To Define Program Zero
To define Program Zero, you have to create or select a coordinate system, which will define the orientation of the stock on the machine and act as the origin (0, 0, 0) for CL data generation. The Program Zero coordinate system can belong to the reference model, stock, or the NC Model assembly; it can be created in Part or Assembly mode, outside of Expert Machinist, or directly at the time of defining Program Zero.
Program Zero for an operation or a machining feature is specified in a similar way, as described in the following procedure.
1. To define the Program Zero, click the box adjacent to 
and select or create a coordinate system. After the Program Zero is defined, the name of the coordinate system appears in the box, and is highlighted in the graphics window.
and select or create a coordinate system. After the Program Zero is defined, the name of the coordinate system appears in the box, and is highlighted in the graphics window.To define Program Zero at the feature level, click the Select arrow next to Define Program Zero in the appropriate machining feature tab. For example, Pocket Feature.
The MACH CSYS or the SEQ CSYS menu, respectively, appears with the following commands:
◦ Select—Select an existing coordinate system, either by selecting on the screen or by using the Sel By Menu command.
◦ Use Prev—Lets you select a coordinate system used for an earlier operation or machining feature.
2. Click Done.
If you click Show, the operation Program Zero is highlighted in red; if you specify a different Program Zero at the feature level, it is highlighted in magenta.