A Low-Binder-Content Ink System for 3D Printing High-Density and Small Feature Size 316L Stainless Steel Parts

Binder ink system is the backbone of binder jet 3D printing (BJ-3DP) technology. Compared with metal injection molding (MIM), BJ-3DP needs much less amount of binder, which means less exhaust gas generation during the debinding process and more environmental friendliness. More than that, low content of binder is also supposed to benefit the structure properties of the printed metal parts. Herein, an ultralow-binder-content ethanol–water–PVP ink system is demonstrated for the BJ-3DP 316 L stainless steel parts by applying thermal bubble inkjet technology. The PVP binder concentration is as low as 80 mg mL⁻¹, which can achieve an ultralow solid content of 0.2 wt% in the printed green part. The two-component solution with water and ethanol provides not only the rheology property adjustment freedom for the ink jetting and infiltration in the metal powders, but also the two boiling points for the step-by-step capillary bridge formation process. By applying the low-binder-content ink, the fully densified 316 L stainless steel parts after sintering can obtain the relative density up to 99.4%, Vickers hardness up to 185 HV, tensile strength up to 542 MPa, 25% elongation at break, and feature size as small as 200 μm.     

Impact of size and location of outflow opening vent on mixed convective heat transfer induced by two aligned heated cylinders immersed in a partially open channel

The current work deals with the numerical investigation of mixed convection occurring from two hot cylinders placed inside vented ducts under different sizes of inflow and locations of outflow opening vents. The mathematical formulation is solved based on the finite volume approach. The location of the outflow section is changed to left, center, and right of enclosure. Impacts of inflow section sizes ($\mathit{O}$₁ = 0.125 and $\mathit{O}$₁ = 0.25), locations of outflow section ($O_2$ = $0.125$), space between cylinders ($0.3\le S\le 0.45$), Reynolds number ($200\le Re\le 400$), and Richardson number ($0.1\le \mathit{Ri}\le 20$) are implemented. Findings display that the average Nusselt number (Nu) is exceeded by 20% for low $\mathit{Ri}$ due to the effect of nonsymmetrical inflow and outflow sections as compared with the case of equal opening vents. For large Ri, a higher Nu is obtained for nonequal opening vents in comparison with the case of equal opening vents by 10%. The difference in the average Nu between left and right cylinders is about 11%. Findings display that the enhancement in Nu due to the large spacing size between cylinders as compared with those of low spacing size is about 35%. The variations of Nu display the opening vents ratio, Re, $S$, and $\mathit{Ri}$ have an extreme action on the characteristics of flow and temperature fields.     

分布式估计算法在考虑差异工件的并行批处理机调度中的应用

论文考虑包含差异工件的并行批处理机调度问题，优化目标是最小化制造跨度.在不违背机器容量的限制下，所有工件需要被分成不同的批次，然后被安排在机器上进行加工.首先根据问题提出一个混合整数规划模型，并提出一个下界；采用FF-LPT规则实现对工件的分批和排序；然后提出基于4种更新机制的分布式估计算法（EDA）来对问题求解.最后通过实验对各类规模不同的算例进行仿真，并将结果和模拟退火算法（SA）、遗传算法（GA）作对比，验证了算法的有效性.     

Influence of Nozzle Parameters on Spray Pattern and Droplet Characteristics for a Two-Fluid Nozzle

In this study, a two-fluid nozzle, as, e.g., used in fluidized-bed or spray drying applications, is comprehensively characterized regarding the spray pattern and droplet size. To analyze the spray cone, the spray cone angle and the radial mass distribution of the nozzle were measured at varied liquid flow rate, spray air pressure, liquid insert bore diameter, and air cap position. Additionally, droplet size distributions were recorded at different spray settings. In general, the overall spray cone and single droplets are significantly influenced by the spray parameters, especially the spray air pressure, as well as the nozzle geometry.