Cheng Tan, Chen Hui, Wei Qingsong
State Key Lab of Materials Forming and Die & Mould Technology, School of Materials Science and Engineering, Huazhong University of Science and Technology, Wuhan 430074, China.
Department of Mechanical Engineering, National University of Singapore, Singapore 117575, Singapore.
Polymers (Basel). 2022 Jun 9;14(12):2345. doi: 10.3390/polym14122345.
In this study, for the first time, a forward-rotating roller is proposed for the spreading of CF/PA12 composite powder in the selective laser sintering (SLS) process. The mesoscopic kinetic mechanism of composite particle spreading is investigated by utilizing the "multi-spherical" element within the discrete element method (DEM). The commercial software EDEM and the open-source DEM particle simulation code LIGGGHTS-PUBLIC are used for the simulations in this work. It is found that the forward-rotating roller produces a strong compaction on the powder pile than does the conventional counter-rotating roller, thus increasing the coordination number and mass flow rate of the particle flow, which significantly improves the powder bed quality. In addition, the forward-rotating pattern generates a braking friction force on the particles in the opposite direction to their spread, which affects the particle dynamics and deposition process. Therefore, appropriately increasing the roller rotation speed to make this force comparable to the roller dragging force could result in faster deposition of the composite particles to form a stable powder bed. This mechanism allows the forward-rotating roller to maintain a good powder bed quality, even at a high spreading speed, thus providing greater potential for the industry to improve the spreading efficiency of the SLS process.
在本研究中，首次提出了一种正向旋转辊用于在选择性激光烧结（SLS）过程中铺展CF/PA12复合粉末。利用离散元法（DEM）中的“多球体”单元研究了复合颗粒铺展的细观动力学机制。本工作使用商业软件EDEM和开源DEM颗粒模拟代码LIGGGHTS-PUBLIC进行模拟。研究发现，与传统的反向旋转辊相比，正向旋转辊对粉末堆产生更强的压实作用，从而增加了颗粒流的配位数和质量流率，显著提高了粉末床质量。此外，正向旋转模式在颗粒铺展的相反方向上对颗粒产生制动摩擦力，这影响了颗粒动力学和沉积过程。因此，适当提高辊子转速，使该力与辊子拖曳力相当，可使复合颗粒更快沉积，形成稳定的粉末床。这种机制使正向旋转辊即使在高铺展速度下也能保持良好的粉末床质量，从而为该行业提高SLS工艺的铺展效率提供了更大的潜力。
