Cutting the molds with a CNC
Thanks to the CNC of my school's FabLab i could easily cut my molds directly from wood. I chose to do them from MDF because of the my budget. I hoped it would be strong ans stiff enough
Cutting the shapes
Thank you Paul Gaucher for helping me cut this infinite number of rectangles as well as all the sanding you did !
CNC cutting
After beaing properly attached i started the cutting which was in two phase:
First the CNC rouglhy removes the excess of wood, and then it starts the parallel phase which is more precise
Machining with Autodesk Fusion
Catia has a Machining component however I couldn't get it to work with the CNC. I used Autodesk Fusion to Genereate the GCODE that the CNC reads.
I found Fusion very easy to use and yet powerful.
From simulation to reality
The CNC cut the fuse exactly how i told it to do with the Gcode. The stepover of the parallels was set on 1mm with a flat-end-mill of 6mm
Strengthening the molds
The MDF wood didn't haave a good surface finish and could be polished directly
I added a layer of waterpox epoxy for it to be polished more easily
Surface Finish
To have this surface finish it took me at leat 3 hours of sanding per mold
And I had 14 of them...
Sanding and polishing
To have a nice surface finish I sanded the molds with 240,400, 800, 1200 sanding paper
Before the 800 I applied several layers of the S120 mold sealer and sanded again and again between the layers
I finished by polishing the mold with a polish compound
But the MDF wasn't strong enough..
After having finished EVERY mold I decided to test one
The mold release wasn't enough for the mdf not stick to the carbon..
I had to find another way
Adding a layer of Nylon
The Department of structure of my school gave me a roll of Nylon to put on the molds. The result is just perfect, I didn't even need a mold release! I should have done this from the start to gain more than 50 hours of work...
I will surely use this material in the future however it does need to be on developpable shapes wich is almost the case with the wings but not with the fuselage nor the winglets.
For the fuselage I used an expandable sticky tape of Nylon
The molds before the Nylon layer
You can see almost all the molds but the V-Tail molds are missing on this picture
How it looks with the Nylon
Even though the shape of the mold of the exterior wing with the winglet is not developpable i've put a layer of Nylon which does extend just enough to take the shape of the mold
