### Update Tool Length for a Siemens Lathe

A similar mechanism in the Update Work Offset is employed to do Update Tool Offset.

Open up the Update CNC Tool Offset dialog box by navigating to Operations | CNC Programming | Update Tool Offset menu option. The Update CNC Tool Offset dialog box is presented.

Update CNC Tool Offset Dialog Box

In this case, the Length and Diameter values are filled in outside of the dialog. Fill in the tool number and click on the OK to create the Update Tool Offset feature in the part program. Use \View\Command mode and navigate to the Length field in the feature and invoke the Expression Builder by clicking on the F2. Select the required length feature such as the measured plane and create an expression that computes the difference between nominal and measured values as shown below.

Expression Builder Dialog Box for Length

Repeat the above procedure for the Diameter as shown below.

Expression Builder Dialog Box for Diameter

This results in the following line added in to the part program:

CNC/UPDATETOOLOFFSET,LOC12.Z.DEV,CIR1.DIAM-CIR1.TDIAM,update.wrk,O1234,1

The Tool Table for Tool 1 which is the OMP400 probe on the 840D is shown below.

Siemens 840D Initial Tool Offset Tool Table

When executed, the following request file is generated. In this case, the right-most figure is the Tool Length update derived from the Plane Deviation and the Penultimate is the Tool Radius update derived from Circle 1 Diameter Deviation.

Siemens 840D Update Tool Offset Request File

The tool table is updated as shown below.

Siemens 840D Updated Tool Offset Tool Table