Abstract
Vortex levitation attains non-contact handling by injecting air through a tangential nozzle into a cylindrical cup generating the swirling flow. The precessing of the swirling flow causes pressure fluctuation. This phenomenon becomes apparent as the gap between the cup and workpiece increases, which significantly disturbs the stability of conveyance. In this paper, suppression of pressure fluctuation by a cylindrical column that stabilizes the vortex levitation is described and its mechanism is mentioned. According to the experimental set up, the pressure was measured at the center of the workpiece and the wall of the cup; velocity field under the work piece was visualized by PIV. The result suggested that the larger diameter column denoted the effect on suppression of the fluctuation because the precessing of the swirling flow became stable. On the other hand, variation of the column thickness had insignificant effect on suppressing the fluctuation, but sucking force became weakened since the swirling velocity decreased.
Highlights
In semiconductor manufacturing, a direct contact handling method is used to convey a workpiece: wafers or glass substrates
The magnetic and the electrostatic methods have restricted usage to conductive materials, whereas the pneumatic methods have not; it is applicable to a wide range of materials including: insulator or conductor, magnetic or non-magnetic, rigid or non-rigid and so on because the handling force produced by the air flow is magnetic-free and low-heat-generate [2] [3]
In order to research the reason that pressure fluctuation is suppressed, the time sequence of the swirling flow (a) on the r-θ plane at z = 42 mm under the workpiece was focused
Summary
A direct contact handling method is used to convey a workpiece: wafers or glass substrates. (2016) Suppression of Vortex Precession in a Non-Contact Handling Device by a Circular Column. The vortex levitation, which is one of the latest pneumatic non-contact handling methods, is proposed here. In this levitation, a vortex cup is used to generate the air swirling flow. A number of previous studies have reported the characteristics of the swirling flow in cylindrical chambers and circular pipes [6]-[8], and their technical applications include separation of particles by cyclones and improvement of combustion by swirl burners, among others [9]-[11] These applications cannot be applied directly to the vortex cup because one side of the cup is opened. The interest was paid to investigate the influence of the height and diameter of the column with visualization and pressure measurement
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