## 7 Conclusions and Future Prospects  
This paper has reported on our experience as a research group (PIA (Process optimization, Information Management and Applications) at KIT, Karlsruhe, Germany) participating in a German campaign against the COVID-19 crisis by using our 3D FFF printing facilities along with our expertise and being part of a larger manufacturing/supplier hub for the production of medical and sanitary equipment with zero lead time. The fused filament fabrication technology proved to be the most convenient technology in this situation, as it is relatively easy to quickly set up a manufacturing environment. Due to the low costs of printers and material, the widespread use of FFF also enables a lot of makers to join forces and produce a large number of parts almost without any lead time. Open software applications and platforms also allow for sharing individual models, making it possible for hobbyists with no access to sophisticated CAD or modelling software to print complex designs and support movements such as the makervavirus coalition. One can conclude that infrastructure sharing has proven itself in the context of a sharing economy as a promising measure for rapid and targeted access to urgently needed infrastructures and in its capacity to cope with crisis situations. Supplying 3D printed PPE for hospitals, medical staff at doctors' practices, and even in refugee camps with no hands-on or in-depth background in actual mass-production runs has given us the opportunity to experience the chances and challenges of zero lead-time additive mass manufacturing firsthand. It allows us to give feedback on the requirements that have to be taken into account when adopting AM for manufacturing processes. The experiences described above show that a connected manufacturing environment that includes **constant feedback loops and communication between designers, material suppliers, production engineers, and logistics** is crucial for AM-based manufacturing approaches. While this might be easy to implement for industries already operating in a just-in-time fashion, such as the automotive industry, it might be more difficult for small enterprises that are facing other challenges such as the implementation of internet-of-things (IoT)-approaches or higher degrees of automation at the same time. The need for stocking spare parts and having an in-depth knowledge of each printers' individual drawbacks and failure-prone parts can be challenging if only limited staff can be assigned to the adoption of AM. This experience has, however, reinforced one of the main benefits of AM technology: its ability to **react and adapt to change as quickly as possible, a prerequisite for the enabling of an agile manufacturing environment**. This became immediately evident to us as the time taken for the complete deployment of all printers for this effort was only a matter of days from when the decision was made to support the project until full production capabilities were reached with two shifts deployed. This effort proved beneficial as it was an efficient solution that met the requirements for PPEs from the start of the crisis and until others were able to mass-produce the face shields or ear savers using conventional methods. Therefore, **3D printing was validated as an efficient agile production technology**, supported by the fact that it is relatively inexpensive to adapt towards changes that may occur in design or parameters, while also enabling the ability for continuous improvement. In contrast, other production processes such as injection molding require significant investment for the research, development, and production of tools, after which the design is pretty much locked. However, as 3D printing becomes a more industrially-relevant manufacturing technique, the support of printer manufacturers, reliability of the printers themselves, and the consistency and quality of materials has to evolve as well, providing a much more robust production alternative to classic subtractive or molding techniques.