ABSTRACT

Metal FDM process is a valid alternative to costly, energy consuming and less accessible metal Additive Manufacturing technologies. Metal parts were fabricated by means of a low-cost FDM machine with a filament composed of 316 L stainless steel particles and polymeric binder mixture, followed by debinding and sintering treatments. The objective of the study is to investigate the possible influence of some relevant FDM printing parameters on dimensional shrinkage and bulk density of the metal samples. The experimental analysis was conducted by means of a statistical method (ANOVA). Besides, a porosity evaluation was carried out to identify the real density values and the amount of opened and closed porosities of samples characterized with highest and lowest bulk density. Lines infill pattern, extrusion speed set to 20 mm/s and 0.1 mm as layer thickness was the combination of process parameters that ensured the highest nominal density (i.e. 95% of the monolithic 316 L nominal density). The statistical analysis did not show any effects due to the nozzle temperature on the bulk density. X and Y shrinkages settled around 16%, while shrinkages along Z-axis showed a greater variability. The samples with the worst bulk density showed a higher percentage of opened porosity, while the percentage of opened porosity for samples with the best combination of process parameters resulted less than 3%.

摘要

金属 FDM 工艺是昂贵、耗能且不易获得的金属增材制造技术的有效替代方案。金属部件通过低成本 FDM 机器制造，其长丝由 316 L 不锈钢颗粒和聚合物粘合剂混合物组成，然后进行脱脂和烧结处理。该研究的目的是研究一些相关的 FDM 打印参数对金属样品的尺寸收缩和堆积密度的可能影响。实验分析是通过统计方法（ANOVA）进行的。此外，还进行了孔隙率评估，以确定具有最高和最低堆积密度的样品的真实密度值以及开孔和闭孔的数量。线条填充图案，挤出速度设置为 20 毫米/秒和 0。1 毫米作为层厚是确保最高标称密度（即整体 316 L 标称密度的 95%）的工艺参数组合。由于喷嘴温度对堆积密度的影响，统计分析没有显示任何影响。X 和 Y 收缩率稳定在 16% 左右，而沿 Z 轴的收缩率表现出更大的可变性。堆积密度最差的样品表现出较高的开孔率，而具有最佳工艺参数组合的样品的开孔率低于 3%。而沿 Z 轴的收缩表现出更大的变异性。堆积密度最差的样品表现出较高的开孔率，而具有最佳工艺参数组合的样品的开孔率低于 3%。而沿 Z 轴的收缩表现出更大的变异性。堆积密度最差的样品表现出较高的开孔率，而具有最佳工艺参数组合的样品的开孔率低于 3%。