Fabrication Of Test Pieces Of Wedged Chalcogenide Glass Prism With Precision Compression Molding

Wedged prism contains a fixed angle between two optical flats, and both sides of theend face are perpendicular to the optical flats. Based on features of the structure, wedgedprisms are often used as the target shape for chalcogenide glass tests when using highprecision mold manufacturing technology. By measuring the optical surface quality(including surface shape, roughness and surface damage, etc.), refractive index, andinternal residual stress distribution of the wedged prism after compression molding, we canevaluate and analyze the influences of the precision mold manufacturing process to theoptical performances of fashioned molding chalcogenide glass components.There are some differences in manufacturing concept between the test pieces and thefinal fashioned component products: The fashioned component products need to bemanufactured with large quantities, low cost and high efficiency, and the cost of mold canbe reduced by increasing product quantity, while in the case of test pieces, economic, rapidand convenient manufacturing technology to obtain the process parameters is needed toreduce the costs due to the limited number of test components. The optical performancevariation between fashioned test components and chalcogenide glass preform can be usedas the reference in volume production design and manufacture. Under this technicalrequirements, in the thesis, we present an investigation on precision molding process ofchalcogenide glass wedged prism including mold designs, process parameters, and analysisof the fashioned prisms with fractures, the goal is that the chalcogenide glass wedgedprisms which meet the testing requirements and contain the full process parameters can bemanufactured successfully.In the introduction part of the thesis, the characteristics, application condition and market needs of the chalcogenide glass infrared optical elements are presented as well asthe advantages of producing the chalcogenide glass optical elements by the precision moldmanufacturing process. The necessity of process experiment on the chalcogenide glassbefore mass production is discussed and the major work of this thesis is thus proposed:1). Taking IG6chalcogenide glass as an example, the properties of the material(optical and thermal etc.) of the chalcogenide glass is introduced and the difference of theprocess between the chalcogenide glass and the low Tg glass in the visible spectrum isanalyzed.2). The target shape of the designed wedged prism and the reason for the selection isintroduced.3).Two design schemes for the mold (including the mold material, structure, and theprocessing craft etc.) are proposed based on the material properties of IG6and the wedgedprism shape. The parameters of the compression molding process are designed and themold pressing manufacturing experiments are conducted. The applicability of the twotypes of mold is presented based on the comparison and discussion of the two moldsexperimental results.4). The physical mechanism of the breakage of the wedged prism during the processof the craft manufacturing is investigated through Finite Element Method. It is found thatthe inappropriate setting of the temperature and the pressure is mainly responsible for thebreakage of the wedged prism in the process of the craft manufacturing, which isconsistent with the observation from the manufacturing experiments. The softeningchalcogenide glass will be pressed into the mold gap and the residual stress in the edge ofthe wedged prism cannot be released effectively in the cooling procedure underinappropriate conditions, which leads to the breakage once the value of the stress exceedsthe damage threshold. The final optimized profiling parameter is obtained through the dataoptimizing and experimental verification, which is270℃for temperature and0.3kN forpressing, respectively.The fabrication of test pieces of Chalcogenide glass wedged prism is a necessary technical step to evaluate the influence of the compression molding process on the finalproduct performances. From the point view of engineering, this thesis aims at providingoptimized process parameters, analyzing the technical problems and manufacturingcomplete test pieces of chalcogenide glass wedged prism in the field of precisioncompression molding of chalcogenide glass manufacturing.