Modular Contact-Free Conveyors for Handling Planar Fragile Objects

Recent studies show that the handling of thin wafers in the photovoltaic industry can lead to unacceptable yields due to cell scratching and breaking. This paper presents the concept and design of a novel modular conveyor that is intended for handling planar fragile objects at a high speed without contact. Each element of the conveyor is a square block that is able to generate tilted air jets that lift and push the object in a single direction. Various handling functions can thus be achieved by the assembly of several blocks. To manage the complexity of assembling systems composed of hundreds of blocks, an automatized design methodology is proposed. This process gives the best topology of the conveyor that meets expected specifications such as trajectory, speed, and travel time. The optimization relies on the physical model of the modular system describing the motion of the object pushed by directed air jets. Experimental comparisons show that the simulation predicts accurately the motion of a glass wafer according to the arrangement of the blocks and the volume of air flow. A maximal speed of 0.3 m/s was experimentally observed and, on larger simulated conveyors, the speed of the wafer could theoretically reach 2.9 m/s.