About Creating Automatic Volumes
You can use the Automatic Volume command to create volumes without sketching the required geometry. The command requires you to use a cubical or a cylindrical shape to create a volume. Retain the coordinate system that is selected by default as the reference about which to rotate or offset the automatically-created volumes. Alternatively, you can create a coordinate system or select or modify an existing coordinate system. Select one or more quilts or surfaces of a part model as references.
After an automatic volume is created, you can achieve the volume precision by offsetting or moving the automatic volume. You can also split the automatic volumes to create mold inserts.