Grid shift is applied when you need to move the actual zero point that occurs when you hit the marker pulse on the encoder, some times this zero point needs to be moved a from the phyisical position without the need to start messing around by trying to do it mechanically.
A typical example is when a Z axis encoder is replaced and the Z position has to be in an exact spot for the tool changer function. The difference is measured and then plugged into the grid shift parameter by encoder counts for that axis, so that this value will be added or subtracted from the actual zero home position by marker..
Al
CNC, Mechatronics Integration and Custom Machine Design
“Logic will get you from A to B. Imagination will take you everywhere.”
Albert E.