Parallel limit switch connection problem

Sorry for my newbie questions but I still don't understand the idea.
I haven't even set up homing sensors (it still is another matter to learn to me), for now I only want to be able to jog the router off of the limit switch by means of software.
I think you would agree that any machine has its hard limits on both sides. Going in any direction it might drive itself onto the floor if it isn't stopped by a limit switch or some other safety device. But I just can't get the idea of making it possible to override the limits on one side and making it impossible on the other. It really looks weird to me when my router gets stopped by a limit switch and then I have to turn it off, reach it and rotate the stepper motor by hand to make it jog off the switch.
Will the negative homing offset resolve this problem?

Hi

1. Have a reading session.
www.linuxcnc.org/docs/devel/html/config/ini-homing.html .
for master branch or
www.linuxcnc.org/docs/2.7/html/config/ini-homing.html
if you in 2.7 branch.

2. You must home one axis after the other. The order is defined by HOME_SEQUENCE

3. After one axis has found it's zero you have to send it to a position where "his" switch is no more active. By HOME=xxx.

4. Then the next axis is free to run...

Mike

Looking at your picture, I'd suggest your machine is currently in a position that represents X & Y at the maximum positive extents of their travel. You'd be operating the machine facing the spindle at the opposite end of the table from your Y-axis motor, at the left side of your picture. From that orientation, facing the spindle, your gantry is in the upper righthand corner of your work envelope.

If you take this orientation as correct, you need to configure something like this (presuming 1000 mm travel for example):

X Axis:
Your HOME SEARCH VELOCITY is a positive number
Your HOME OFFSET is 995
Your HOME is 5

This gives you 990mm of travel inside of soft limits. Your homing cycle will narrate as:
"Move in the positive direct of Y at HOME SEARCH VELOCITY until you encounter the switch. Back off the switch at HOME LATCH VELOCITY (a negative number in your case, since the sign needs to be opposite from SEARCH velocity), once you've barely creeped backward off the switch, define that exact point as the 995mm positive soft limit of the machine. Now, move backward 990mm to a point which is physically 5mm from the hard end of travel, and name that point axis soft limit ZERO."

So, you've turned the machine on, hit "Home" and this should happen if configured sanely:

1. Your z-axis (ideally homing at the TOP of its travel, with HOME_SEQUENCE = 0!) moves up as far as it can go before the other axes move. This will prevent a lot of snapped tools and gouged tables...
2. Your other two axes are defined with HOMING_SEQUENCE = 1 and 2 respectively, and each in turn finds it's limit switch, latches and moves to HOME.

In my case, my table homes at the operator end. When I hit Home, the spindle lifts, latched and stops, then the X-axis moves to the left, latches and stops, then the Y-axis moves in the negative direction toward me until it finds the switch and latches. As soon a Y-latches, both the X and Y simultaneously move to HOME -- which in my case is the midpoint of each axis.

I guess I'm overcomplicating your situation. I'd suggest you sort out homing before trying to play with axis movement.

If you simply want to fake your machine into overriding a tripped switch you could temporarily wire in momentary contact switch to make or break your loop. I did that during the configuration stage until I had wrapped my head around the concepts involve.

Looking at your picture, I'd suggest your machine is currently in a position that represents X & Y at the maximum positive extents of their travel.

It represents the minimum positive extents. On my first picture, the machine is at 0:0:0 (it's the bottom left corner, like a simple Cartesian system)
I'll try to play around with those variables and see what I get. As soon as I test it I'll put the results here
Thanks for your help

No worries, you can just flip the directions around. the spindle on the "back" side of the gantry threw me off. But my machine is against a wall, making that configuration way too gymnastic for tool changes