Key Issues And The Prototype System Of Rapid DLP Mask Projection 3D Printing

3D printing technology has the advantages of product customization and low cost of manufacturing complex structural models.And is developing very rapidly in recent years.However,the slow printing speed restricts its wide application.In recent years,digital light processing（DLP）based mask projection continuous printing technology has been proposed and greatly risen the printing speed by designing different types of forming surfaces,including gas forming surfaces,polydimethylsiloxane film forming surfaces impregnated with lubricating fluid and liquid forming surfaces based on fluorinated oil.Using such forming surfaces,the printing platform can be lifted continuously.However,these continuous printing techniques are only applicable to hollow structures or thin sheet structures because of the limited resin filling speed during the continuous lifting of the platform,which easily results in printing failure due to insufficient resin filling for the solid structures with a slightly larger area.To address this problem,it is studied in this thesis combines the continuous and layer-wise printing based on continuous printing technology on the liquid forming surface（High-area rapid printing,HARP）.The main work includes as follows:Firstly,we propose a DLP mask projection 3D printing technology by combining layer-wise and continuous printing on a static liquid fluorinated oil interface.The maximum filling distance（MFD）of resin is estimated by experiments.Furthermore,by comparing the maximum-minimum distance(Dis _Max-Min)of the model slices and MFD,the printing pattern（continuous or layer-wise）of the corresponding slice could be determined.For layer-wise printing,the optimal lift height（OLH）for different slice areas is estimated with the objective of fast resin filling.The experimental results show that the scheme can print models with more kinds of structures（solid structures,skeletonized structures,and sliced structures）,and the printing height is not limited by the lubricating fluid.Secondly,a large amount of reaction heat is released in the continuous printing process,which possibly results in the temperature rises of the resin and affects the surface quality of the printed objects.To address this problem,the heat released in the process of resin curing is firstly measured by experiments.And the heat releasing curves are derived;then,a laminar flow control system was implemented,including a resin tank unit,filtration system,cooling system,and power system to ensure a smooth flow of fluorinated oil and a stable printing surface could be formed.Furthermore,the reaction heat is taken away by cooling the flowing fluorinated oil;Finally,the printing control scheme combining the model-guided layer-wise and continuous printing with the laminar flow control system is generated to solve the problem of the temperature rising of the resin.Based on the proposed scheme,the higher model can be printed with high surface quality.Thirdly,we design and implement a DLP mask projection printing control system.The hardware is improved by adding the laminar flow control system.And the model display and processing module is implemented using the C#Wi Form framework on Creation Workshop programming.And the modules of model slicing,layer-wise printing control,continuous printing control,and parameter setting are implemented using C++.Finally,the implemented DLP mask projection rapid 3D printing system is applicable to a wider range of models.