A simple query about homing switches & milling practise

[John S]

Thanks for the quick reply! (Sat night too!)

Yes I know sad bastitch aren't I ?

But how for example, does Mach3 differentiate between the two?

Button on screen just under the DRO's marked Machine Coords, second from right. toggle between the two states, lights up red when in MC.

When I import Gcode, the CNC moves the tool to act upon those coordinates in the G-Code - Mach3 doesn't ask "are these MCs or WCs?") ...therfore if, back to my example, I have a countour line running along X0, the tool will try & get 3mm past that (the diameter of the tool) , but the homing switch will inhibit that.

The homing switch will only inhibit this IF your part is that big it's shape is the same size at the bed travels.
If for example your bed travel in X is say 300mm then the max part you can cut in theory with a 3mm cutter is 300 - 1.5 - 1.5 so 297mm.
In practice it would have to be a tad less because you may get switch bounce.

So how does CNC app differentiate between a home MC of 0,0 & then subsequently interpret / apply WC 0,0 to a different position?

I guess I'm trying to figure how you have two set of coordinates in practise!

The two sets are always there but once set the MC can be switched back to WC and ignored, as stated before goto home or home all will travel to the home switches. Goto zero will go to your WC point.

This WC, MC is one of the stumbling blocks that catch beginners out the most. You can ignore the home switches and not set them if you don't want and just stay in WC and reset 0,0 to the corner of your work and keep changing this from job to job.
You can still have limit switches at both ends for safety, just no home switches allocated.


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