双螺杆多材料3D打印挤出机构设计与仿真分析

Design and simulation analysis of the extrusion mechanism of a twin-screw multi-material 3D printer

针对目前3D打印单一材料不能完全满足应用性能要求的现状,设计出一种双螺杆挤出式3D打印多材料的混合打印机构,用于高固含量陶瓷浆料的挤出成型。通过对双螺杆的重要参数进行设计和计算,实现了双螺杆机构的小流率稳定挤出。使用ANSYS的POLYFLOW模块对螺杆转速1~15 r/min下流体的流变特性进行仿真分析,得到整个流道压力场、速度场和剪切速率场的分布规律,仿真结果表明出口流率范围为0.66~6.48 mm^(3)/s,打印速度为2~23 mm/s,适合陶瓷浆料挤出成型。同时对打印机构的混合性能进行评估,得出不同螺杆转速下的材料组分分布,并采用示踪粒子法得到粒子的停留时间分布函数和累积停留时间分布函数;结果表明,螺杆转速越高,其轴向混合能力越弱,自洁能力越强。所设计双螺杆挤出机构可以满足低转速小流率的高精度打印,实现多种材料变组分的实时混合和精准打印。

In view of the fact that current 3D printing single materials cannot fully meet the performance requirements,a twin-screw extrusion 3D printing multi-material hybrid printing mechanism has been designed for the extrusion molding of a high-solid content ceramic slurry.A small flow rate and stable extrusion of the twin-screw mechanism was achieved by designing and calculating the important parameters of the twin-screw.The POLYFLOW module from ANSYS was used to simulate the rheological characteristics of the fluid at a screw speed of 1-15 r/min,and to obtain the distribution of the pressure,velocity and shear rate fields throughout the flow channel.The simulation results yielded an exit flow rate range of 0.66-6.48 mm^(3)/s and a print speed of 2-23 mm/s,which is suitable for ceramic paste extrusion.At the same time,the mixing performance was evaluated,and the distribution of material components at different screw speeds was obtained.The tracer particle method was used to obtain the particle residence time distribution function and the cumulative residence time distribution function.The results show that the higher the screw speed,the weaker the axial mixing capacity and the greater the self-cleaning capacity.The twin-screw extrusion mechanism can meet the requirements for high-precision printing at low speed and small flow rate,and realize real-time mixing and accurate printing of multiple material variable components.