## 4 Discussion  
This study discusses the potential of using 3D printing (additive manufacturing) to manufacture products required during the COVID-19 pandemic in the year 2020. Examples of products include face shields, respirators, nasal swabs, and ventilator parts. Face shields and respirators pose an interesting challenge for manufacturers, to ensure that they are fabricated within the shortest time frame in which the efficiency of the design and shortest build time is paramount. However, they need an assembly phase, such as adding a transparent plastic shield or a filter. Parts for ventilators and nasal swabs pose a more technical challenge for manufacturers in light of intellectual patent laws. All the products are still required to have compliance with healthcare standards and regulations. At the moment, some countries suffering from the pandemic have accelerated the approval process for using 3D printing to produce supplies for hospitals. Countries currently facing critical shortage of supplies have even had to bypass some stringent regulations and approval stages with the acceptance of run-of-the-mill solutions. One problematic factor is also the availability of 3D models for certain parts. Companies aim to protect their designs and their intellectual property (IP), but at the same time suffer from their limited manufacturing capacity. 3D printing may allow for an increase in the availability of manufacturing capacity to react quickly, but their unwillingness to share the designs will remain the greatest challenge. Nevertheless, open source community platforms, designers, makers, artists, and even some companies have started to embrace this movement to share their designs and have made  
Figure 2: Total cost of producing a single item as a function of different 3D printers, batch sizes (shown in parentheses), and cost components. collaborative development possible. This chain reaction has sped up the solutions remarkably because people are able to incrementally innovate over each other, and there is a possibility to learn from what others have done. This has been one of the biggest reasons why 3D printing applications related to COVID-19 have been developed so rapidly. Previous work has acknowledged that 3D printing can be used to support the spare parts market [27; 28]. However, it must be noted that patent laws regarding such 3D printed spare parts will need to be further resolved in the future. The COVID-19 pandemic has increased the pressure on manufacturers to make their designs freely available, particularly in cases where spares may not be readily accessible due to disruption in production plants, logistics, and supply chains. Current spare parts are stored as physical inventory for which logistic networks or deliveries may not be functional. Lastly, if tooling is required to re-initiate production, this can contribute to increasing costs for companies and end-users. Another area of contention is that \"repairing patent-protected products with digital spare parts could risk infringing upon the intellectual property rights (IPR) of patent holders\" [27]. For example, to repair a protected device using a spare part, part of the invention may be reproduced, and thereby infringement can occur. Fortunately in most European jurisdictions, infringement only occurs if repair activities are undertaken for commercial purposes, and private use is therefore exempted [29]. The concept of \"repair\" is still interpreted differently in different EU member states, in terms of legitimate repair or when repair counts as infringing upon the rights of the patentee. There has been no agreement on the interpretation of \"repair\" in the EU, and further clarity is needed as to what extent producing, transforming, assembling, or constructing a product is considered to be \"legitimate\".