Research On A Novel Three Dimensional Printing Jet Device Based On High Speed On-off Valve

Rapid manufacture by graded adding material is the way of three dimensional printing,which breaks the limitation in manufacturing complex parts by traditional methods and shorten the manufacture period substantially,and it also becomes an important part of next generational manufacturing.Besides in rapid fabricating mold,it also has the broad applications in electronic industry,medical model,pharmaceutical engineering and tissue engineering.One of the key points of three dimensional printing is the droplet control,which includes thermal bubble jet,piezoelectric jet and solenoid valve jet.For the method of solenoid valve jet,switching spool rapidly is applied to form discrete droplet,and the injecting flow-rate can be greatly promoted for the larger valve core size,so it has the advantage of high flow.However,slide valve structure is generally used by current solenoid valve jet,and the low frequency inhibits the quality promotion of the jet.Therefore,in this paper,a new jet device with high frequency is proposed based on rotary high speed on-off valve,and its characteristics are analyzed comprehensively.Firstly,a novel jet device based on rotary high speed on-off valve is designed for the three dimensional printing jet system.The corresponding mathematical model is developed based on the principle and feature of the device.The changing of open area formed by triangle and rhombus is analyzed,which can be used to analyze the static and dynamic characteristics.Meanwhile,the hydrodynamic force acted on jet device and the friction resistance between spool and sleeve are analyzed,and the key sizes are given taking the design rules into consideration.Then,the flow characteristics on static and dynamic condition are studied combined with Computational Fluid Dynamics.The three-dimensional fluid mode of the jet device is calculated,the pressure and velocity distribution rules are obtained,and it is also verified by the developed mathematical model.The flow characteristics with different frequencies are contrasted,the flow characteristics affected by duty cycle and frequency are analyzed.Moreover,the relation of duty cycle and flow is studied and the relevance between the frequency of spool and three dimensional printing precision is discussed.In addition,the deformation of jet device in temperature rising state is researched taking the viscosity-temperature characteristic of classic material into consideration.Combined with the material property and its viscosity-temperature characteristic,the fluid operating temperature is obtained,which can meet the demand of jet in high-efficiency.The temperature distribution of jet device is researched based on the fluid-solid coupling method,and its structure thermal deformation is also analyzed.On this basis,whether the deformation of spool and sleeve with high temperature in the allowable range is analyzed.Finally,the dynamic characteristics of developed three dimensional printing jet system based on new jet device are researched.The basic model of three dimensional jet system controlled by rotary valve is built.The influence of damping coefficient and rotational inertia is studied through analyzing the motion equation of spool.The simulation model of jet system is set up in Simulink,the influence of rotary frequency,jet device parameters,nozzle parameters and material property on jet performance is discussed,and the dynamic features of designed system are also researched.The innovative point of this paper is the proposition of a new three dimensional printing jet method controlled by rotary valve,and the designed device considers the characteristics based on three dimensional printing and high speed on-off valve to promote the jet flow-rate and stability.With the mathematical model and numerical calculation,the key features including structure parameters,inner flow field,rising temperature,deformation and system realization of the new device are investigated.