Quote Originally Posted by routercnc View Post
Machine coordinates are where the machine is in absolute space and are set to 0,0,0 by going to (referencing to) the home switches.
Every thing neil says is correct but just want to clear up something that could confuse or be taken wrong by a beginner. Neil says "Absolute" space but this is very different to absolute positioning mode G90 used with-in G-code.
Absolute positioning mode doesn't refer to absolute space but rather it moves an absolute distance in inside the WORK coordinate system. Compared to Incremental Mode G91 which increments by a commanded distance.
ie: G90 X150 would move 150 units away from Work zero. G91 X150 would Increment 150mm from the absolute position so if your at G90 X150 then with G91 X150 you'll end up at X300 absolute work coordinate.

One other slight point I'll make for new folks which I know confuses them is that the Work Zero doesn't have to be on the corner of the Work piece or material. It can be any where you want it to be on the material. Where you located the Zero coordinate in the CAM softare in relation to the part will mostly dictate where on the material you actually place the WORK zero.
ie: For instance if your part was circular like a Wheel for instance then you'll most likely locate Zero at the centre in CAM which means you can't loctate WORK zero on the Corner of material.
In practice often you'll be cutting out of much larger piece of material than the actual parts size so will job to any location that the part will fit within and knowing the Programmed Zero point on the part choose point in that area.


Now to use one switch for Both homes and Limits you need to turn off Home SW safety option in genreal Config. This will tell Mach3 to ignore the Limts while the Machine is Homing.
Your also better to turn on Auto Limit over ride in the setting screen. This will allow you to reset Mach3 and drive off the switch. If you don't turn this on you will need to include a Limit override Switch in your Wiring to knock out the limits while you reverse off the switch.