Beside the work on the duct mould, we also had to build a rotor.
We need a selfmade rotor, because its shape is not available at the market and important for our usecase. Similar to our duct, the first step was to built a mould. For the first tests, we decided to make the mould rather cheap, so we printed the mould with our 3D printer. Its length of roughly 700mm would not fit in our printer, so we had to split the mould in several parts. After roughly 50 € of material cost and 2 week of printing time, the parts were finished. Unfortunately, the surface was not that smooth to use it directly, so we grinded the mould once, filled the gaps between the parts with some spatula and taped the inner surface with PTFE.
To test our mould we used an easy and fast way of laminating the rotor. Carbon fibre as toplayer and cotton flocks mixed with epoxy resin as core material. To make it resistance against problems and force during the demoulding process we used a rather strong layer structure with mostly unidirectional fibres along its length. After making a template, we cut the carbon fibres. Then we lay them one by one down in our mould and laminated them with epoxy resin. After doing this with both halves, we thicken up the resin with cotton and spread it on the bottom half. The last step was to put both halves together and fixed them with screw clamps.
The next day we demould the rotorblade. It was quiet difficult, because we used to much of the core material, so that it squeezed out everywhere. After that we grinded the edges, which are the results of a splitted mould. We were very happy about the surface and decided to rethink our production process.