08-Nov-21
加热时以预定义的方式改变形状的印刷聚合物？由于卓越的可编程材料cpm中的弗劳恩霍夫集群中开发的4D打印技术，现在可以使用。印刷物体形状变化的程度很大：它们可以收缩高达63％。将来，4D制造技术只能在其预定义的形状之后出现特定行为的零件，例如，在医疗技术，机械工程，汽车和航空业组件组件中作为紧固件。
3D打印很流行，作为一种增材制造技术，它具有许多优势。例如，产品和原型可以单独设计并可以快速使用。Fraunhofer CPM的一组研究人员通过使用所谓的4D打印来生产印刷对象，从而大大扩大了好处。该技术将时间（或1D）的尺寸添加到空间的尺寸或3D的尺寸。这样，可以从形状的记忆聚合物中打印物体，这些物体可以在暴露于热量时在以后的时间点上改变形状 - 并且以一种非常出色的方式：杆状样品的长度约为四厘米，最多缩小到四厘米。63％。特定的曲率也是可能的。“我们最初是从相对简单的杆几何形状开始的，但最终我们能够生产出更复杂的空心缸和空心的长方形样品，” Fraunhofer Applied聚合物研究IAP的Thorsten Pretsch博士说，该项目正在协调该项目。在Fraunhofer CPM。“对于我们研究的所有几何形状，我们提前指定了所需的材料行为。”
可以精确调整收缩行为和曲率
There are generally two ways to adjust the response to a temperature increase. The first is the choice of material - here the researchers developed a new thermoplastic polyurethane, or TPU, with shape memory properties. The team also showed that the findings gained of 4D printing can also be transferred to another thermoplastic polymer: they produced shrinkable printed objects from the bio-based polymer polylactic acid, or PLA. The second possibility lies in the clever management of the printing process. “The key is that we give the materials very little time to cool down during printing. As a result, drastic internal stresses are stored in the material. The subsequent shrinkage effect is then very pronounced,” says Pretsch. In short, the choice of material, processing temperature and printing speed can be used to adjust not only the shrinkage behavior, but also the curved state.
Development from monomer to mechanical recycling
The first step in the project was to develop the material and transfer the findings from TPU to PLA. The second step was to develop a demonstrator - a door opener that is shrunk onto a door handle so that it can be operated with the elbow without hand contact. Disassembly is simple: by reheating; the door opener detaches from the handle without leaving any residue. When the print object is no longer needed, it can be ground and reprocessed into filament that can be used at least one more time for 4D printing. »The concept is holistic and future-oriented. In terms of a cradle-to-cradle approach, we have gone through the entire product cycle – from the selection of monomers and polymer synthesis to the 4D printing of a demonstrator and its mechanical recycling,« Pretsch summarizes.
四个Fraunhofer机构贡献了他们的具体专业知识：Fraunhofer IAP合成了形状记忆聚合物，进一步开发了4D打印技术，并进行了机械回收。弗劳恩霍夫（Fraunhofer）机床和成立技术IWU研究所的琳达·韦希特（Linda Weisheit）开发了4D材料可编程刚度的概念。Fraunhofer工业数学研究所ITWM进行了数学模拟来设计演示者。“例如，我们调查了将力在装载时如何在门开启器中分布。我们也有兴趣找出哪种设计在材料消耗方面更好。” HeikoAndrä博士解释说。实际测试在Fraunhofer材料力学IWM机械学院进行。托比亚斯·阿曼（Tobias Amann）博士解释说：“例如，这里的问题是，当门开门时发生了哪些扭矩。”
Source: Fraunhofer Institute
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