Study on the basic characteristics of a contactless air film conveyor using viscous traction

Abstract

Many industries require contactless transport of delicate or clean products such as silicon wafers, flat foodstuffs and freshly painted objects. In this study, a contactless air film conveyor for flat objects is introduced. The object is supported by a thin film formed between the object and the conveyor surface and transported by viscous traction which is generated by controlled airflow underneath the object. Experimental and theoretical investigations are conducted on the basic characteristics (flow rate characteristics, film pressure distribution and viscous force). A theoretical model based on Reynolds equation coupling with incompressible Navier–Stokes equation is established to help analyze and understand these characteristics. The results show that air film pressure is symmetrically distributed along the direction perpendicular to the airflow in the actuating cells and non-symmetrically distributed along the airflow direction. The viscous force obtained by differentiating the pressure distribution implies that it consists of an actuating force produced by airflow in the pockets and a drag force resulted from airflow across the dam area. In addition, the influences on the viscous force from gap thickness, suction flow rate, inner bulge and depth of the pocket are discussed.