Which type of force is involved in a cream separator?

Centrifugal force

Centrifugal force: In applying the Newton's laws of motion, we have to consider some forces which cannot be assigned to any object in the surrounding. These forces are called pseudo force or inertial force. Centrifugal force is such a pseudo force. It is equal and opposite to the centripetal force.

Example: Cream separator, centrifugal drier work on the principle of centrifugal force.