During the course of this project I have been building a hydrofoil. I have had varying levels of success with different techniques to mold the carbon fiber (my material of choice) to the shapes I need: to start off with I tried vacuum bagging around a solid core for the wings and the fuselage, however i found that I struggled to get a uniform surface finish on the finished part because of my inexperience with wet layup of carbon fiber. However, I have been experimenting with using 3d molds and casting the parts I need. I have now cast 4 parts for my hydrofoil out of fiberglass, carbon fiber and epoxy resin. During this process, I have learnt a few things that really helped me to improve the quality of my casts.
With my first molds, I tried to cast directly into the 3D print and this meant that the epoxy resin filled all the gaps in the 3D print and stuck very firmly to the mold so I couldn’t get it out. This resulted in my first fuselage mold being a failure: see below, it had a bit of mold stuck in it. I fixed this issue by lining the mold with clingfilm. I found that this was a good shortcut that allowed me to completely waterproof my molds without having to spend lots of time getting the molds to fit together perfectly and waxing them or using some other release agent. 
Because I had already done some work casting into these molds for my hydrofoil, I decided I would try a different project for this week: I am going to design a set of fins for my windsurf board and then 3d print molds for them. I will also explore how I would CNC these same molds out of aluminium using the CAM aspect of fusion. In order to get the shape for these fins right, I had a look at Maui Fin Company’s (MFC) website: https://mfchawaii.com/eu/shop/windsurf/fins/wave/vf-trifin-thruster/ I decide that I would make the 19cm VF Thruster set. This is a much longer set of fins than my current set on my board. This should give me more drive upwind and earlier planing. I created the CAD model of the fins by using lofts (see week 2 CAD) and then created the top bit where it interfaces with the board with a simple extrusion.
Once I had designed the fins in fusion, I started thing about how to construct a mold for each fin. Because the fins are symmetrical down their center lines, I decided that it would make sense to split a mold down this line and have two halves that fit together. This would allow the finished fin to be released from the mold when its cured. I also was thinking about how the layers of carbon fiber would be aligned in this mold: carbon fiber is very rigid in certain directions depending on the weave pattern and orientation. I wanted the carbon fiber sheets to overlap the edges of the mold a bit so that the fins can be cut down and retain their structural strength. I created a 5mm offset outline to both shapes and then extruded this to get the body of my mold. I then used the combine tool to use the fin model made earlier to cut out its shape from the mold.
I had to split the larger central fin into 2 parts as shown to make it fit on my print bed. I later glued these two parts together. At the time I printed all of the parts vertically standing on their flat end and although this did work, with a raft, I would not do it again in this way. Printing all at once saved time but, At one point during the print, I ran out of filament and although I was able to resume the print the next morning, because of the height the mold split easily at the changeover point which wouldn’t have happened if the print was horizontal. Once both halves were printed, I glued them onto a sheet of 9mm ply and used a staple gun with some small chunks of wood to hold all the pieces in place fully. 
I first put down a layer of cling film on both sides to help remove the fins from the mold when they’re done. Then I cut dry fiberglass and carbon to shape. The construction of these fins is a layer of fiberglass, then one of carbon (oversized on all edges of the mold), then lots of layers of fiberglass inside to give the thickness needed. I then mixed up some epoxy resin: I have found that easy composites is the most cost effective and reliable supplier of both epoxy and composite supplies. I used their fast laminating resin which has a demold time of 8 hours and a fully cured time of 24 hours. I found this was about the right time to give me enough time to work it into the mold (the specified pot life is 12 – 18 minutes) but it was ready to go the next day. I found it made a huge difference mixing the epoxy by weight to get perfect proportions: this gave me a quicker cure time and a stronger part so I borrowed the kitchen scales to do this.
Lots of sanding to do!
CNC Machining.
Although I have no access to a CNC mill at the moment, I was interested to see how I would make this mold on the cnc out of aluminium. This tends to be how carbon fins are made in the real world with a metal mold and prepreg carbon. To test this out, I will use the CAM package in fusion 360.
I set the material to aluminium and opened the Computer Aided Manufacture (CAM) Tab of fusion. After doing this, I started out by watching a couple of YouTube tutorials on how to use the CAM part of fusion.
I needed to setup the CAD to know the size of material it was milling. Once I had done this and set where the origin was meant to be, I was ready to generate some toolpaths. 
I tried to set up a facing operation to make sure the surface of the material is flat and square to the cutter. However, I had the axis set up wrong and because the z axis was in the wrong direction, The facing cut would only cut one of the thin sides of the stock.
I was able to figure out how to flip the axis using the select X and Z Axis drop down in the menu. This meant I could pick the z axis direction by clicking on a face that was in the right direction.
I selected a 12 mm flat end mill to do this facing operation. I then had to specify the depth of the cut into my stock material. This involved setting the bottom, top, feed and clearance heights. I set the bottom height just above the top of my part as this is how deep the facing pass will cut. 
This automatically generated a toolpath as seen. I then needed to cut the actual mold shapes out. I will have to do a 3d contour for the internal shape and a profile for the outside of the mold.I will cut the contour first so that the stock is securely held in place right up until it is cut free with the profile cut. 
I successfully got the program to generate a toolpath for machining the outer shape of the fin mold (a profile cut). This process would be performed last in the real world so all the other features of the part could be machined while it is still firmly attached to the workbed.
Next I tried to do the contour operation to make the shape of the fins in the mold. However, as you can see in the video, the tool path is only running over the top of the mold, it isn’t cutting the 3d shape.
I was at a complete loss as to why this was happening and after watching several tutorials on fusion CAM, I still hadn’t figured it out. I was however able to contact one of my course mates in final year. He was able to show me how to troubleshoot the Tool path generation via an email conversation and a Microsoft teams discussion.
Through this discussion, I found that the software was running into issues because my model was a collection of bodies rather than a component. I opened a new document where I converted the bodies to components and the tool path generated properly!
Once I had managed to get this working properly, I also generated the path for the profile of the fin as well as the pocket at the top of the fin. I changed the tool for these two operations because a square end mill would give a flat bottom to these cuts.
