675
« on: February 28, 2014, 12:21:07 PM »
If you are using Mach, imagine standing in front of your mill looking down at the table. The table is like a piece of graph paper, positive X to the right and negative to the left, positive Y away from you and negative towards you. The head goes up and down on the Z axis, positive being up.
If you dial in a positive X movement the table moves to the LEFT, so that the "control point" which is the tip of the tool held in the spindle, moves to the RIGHT relative to the table. Similarly if you dial in a positive Y movement the table moves towards you. If you dial in positive Z the head moves up, away from the table.
For all practical purposes, you can set the "zero" of the XY coordinate system at a convenient point on your work, for example at the "bottom left hand corner". I tend to set the Z zero at the table surface as I have an automatic setting gauge for that; and measure the height of a convenient reference part of the work. Another way is to set the Z zero at the work surface. In either case, as the tool moves into the work Z decreases, and if you have set Z at the work surface, it cuts at "negative Z".
In principle you could label the axes differently, but for example the Mach wizards and at least the CAM program I use (G-Simple) use the above definition so you could get in trouble!