Incremental Casting: The generativ droplet-based manufacturing of parts using aluminum alloys

在过去的20年里，生成式制造方法一直在不断发展。今天，甚至像钛和铝这样的金属也可以使用选择性束熔化技术进行加工。这些技术的缺点是需要特殊粉末作为基础材料，这使得生产的零件相当昂贵。另一种技术是基于液滴的制造，它处理液态金属，因此不需要精心制作的基础材料。该项目的目的是创建一个打印系统，可以以高频率产生铝合金的小液滴。一个小水滴（CA。200 µm）是生产几何精度零件所必需的。需要高频率（100 Hz）才能在可接受的时间内完成。此外，两个后续液滴的复杂的结合过程进行了检查。在该结合过程中，液滴2撞击已经（部分）固化的液滴1。为了使它们之间能够良好结合，液滴1需要部分熔化并与液滴2混合。这意味着，几何形状和粘合质量受到工艺过程中局部热条件的影响。这就是为什么在这个项目中应该详细研究粘合的原因。一个特别的焦点在于合金元素的影响。它们不仅控制表面张力、粘度和热对流等物理性质，而且影响凝固形态。在该项目中建立的安排将能够打印最大尺寸为50x50x50 mm³的零件。

Generative manufacturing methods have been growing constantly in the last 20 years. Today even metals like titan and aluminum can be processed using selective beam melting technologies. The downside of those technologies is the need for specials powders as base materials, which make the produced parts rather expensive. An alternative technology is the droplet-based manufacturing that processes liquid metal and therefore does not need an elaborate base material. The aim of this project is to create a printing system that can produce small droplets of aluminum alloy with a high frequency. A small droplet (ca. 200 µm) is necessary to produce geometrically precise parts. And a high frequency (100 Hz) is needed to do that in an acceptable time. Moreover the complex binding process of two subsequent droplets is examined. In this binding process a liquid droplet 2 hits an already (partly) solidified droplet 1. To enable good bonding between them, droplet 1 needs to partly melt and mix with droplet 2. That means, that geometry and bonding quality is influenced by the local thermal condition during the process. Which is why the bonding should be investigated in detail during this project. A particular focus lies on the influence of alloying elements. They not only control physical properties like surface tension, viscosity and heat convection but also influence the morphology of solidification. The arrangement, which is set up during this project, is going to be able to print parts with a maximum size of 50x50x50 mm³.