Research On Digital Micro-jet Control Method Applied To Metal 3D Printing

With the rapid development of 3D printing technology and the increasing demand for industrial applications,metal printing has become a hot topic in the field of rapid prototyping.At present,remarkable achievements have been made in the research of selective laser melting(SLM)at home and abroad.Domestic engine blades,nozzles and heat flow pipes have been made into 3D printing products,which can be used directly,better than castings and sometimes comparable to forgings.In spite of the fact that laser melting technology in printing titanium alloy and aluminum alloy material is more mature,other high-temperature alloys are prone to crack,porosity and spheroidization.But the metal inkjet printing technology can effectively avoid this problem.The world-famous ExOne company has developed industrial grade metal inkjet printer,which can print high precision parts.It has high molding efficiency and wide range of applicable materials.In recent years,a lot of research has been done on the printing of metal ink-jet in China,which mainly involves materials and molding technology.The binder material has been an important factor restricting the development of the technology.In this subject,UV resin is used as a binder to study the metal inkjet 3D printing molding system and molding process.It provides a new idea for metal printing.The specific contents of this article are as follows:(1)The UV resin and digital micro jet technology were studied.The curing principle and advantages and disadvantages of UV resin were analyzed.The driving technology and forming mechanism of digital micro jet were analyzed.According to the analysis results,UV resin and print nozzle used for this subject were determined.(2)The three dimensional printing and molding system of metal inkjet is studied,the process flow of the molding system is determined,the overall structure of the molding system and the mechanical structure of each part are designed.Including the nozzle structure,X-Y planar structure,molding and powder supply structure,powder laying structure.The control part of the system is designed,including the main control board module,the air pressure regulation and the ink supply module,the motion control module,the nozzle driving module and so on.(3)The mechanism of droplet ejection is studied,and the whole process of UV droplet ejection from the nozzle to the completely permeated metal powder bed is analyzed.The maximum penetration diameter and penetration depth of the droplet after completely permeating the powder bed is obtained,and the process parameters are set with reference to the maximum penetration diameter and penetration depth.The results show that the process parameters such as the nozzle temperature,printing speed,layer thickness,pulse frequency and pressure value of nozzle affect the quality of the metal mold.By setting the process parameters reasonably,the nozzle can precisely jet at the specified position,improve the bonding effect of UV resin and metal powder,and reduce the error of forming process.(4)Printing metal test piece,using scanning electron microscope(SEM)to obtain the bond between the UV resin and the metal powder in the model.By measuring the density Km of the model,the better process parameters are determined by combining the molding effect of the model surface,and the gear and other parts are printed under the process parameters.The results show that the metal printing and forming technology is feasible and has important theoretical and experimental significance for metal ink-jet printing technology.