External Trim allows you to make an external profile cut or series of cuts around the outside of the boundary. The External Trim consists of the trim operation and the cutoff operation.
Trim is the main tool path that cuts the material to be removed. This leaves a tab that keeps the material from falling.
Cutoff cuts through the tab to let the material to be removed fall.
The figure below illustrates the function of these operations.
The Cutoff operation is optional and is generated only if it is specified as If you created an External Trim Sequence, you will get an additional Cutoff operation. If you created an External Trim operation, the cutoff pass will be included in the External Trim operation.External Trim Operations
The External Trim operation is available for both 2 and 4 axis machines.