Simple clean out and maintenance procedures for three types of mixers: tilting-drum mixers, horizontal-shaft mixers, and pan mixers. As with any equipment having wear parts, proper clean out and maintenance will increase part life, reduce downtime, and preserve mixing efficiency. Tilting-drum mixers: These rotating-drum mixers discharge by tilting and are used in most central-mix ready mix plants. They have internal blades that mix the concrete by a lifting and tumbling action. Horizontal-shaft mixers: Best suited for mixing dry to very dry concrete, the most common type has a horizontal, cylindrical mixing compartment with two spiral blades mounted on a rotating horizontal shaft. Pan mixers: Also called vertical-shaft mixers, there are several types that all have a cylindrical outer wall and a nearly level floor. The pan may be stationary or rotating, and the mixing is done with paddles or blade-and-paddle assemblies called mixing stars.