| At present,ceramics SLA-3D printing technology is developing rapidly.The ceramics parts prepared by SLA-3D printing technology have the advantages of high surface quality,high density and high dimensional accuracy,as well as the ability to respond quickly to the rapid preparation of parts with complex shapes.Therefore,it has a good development prospect.However,during the preparation process,parts are often deformed,resulting in poor dimensional and position accuracy.Starting from the dimensional deformation of ceramic SLA-3D printed parts,the key factors that affecting the dimensional accuracy of ceramic parts in the process of SLA-3D printing were studied,the shrinkage deformation model of SLA-3D printed ceramic parts was established,the processing quality of pre-sintered ceramic parts in micro-machining was studied,and the hybrid additive/subtractive manufacturing preparation process for ceramic parts were proposed.The effective process route is as follows:design the CAD model of the parts→ modify the model with the deformation compensation software→SLA-3D printing to form the printed part→debinding and pre-sintering to obtain the green part→improving the dimensional accuracy through subtractive manufacturing→high temperature sintering to form and densified,which provides guidance for improving the dimensional accuracy of ceramics parts prepared by SLA-3D printing.This paper mainly carries out research on three aspects.Firstly,the shrinkage deformation of ceramic parts during SLA-3D printing and was studied,and a non-linear shrinkage model of SLA-3D printed ceramic parts was established,and the non-linear shrinkage deformation prediction and compensation algorithm was proposed.The non-linear shrinkage compensation algorithm was used to process the part model,and the processed model was used for SLA-3D printing additive preparation,and the size deformation control effect was verified;secondly,considering the difficult-to-process property of ceramics,the experimental study on subtractive manufacturing of ceramic green parts(micro-milling)is carried out by adding suitable machining procedures after SLA-3D additive manufacturing and before sintering.The corresponding relationship between the cutting time of micro-milling cutter and the surface integrity of ceramic green part was studied,and an evaluation method for edge integrity of ceramic green parts manufactured by additive manufacturing was proposed.Lastly,A set of hybrid additive/subtractive manufacturing process of ceramic parts and a design method of part deformation compensation were put forward.The dimensional accuracy and deformation of SLA-3D printed ceramic green part were studied.Firstly,by preparing cuboidal ceramic parts with 0.2-5.0 mm edge length on horizontal surface and measuring the size of printed ceramic green part,it is found that the shrinkage deformation of ceramic green part during SLA-3D printing process presents non-linear characteristics.Its shrinkage rate decreases with the increase of size,and the shrinkage deformation was modeled.By measuring the deviation between the dimension of the ceramic green part and the average dimension,the dimension error of the parts in SLA-3D printing process was determined to be ±0.045 mm.Secondly,the influence of the angle between SLA-3D printing plane and laser scanning plane on the surface roughness of the ceramic parts after complete sintering was studied.It is found that the surface roughness was lower when the formed plane was vertical and horizontal,the surface roughness was Ra=0.61 μm and Ra=0.82 μm respectively.The surface quality of parts prepared with layered thickness of 25 μm was obviously better than that of ceramic parts with layered thickness of 50 μm.Finally,the forming effect of SLA-3D printing on small-size features and the mechanism of warpage deformation and the optimization of processing parameters were studied.The results showed that due to the influence of the minimum curing line width,the minimum dimension of SLA-3D printed ceramics green parts on the horizontal plane is 0.2 mm.When the forming dimension is less than 0.2 mm,the machining allowance needs to be designed and removed by subtractive processing.In order to ensure the smooth SLA-3D printing process of and reduce the influence of warpage deformation on the printing process,the mechanism of warpage deformation was analyzed.Through the preparation experiment of flat part,the parameters were optimized according to warpage deformation.The optimized printing parameters were laser power 150 mW,printing layer thickness 50μm,and single layer curing thickness 65.5 μm.The compensation algorithm for non-linear shrinkage deformation of ceramic parts in SLA-3D printing process was studied.Firstly,the characteristics of dimensional shrinkage deformation of SLA printing ceramic part were analyzed,and then the dimensional compensation method of SLA-3D printing laser scanning graph was studied according to the shrinkage deformation model.Laser scanning graph was selected as the compensation object,and the dimensional compensation of the whole part was completed after stacking forming;secondly,using C++to develop shrinkage deformation compensation software for SLA-3D printed ceramics.The software has functions of DXF files reading,graph segmentation,shrinkage prediction and compensation,graph reconstruction,etc.Finally,the non-linear shrinkage compensation algorithm was validated by printing and measuring ceramic precision parts and dimension deformation test parts.The results show that the non-linear shrinkage compensation algorithm has better control effect on dimensional shrinkage deformation,but the tolerance level was still IT11,further precision machining is required to improve the accuracy.After additive manufacture and debinding pre-sintering to obtain green parts,the subtractive processing technology and accuracy improvement of SLA-3D printing ceramic green parts were studied.Firstly.the advantages and disadvantages of micro-grinding and micro-milling in material removal efficiency,economy and machining accuracy were compared comprehensively.Combining with the mechanical properties of the ceramic green part,the ceramic green parts after pre-sintered were selected for micro-machining to improve their dimensional accuracy.Taking tool life and machining surface integrity as evaluation indexes,the optimal cutting parameters of ceramic green parts were obtained as follows:spindle speed 35000 rpm,cutting depth 0.3 mm,cutting width 0.03 mm,feed speed 30 mm/min.Secondly,the machining edge integrity of ceramic green parts was characterized by measuring the average width of micro-chipping and the number of microdamage per millimetre.Finally,according to the size change in the process of hybrid additive/subtractive manufacturing preparation process for ceramic parts,the size of the parts was reverse-designed.By measuring the dimensional accuracy of the ceramic precision parts manufactured by the hybrid additive/subtractive manufacturing preparation process,the precision control effect of the preparation process proposed in this study was verified. |
