| New special polymer material polyetheretherketone(PEEK)is regarded as the ideal material for bone repair and bone substitute,which is suitable for long-term implantation in the human body due to its excellent mechanical properties,biocompatibility,abrasion resistance,corrosion resistance and similarity to Young's modulus of human skeleton.However,the current PEEK material itself can only be manufactured by injection molding or laser sintering technology modeling,which limits its clinical practice in orthopedic surgery.As an advanced technology based on additive manufacturing,with the process characteristics of a high degree of customization,short parts cycle,complex parts,Fused Deposition Modeling(FDM)overcomes the PEEK artificial bone production difficulties and makes it customized freely,which will be an important future research direction of clinical medicine.Aiming at the technical characteristics of high melting point and high viscosity of PEEK and the technical bottleneck that FDM equipment cannot finish print it in general,this paper has developed a set of FDM system for PEEK and optimized the modeling process.A new PEEK FDM printing equipment was designed from the whole process design parameters,including the transmission system,the fuselage structure,hot bed and the nozzle system.Then the three-dimensional modeling and assembly of each organization is completed.This paper improves the heating system and temperature control system,and optimizes the internal structure of the nozzle flow channel.Finite element analysis software ANSYS was also used to analyze the structure of the nozzle system,and the structural modal parameters were obtained to provide the basis for the optimization of the nozzle system.The flow of the PEEK melt in the nozzle flow was studied by using CFD FLUENT.The distribution of the temperature,velocity and pressure of the PEEK melt was simulated.The results show that the modeling temperature affects the viscosity of the material,the temperature gradient and the heating rate.The modeling speed is proportional to the size of the runner pressure,and the nozzle velocity distribution gradually decreases toward the center.The temperature field and stress field of modeling process of FDM were simulated based on thermodynamics.According to the characteristics of FDM process,ANSYS parametric programming language(APDL)and "life and death unit" technology were used to control the parameters of different scanning path,scanning speed and modeling temperature.The thermal stress coupling of FDM process was completed.The results of the modeling process under different modeling parameters that improving the modeling environment temperature and printing along the short side can effectively reduce the thermal stress generated during the modeling process are analyzed and compared,which provide the basis for the optimization of PEEK fused deposition modeling process parameters.The standard stretch was made with PEEK by FDM system.In order to analyze the influence of modeling temperature,stratification thickness,scanning speed and material filler on the mechanical properties of PEEK modeled parts,9-group tensile test of four factors and three levels orthogonal experimenta were designed.The tensile strength and elongation at break were compared as the comprehensive technological indexes to obtain the optimal combination of process parameters,which provided the experimental basis for the process optimization. |
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