A tray engine includes a vertical drive column, a rotation mechanism for rotating the vertical drive column, and an end effector attached to the vertical drive column. The end effector includes an end effector base attached to the vertical drive column. The end effector further includes a slide attached to the end effector base to support a tray, when present. The slide enables the tray to slide along a length of the end effector base. The tray engine includes a drive mechanism attached to the end effector base for moving along the length of the end effector base to enable the tray, when present, to slide linearly along the length and load or unload the tray to or from the slide.