Replace with Primitives allows you to quickly replace complex geometry with a simple piece of geometry (a Box, Cylinder, or Sphere). You can use the command on multiple bodes or components to substitute a single shape for the original bodies, which are removed. The size of the primitive is initially determined using a bounding shape that surrounds the selected volumes. You can modify the size graphically (using the grips) or numerically (using the size parameters in the dialog).
In the Simplify contextual environment, select Modify > Replace with Primitives .
Optionally, change the Object type to Components to make selection easier.
Select the desired objects to replace with a single simple shape.
Select the Primitive Shape.
Modify the size using the grip arrows on the shape in the graphics window or by entering dimensions in the dialog.
Select OK.