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shared home and limit switches
« on: January 28, 2015, 12:02:37 PM »
I built my own CNC wood router and put limit switches at the end of each axis. I wired the home switches individually and connected to an input pin. I wired other three axis limit switches in series so if one trips it goes to another input pin. I configured Mach 3 with X-- and Home one pin 10 and X++, Y++, and Z++ on pin 13. When machine tries to home it trips the home switch and stops the machine as if the limit is hit. What I want it to do is to activate the home switch and then back off until it's not tripped. Am I missing something in my config?

Thanks
Re: shared home and limit switches
« Reply #1 on: February 09, 2015, 06:18:56 PM »
I actually wired all limit switches in series, (and like you, the negative X, and negative Y limits also serve as the Home switches for each). I never could get it to work with Mach. I ended up disabling the negative limit switch for each in Mach, (although they are still physically wired and positioned to function as limits). As you gain experience with your machine, you will quickly learn WHERE it's limits are physically located. The only real benefit of the limit switches, are the Home switches. So that you can establish WHERE the machine is actually located each time you start it up (and Re-Home the machine). During a Homing Cycle, the axis's are homed ONE AT A TIME. (Z first, then Y, and then X). Mach will move toward the home limit switch, until it strikes it, then back off just enough to un-trigger the switch on Each of the axis. Once homing is complete, subsequent limit switch strikes are interpreted by Mach to be a limit switch as being triggered, which causes Mach to STOP and trigger an error. I know how confusing it all can be, hope this helps you to get your machine up and running!

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Re: shared home and limit switches
« Reply #2 on: February 09, 2015, 11:17:27 PM »
when you home a machine in mach3 it does not see the limit switches it only looks for the home switch.

it should go to the limit switch stop and back off then do the rest that are ticked in port and pin config if its not backing of you may have noise in the wiring you may need to adjust the debounce
Re: shared home and limit switches
« Reply #3 on: December 17, 2016, 05:33:37 PM »
Not sure how Mach 3 or 4 is configured but my experience on industrial cnc routers is that each axis has a home limit switch.  Usually there is an additional switch just past these that is the soft over travel. Usual procedure is to jog the machine away from home position in all axis then set the controller to reference and then this is where Mach is screwed up, you really need to jog all three axis at the same time as it is much quicker.  Anyway jog back until each axis hits its home switch and stops.  The machine is homed,  The machine position DRO should read the same exact numbers as what you have entered in G54 which it will. Load your program and push start. The only time the soft overtravel switches are used is when either the operator or programmer has made a mistake, the keep the machine from going into hard overtravel which is more difficult to get back out of.