### Update Work Offset for a Siemens Lathe

Rotational alignment by eye to better than 0.4 degree is good enough to run the part program described in the Measuring section initially. Update Work Offset can be used to adjust G56 to make it more accurate.

To update a Work Offset, first add the feature to the part program as shown below.

Menu Navigation for Update Work Offset option

Enter the necessary information into the Update CNC Work Offset dialog screen.

Update CNC Work Offset Dialog Screen

This will update G56 on the Siemens 840D which is initially setup as shown below.

Initial Work Offset Settings for the Siemens 840D Lathe

After running the part program, the Work Offset setting are updated as shown below.

Resulting Work Offset Settings for the Siemens 840D Lathe

Note: The X offset is unchanged as this would compromise the probe tip calibration.

PC-DMIS does this by writing a request file (.req) to the \pcdmis\req folder on the 840D controller where a separate application is waiting to receive it.

On success, the request file is renamed to a .rec file - in this case the file looks as follows:

Siemens 840D Update Work Offset Request File

Ignoring the right-most 0 (zero), the six right-most numbers (with # placeholders where omitted) denote the updates to X, Y, Z, A, B, C axes in reverse order. This is modified in the above case by the axis map of XZbC so it becomes X, Z, blank, C axes in reverse order.