Study On Multi-point Injection Molding For Personalized Skull Implants

Focusing on the processing difficulty,serious waste of material and inadequate mechanical property in personalized PEEK skull's production,a novel method,Multi-point Injection Molding,is proposed to solve these problems by combining injection molding and 3D printing techniques.With Multi-point Injection Molding,High performance personalized PEEK skull can be fabricated easily.Injection mold processing is designed and injection mold is made.First,by means of discretization to a continuous plane,a large number of movable square needle are used to complete the construction of molding cavity surface.Second,a personalized PEEK skull blank is formed by injection molding.At last,the personalized PEEK skull implant is fabricated after the blank polished.The results indicate that the average accuracy of the samples is +0475/-0.409 mm,the maximum deviation is +2.725/-2.730 mm,and the Standard deviation is 0.525mmThe influence of injection mold processing has been researched.Single factor analysis is used to detect the influence of the injection temperature,injection rate and injection pressure on the tensile properties of the multi-point injection molding.The results indicate that,the tensile strength of the samples is 72-83 MPa.With the increase of injection temperature,the tensile strength of the tensile samples in 360-375? decreases first and then increases.When the injection rate is low,the tensile strength of the tensile samples increases as the injection speed rise,while when the injection rate is high,the tensile strength will appear fluctuation,which is caused by bubble quality and weld lines problem.With the increase of injection pressure,the tensile strength of the tensile samples in 110-130 bar decreases first and then increases.Cell toxicity experiment of the raw material and the injection sample of multi-point injection molding has been finished.Cell toxicity experiment is conducted to determine whether the injection mold processing generates new toxins.The results indicate that the survival rate of the cells in the raw material leach liquor and the injection sample leach liquor are detected higher than 90%,higher than the negative control group of HMPE.It's proved that the PEEK and the multi-point injection molding are completely non-toxic for the skull repair.