Material Selection

The material used for the main body of the machine is polypropylene (see Table 1 for properties). This material was chosen due to its high strength, stiffness, and working temperature while maintaining a relatively low price and being lightweight [1].

Another material that was considered was ABS. Although this material is more expensive, it has a higher toughness and is more scratch-resistant. However, because this material is mainly used for Lego, there is not a high demand for recycling this plastic[1]. Therefore its recycling options are limited and this would have a big impact on sustainability. Recycling plastic blends is a very expensive process and for this reason, plastic blends such as ABS+PC, although very beneficial,  were excluded from the material selection.

The material chosen for the water tank is polycarbonate (see Table 2 for properties).  PC is a thermoplastic with very high transparency that is very easy to machine. This material is commonly used in kitchenware and housing because of its high resistance to water and common household chemicals [1].  PC is a highly sustainable material as it is easily recyclable. Furthermore, the chosen PC material complies with food-grade regulations and standards within Europe.