Study On Precision And Performance Regulation Of Furan Resin Sand Mold For 3D Printing

Sand casting is widely used in industrial production.It can be used to cast engine cylinder block,cylinder head,crankshaft,marine propeller and so on.Among them,sand mold manufacturing is an important link in the casting process.The traditional sand mold manufacturing process involves pattern making,parting,sanding and other processes.The process is lengthy and the error accumulation is large,so it is difficult to produce high-quality and high-performance castings.With the development of additive manufacturing technology,the forming method of sand mold has also made a new breakthrough.In the research and design of sand mold and small and medium-sized batch manufacturing,the speed and complexity of forming sand mold by inkjet printing additive manufacturing technology have been much higher than the traditional manual molding process.As a newly developed advanced manufacturing technology in recent years,the accuracy and performance optimization of inkjet printing sand mold need to be further studied.This paper makes an in-depth study on the accuracy and performance of 3D printing sand mold.The infiltration process of resin in porous media in sand was analyzed by numerical simulation,and the effect of resin infiltration on printing accuracy was studied by response surface experiment;The main factors affecting the shrinkage of sand mold in the curing process are studied,and the full factor experiment is carried out according to the main factors,and the law of printing process affecting the shrinkage of sand mold is revealed;According to the three performance indexes of sand mold strength,gas generation and air permeability,orthogonal experiments were designed,and the influence of process parameters on them was studied.The Pareto front of sand mold performance was optimized by multi-objective optimization method,and the process parameters suitable for aluminum alloy casting were selected and verified.The particle size distribution and average particle size of 70 / 140,100 / 200 and140 / 270 mesh molding sand were measured by Malvin particle sizer,and the permeability of porous media sand mold was calculated by Kozeny Carman equation.In Fluent,the Euler two-phase flow and macro homogeneous porous media model are used to simulate the permeability profile,flow velocity and streamline diagram of resin in each stage of sand.It is concluded that the resin concentration in the porous media in sand shows a gradual decreasing trend over time,and due to the permeability resistance of the porous media in sand bed,the resin flows to the left and right sides,and both sides have a large velocity,The printing accuracy error in the horizontal direction of sand mold is large.The response surface experiment is designed to study the relationship between resin injection amount,curing agent content,sand mesh and printing accuracy.It is concluded that the penetration error of sand mold is between0.22-0.75 mm,which is a positive error.The polynomial prediction model of process parameters and printing accuracy is established,and the reliability of the model is verified.The shrinkage caused by sand mold curing after printing is studied.The influence of resin content,curing agent content and sand mesh on core shrinkage and shrinkage is explored by single factor experiment.It is found that the main factors affecting shrinkage are sand mesh and curing agent content.The full factor experiment was designed for the main influencing factors,the law between shrinkage and process parameters was revealed,and the regression equation was fitted.The shrinkage mechanism of sand mold was analyzed by means of weight loss experiment and laser confocal microscope image.Aiming at the problem that the current 3D printing sand mold takes into account the strength,air permeability and air generation,which is easy to cause complex casting defects,a three factor and four level orthogonal experiment is designed,the influence law of the process parameters of 100 / 200 mesh and 70 / 140 mesh sand mold on the three performance indexes of strength,air permeability and air generation is studied,and the regression model is established.Taking the regression model as the fitness function,the multi-objective optimization is carried out by using the competitive multi-objective particle swarm optimization(cmopso).The Pareto front and its corresponding solution set of sand mold performance are obtained,and the process parameters suitable for light alloy casting are selected and verified.The precision control method of sand mold based on center offset is proposed.The square flange is selected as a typical part,and its casting process is designed.The casting process is simulated and analyzed by Procast software,without defects such as shrinkage cavity,shrinkage porosity and cold crack.The results show that the precision error of sand mold after control is between ± 0.1mm,which verifies the effectiveness of the precision control method of printing sand mold.ZL114 A alloy was used for pouring,and the tensile strength,impact toughness,metallographic structure and the number of pores of the casting were tested.The casting performance printed by the optimized process parameters was better.