Study On Al₂O₃ Ceramic 3D Printing Extrusion Head Design And Slurry Forming Process

Al₂O₃ceramics have various excellent properties and stability,and are widely used in various fields of manufacturing.However,various constraints of traditional molding methods hinder the development of ceramic parts.However,3D printing technology can realize moldless free manufacturing,which provides new possibilities for the manufacture of ceramic parts,and the research on 3D printing technology of Al₂O₃ceramics is very necessary.Aiming at the difficulty of processing ceramic parts and other problems,this topic adopts direct write molding（DIW）3D printing technology to prepare Al₂O₃ceramic samples.The influence of Al₂O₃ceramic slurry composition ratio and molding process on its molding quality was systematically studied,the Al₂O₃slurry preparation process for DIW mode was explored,the structural parameters of the slurry extrusion head were optimized and the green body was studied.Printing and drying sintering process,testing the performance of the molded sample,the main research content and results are as follows:（1）Preparation of ceramic slurry precursor and its rheological properties test.Using large particle Al₂O₃ceramic powder as solid phase component,sodium carboxymethyl cellulose aqueous solution as solvent,ammonium polyacrylate as dispersant,and polyethylene glycol as binder,the effects of parameters such as additive content,solid content and p H value were investigated.According to the influence law of slurry viscosity,ceramic slurry with good fluidity,stability and printability was successfully prepared and its characteristic parameters were measured.The results of the main optimal parameters are as follows:the addition of ammonium polyacrylate is 1.5 wt%,the addition of polyethylene glycol is 1-1.5 wt%,the solid content of slurry is 50 vol%,and the system p H=9.The shear thinning behavior of the slurry was explored,and its power law coefficient was determined to be 0.921,the maximum viscosity value was 45.67 Pa s,and the minimum viscosity value was 21.09 Pa s.The extrusion test was carried out on the slurry by manual extrusion.（2）Design simulation of ceramic slurry extrusion head and its extrusion test.Based on CFD technology,combined with the rheological characteristics of the slurry,the fluid simulation and comparative analysis of pneumatic and screw extrusion methods were carried out,and the printing method of pneumatic feeding combined with screw extrusion was optimized.Orthogonal experiments were designed based on fluid microelement force analysis,and the optimal screw structure parameters were determined:screw pitch S=4 mm,screw outer diameter Dd=14 mm,screw inner diameter Ds=8 mm,screw-sleeve clearance I=1 mm,the pressure and velocity changes of the internal flow field during the printing process were obtained through simulation,and the structure at the nozzle was determined to be a double-cone stepped pressure-reducing flow channel structure.（3）Research on the molding process of direct-write 3D printing Al₂O₃ceramics.The influence of extrusion pressure and printing speed on the effect of slurry direct writing was studied through experiments,and its optimal parameters were determined:extrusion pressure was 0.3 MPa,and printing speed v=10 mm/s.Combined with the drying and sintering experiment of the slurry itself,the drying system of the slurry was determined to be natural drying at room temperature for 8 h,followed by vacuum drying for 10 h,the initial temperature was 60°C,increased by 10°C every 30 min,and the final drying temperature was 100°C.Combining DSC and DTG testing to determine the best sintering curve,the macroscopic appearance of the molded sample has no obvious holes or crack defects.（4）Microstructure and performance testing of formed ceramic body.The microstructure analysis and density,shrinkage and other performance tests were carried out on the formed body,and the influence of sintering temperature on the microstructure,shrinkage,relative density and compressive strength of the green body was explored,and the optimal sintering temperature was obtained as 1500℃,the relative density of the molded sample is 96.2%,the compressive strength is 823 m Pa,the microstructure is dense,and there are no obvious defects.