Abstract
Recently, the development of displays requires large, thin glass substrates, and air film conveyors equipped with porous pads have been developed to transport the substrates in a noncontact state. In this study, a contactless air film system with aligned porous pads is proposed. Experiments and analysis of its basic characteristics are conducted. First, it is confirmed that the flow rate characteristics of the porous pads can be represented by a modified Forchheimer equation with the determined permeability and inertial coefficient. Then, a theoretical model based on the Reynolds equation is established to analyze the film pressure distribution. The results indicate a parabola-like shape distributed along the radial direction in the porous area and an approximately linear curve in the periphery area. Furthermore, the experimental results indicate that the bearing force and static stiffness increase if the clearance decreased with a given flow rate. Finally, a numerical calculation performed by solving the coupling equation of elasticity and the modified Reynolds equation shows an approximate quadratic shape in the deformation, and the experimental results supported this to a certain extent.
Highlights
In semiconductor manufacturing, fragile equipments, such as silicon wafers and glass substrates for liquidcrystal display (LCD), are conventionally conveyed; that is, they come into contact with the transportation device
The results of the flow rate characteristics demonstrate that a modified Forchheimer equation can be used to characterize porous media including effects from both viscosity and inertia
The permeability and inertial coefficient can be determined experimentally, allowing the supply flow rate to be rapidly predicted in practice based on the supply pressure
Summary
Fragile equipments, such as silicon wafers and glass substrates for liquidcrystal display (LCD), are conventionally conveyed; that is, they come into contact with the transportation device. Keywords Noncontact conveying, glass substrate, porous pad, pressure distribution, air film
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