn't set any soft limits either.

Offline Chip

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Re: Help with limits not working when homing
« Reply #1 on: March 22, 2007, 09:56:44 PM »
Hi, Dave

When Homing, Mach is only looking for Home switch's, limits are turned off till homing is finished.

Why so many switch's, Your limit can double as home SW, NC.

You can actually use only 3 switches wired NC 1 Port Pin, SW's mounted on Moving Axis, striker on each end of travel.

Hope this Helps, Chip
Re: Help with limits not working when homing
« Reply #2 on: March 24, 2007, 09:58:15 AM »
Thanks for the reply.  If I knew this was how it worked, I wouldn't of used the extra switches. All the machines that I have run in the past have always had a limit and a home switch on each axis and the limits still worked during homing.  This seems like it could be a safety issue if the home switch ever failed.

Hood

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Re: Help with limits not working when homing
« Reply #3 on: March 24, 2007, 02:31:35 PM »
you can wire up hard  limits which will cut power to your drives if you wish, in fact I think I remember that the manual recommends it.
Hood

Offline Chip

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Re: Help with limits not working when homing
« Reply #4 on: March 24, 2007, 03:22:41 PM »
Hi, Dave

As Hood stated, An option, I think if you look at the Wiring Diag's on those machines you'll find the limit SW's kill motor power and pause the control.

If your using NC switches, Reset wont reset if any of the switches are open, better than a dirty contact on an NO SW not working.

Thanks, Chip