Research And Development Of Orthopaedic 3D Printer Based On Fused Deposition Molding Technology

With the development of 3D printing technology and digital medical technology,3D printing for medical treatment has become a hot topic in the new cross-cutting research field.Currently,FDM technology 3D printers on the market can not be directly applied in the medical field,because of its less accuracy,long modeling time,serious salivation/dropping problem,and complex interface operation.This article is intended to research and develop a FDM technology orthopedic 3D printer specialized in manufacturing orthopaedic model.The orthopedic 3D printer would achieve high-speed high-precision performance in modeling human bone model and operation guide,solve the existing technical difficulties,and provide further technical support for orthopedic medical treatment.Firstly,key technical difficulties about FDM technology orthopedic 3D printers is deeply analyzed and studied as while as the features of orthopedic models and the printing trajectory of orthopedic models.The function and performance indicators of FDM technology orthopedic 3D printers are identified,and the overall design on the base of ZYX serial mechanism,with PC plus motion control card as the core of control system,is then developed.Secondly,the detailed design of the mechanical structure and the control system is conducted.The transmission mechanism is designed for effectively alleviating vibration of the 3D printer,feeding mechanism for improving the feeding uniformity,and swing mechanism for reducing the impact of non-working nozzle's dropping problem.The software program of the control system is realized based on PC and C# language environment.A design mode considering doctors' convenience of the interface of orthopedic 3D printer is put forward,and a human machine intercafe with good interactivity is completed.Thirdly,it is proposed to use the contour error as the error evaluation standard,and the method of calculating the contouring error is improved.The dynamic model of the transmission mechanism is established.An analysis of each error factor is conducted based on the simulation model of dynamic error of the transmission mechanism,and the theoretical error of XY transmission mechanism is derived.Fourthly,the influence of each factor on tracking error and contour error is analyzed,then the significant influence factors of dynamic error of XY transmission mechanism are determined.According to the characteristics of the error the XY transmission mechanism,the closedloop PID control and the cross-coupling control are used to compensate the error of XY transmission mechanism.The error compensation control systems are designed,and simulations under actual working condition are conducted.The results show that the two compensation strategis can greatly improve the dynamic performance of XY transmission mechanism,and significantly reduce the tracking error and contour error,and the final error can be reduced to 10?m or less.In addition,an auxiliary control method is proposed to solve the non-working nozzle's dropping problem,which combines the scraping motion control with nozzle cooling on the base of using swing mechanism.Fifthly,series experiments are conducted on the prototype of the orthopedic 3D printer.The results validate the rationality of the dualnozzle swing mechanism as well as the correctness of the error compensation strategy.The orthopedic 3D printer based on FDM technology developed in this article has been applied in Beijing Jishuitan Hospital and other institutions.Research achievements in this paper laid the foundation for industrialization of orthopedic 3D printer and have great value.