This week we had to use some skills we've learnt before to mill a modell in machinable wax and use this to make a silicone mold. The silicone mold then has to be used to cast the object in different materials in our case some resins.
Below the first images from my CAD apllications, I used Rhino to design the Ring because I am more familiar with doing this kind of design within Rhino and the I moved over to Fusion for the CAM part. I had to segment the ring in three parts for milling because we don't have the possibility to mill in 3D - the head part of the ring has some letterings that are oriented around the head in an angle. So I had to unfold or unwrap the part with the lettering flat to have the chance to mill it with the machines we have here in our FabLab. After this is done I have to assemble it manually into the head part and make then the mold of silicone.
Actually the workaraound was not that bad, but it is or was still a problem to mill the lettering in that small scale. So I decided to produce my mold without the letterings - but I will do this later in a 1:1 scale - just to compare the different processes.
Again, because of some problems with the milling I had to manually fix some issues with the wax models - but the final product looked fine. Then I tried a view positions and decided to place the ring on top of a plate with attached cast & ventilation tubes for later casting.
2nd run
Resumee
To achieve a good and clean result with the resin, after mixing the hardener with the resin the mixture has to be degased. That means that with the help of the vacuum chamber the air in the resin is sucked out. This process takes a while because of the viscosity and has to be observed carefully. Especially the timing is important depending on the amount of hardener the pot-life of the resin is varying more or less. By watching the degasing process it reminded me on boiling something or making caramel sirup in a pot. But in a more slow motion action. This bubble action slows down more and more until most of the air is gone, that is the moment when the release valve is opened very slowly to release the door for further processing.
This degasing process is not necessary when the resin is used as "glue resin" for composite structures, if a numbers of materials are processed with high pressure than the degasing doesn't count in - but if a defined amount of resin will be used - let's say as a kind of gel coat for a shine and smooth surface or for castin like in the assignment, than the degasing is recommended if not mandatory.
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