增材制造中滚筒铺粉工艺参数对尼龙粉体铺展性的影响研究

铺粉工艺是基于粉床的增材制造(additive manufacturing, AM)技术中的关键工序之一. 滚筒铺粉工艺参数包括铺粉层厚H, 滚筒直径D, 滚筒的旋转速度ω和平移速度V, 对增材制造工艺中的粉体铺展性具有重要影响. 本文以尼龙粉体为研究对象, 采用离散元法(discrete element method, DEM)模拟其滚筒铺展过程, 建立沉积分数、覆盖率和沉积速率3个铺展性指标. 采用中心复合设计(central composite design, CCD)生成30组仿真案例, 通过响应曲面法(response surface methodology, RSM)拟合了3个铺展性指标的回归模型. 采用方差分析证明了回归模型的准确性和预测的有效性, 并详细分析了工艺参数对粉体铺展性指标的影响规律. 结果表明, 铺粉层厚H是最大的影响因素, 平移速度V是次要的影响因素, 滚筒直径D和滚筒的旋转速度ω对粉体铺展性指标影响较小, HV和DV为影响粉体铺展性指标的主要交互因素. 以3个铺展性指标为优化目标, 采用期望值法对滚筒铺粉工艺参数进行多目标优化, 获得了预测的最优铺粉工艺参数和粉体铺展性指标组合, 并通过实验验证了粉体铺展性指标的预测结果与实验结果吻合良好. 本文的研究结果可指导增材制造中滚筒铺粉工艺参数的优化. 

RESEARCH ON THE EFFECTS OF ROLLER-SPREADING PARAMETERS FOR NYLON POWDER SPREADABILITY IN ADDITIVE MANUFACTURING

The powder spreading process is one of the key processes in the powder-bed-based additive manufacturing (AM) technology. The roller-spreading parameters include the powder spreading layer thickness H, roller’s diameter D, roller’s rotational speed ω and translational velocity V, which have a major impact on the powder spreadability in AM processes. In this paper, the nylon powder was taken as the research object, and the discrete element method (DEM) was deployed to simulate the nylon powder spreading process by a roller. The three powder spreadability indicators including the deposition fraction, percent coverage and deposition rate were established. The central composite design (CCD) model was used to generate 30 groups of simulation cases. The regression models of three powder spreadability indicators were fitted by the response surface method (RSM). The analysis of variance was used to prove the accuracy and predicting effectiveness of regression models. In addition, the effect of process parameters on powder spreadability indicators was analyzed in detail. The results showed that the powder spreading layer thickness H was a leading influencing factor. The roller’s translational velocity V was a less important influencing factor. The roller’s diameter D and rotational speed ω had a slight influence on powder spreadability indicators. Both the H and D with V were determined as the main interactive factors on powder spreadability indicators. The three powder spreadability indicators were taken as the optimization goal, and the multi-objective optimization of roller-spreading parameters was carried out by the expectation method. The predicted optimal combination of powder spreading parameters and powder spreadability indicators were obtained. Moreover, the optimal results were verified through the experiments. The results showed that the predicted results of powder spreadability indicators were in good agreement with experimental results. The research results in this paper can provide guidance for the optimization of roller-spreading parameters in AM.