Over the week, Deborah worked on designing a new frame for the prototype. Bearing in mind the size limits of the 3D printers, she made sure that the prints were within the requirements by breaking the frame up into multiple segments.

First up, we printed the honeycomb structures to allow for airflow into the set-up. By manipulating the processing software for the .stl files, we learnt that we could create a fine honeycomb structure throughout the print piece by toggling with the fill pattern and fill thickness. This saved a lot of our time, rather than manually drawing in the hexagonal pattern on the design software. For most prints, the MnT lab would recommend that we add on a brim to help to anchor the print piece during printing, which is what we did when we printed our first round of honeycomb structures. However, after we printed our first round, we found out that the brim actually is not easy to remove and attempting to remove it will leave an uneven and slightly jagged surface. It is also not advisable for us to sand the surface down as it forms microplastics that are toxic for humans. This was a problem because our parts needed to fit together snugly and any jagged edges would affect the fit. After consulting with Tony, we decided that our prints were big enough such that small movements during the printing should not be as detrimental as it would be to smaller parts. Hence, we printed our subsequent parts without any skirting or brim.

Fig. 1: Honeycomb walls, printed without skirting or brim 

To create a good fit for the radiators, Deborah also designed pieces that would fit around the curves of the components. The pieces were designed with the intention that they would slide together, in a fashion similar to Tetris blocks, to form an overall cuboid frame. In order to do so, we needed to leave roughly 5mm of tolerance on each side to give room for low printer resolution. This was important, especially because we were using the bigger printer which has a lower resolution of 0.8cm. It was with great relief when the parts holding the radiators fit well with the components and the honeycomb structure. With the more complex parts out of the way, we started printing the base of the set-up.

Fig. 2: 3D printed frame surrounding radiators and fans

During this week, our group also realised that it would be more space efficient if we removed the hot water reservoir and turned the set-up into a closed system.  Although removing the hot water reservoir meant that less heat would be sunk into the water, which has a high heat capacity, we were also changing from a two-fan hot side heat dissipation system to a three-fan hot side heat dissipation system. This meant that instead of the heat being removed from the Peltiers and stored in the water, it would be actively removed from the system through radiation cooling.