The Virtual Machine Shop

secondary zero return

CNC programming uses the G30 code word to rapid to the secondary machine zero position by first passing through the programmed point. For example G30 X2 Z10 will return to the secondary machine zero position (wherever that is) after first moving to X2 and Z10. This is a useful command for avoiding fixture obstructions. G30 serves the same purpose as G28 except that is uses a secondary machine zero. A secondary machine zero point is usually for pallet changing machines and is available on only a few of them (usually horizontal machining centers).