This may seem obvious to some of you, but it's not to me.

I now (basically) understand the construction of a router table, and all 3 axes. I have a clue about bearings, mounts, etc. I understand how the controller software drives the stepper driver card. However, there is one little detail that is nagging at me.

How does the router know where to start cutting? Basically, how does it "zero" itself?

On most printers, if the cartridge is replaced, the printer head does a little dance and resets itself to the top left corner of the paper -- everything is keyed off of this spot.

Similarly, on my old plotters, the paper would dance a little, as would the plotter head, and it would establish a starting point off of which all plotter commands were keyed.

How is this done on a homebrew router? I've heard mention of limit switches, but have no idea what that means...or if that's what does it.

Thanks for any insight you can provide.

-- Chuck Knight