Procedure
SUMMARY OF NOSE CONE MOLD MANUFACTURING
| Step | Estimated Time | Number of People | Notes |
|---|
| CAD Mold in Solidworks | | 1 | Google "Solidworks Mold-making Tutorials" and you can find helpful articles and Youtube videos. |
| Measure MDF layers | 1 hour | 1 | Make sure to leave enough space on either side of the nose cone (and room for pry slits/alignment holes). Account for thickness of blade when marking lines. |
| Cut MDF | 2 hours | 2-3 | Cut the lines as straight as you can, because this will give you nice straight edges that will help a lot with alignment during setup for the router. |
| Epoxy layers together | 2 hours | 2-3 | Epoxy soaks into MDF quickly, so make sure you're using enough epoxy and clamping everything together tightly or you'll get gaps after you start routing. |
| Prepare CAM | | | Make sure your step size isn't too big or the tool will be taking off too much material and create a lot of friction/ruin the tool, etc. |
| Set-up piece on router | | | |
| Route | | | |
| Sand mold | | | |
| Epoxy mold | | | Apply, let soak for 20 minutes, then wipe away. Don't apply multiple times because epoxy doesn't stick very well to epoxy. |
Below is the recommended procedure for making a nose cone mold, learned through trial and error and thanks to the advice of Prof. Mark Drela, an leading expert in aerodynamics and composite layups.
- Obtain necessary supplies
- Medium-density fiberboard (MDF)
- Layup supplies (squeegees, acetone + shop towels for cleaning)
- Clamps
- Sharpie
- End mill for router
- Sandpaper + spray bottle of water
- Mold release wax
- PVA film
- Fine-haired brush
- Bearings or dowels for alignment holes
- Get access to necessary technology
- Router: like a giant mill, drills and moves laterally to route out mold
- Horizontal bandsaw or tablesaw to cut MDF
- CAD mold using CAD of nose cone
- Check out Solidworks mold-making tutorials for help
- If you want a linear section at the base, determine how long (you want at least 2" for enough engagement with the coupler or things will be bendy/not rigid)
- Include holes for alignment pins (around three on each side of the mold). Half-spheres work even better because you can put a bearing inside and alignment will be easier/more accurate.
- Prepare Mold Material (MDF)
- Measure: The amount of MDF you need depends on the thickness of MDF you're using, and the dimensions of the nose cone you want to make a mold for.
- Mark the cut lines in Sharpie, accounting for the thickness of the blade that you're using to cut the material.
- Cut: Using a bandsaw works, but a table saw might be better. Basically you want the lines to be as straight as possible and the pieces you're cutting might be pretty large, so plan on how you're cutting in advance. Having another person is good because you'll have a lot of pieces to carry and it'll be heavy.
- Epoxy layers together
- Route mold
- Prepare CAM
- Set finishing passes (the step size for the roughing cut should be no greater than 1/2 the diameter of the tool you're using)
- Prepare mold (add brackets so you can attach securely to the table)
- Route
- Have vacuum ready
- Zero the router (zero for router and CAM file will be different so make sure you're zeroing correctly)
- Do a test pass offset above the mold
- MAKE SURE THE ROUTING TOOL DOES NOT CUT INTO THE ROUTER BED
- Post-processing
- Sand mold to 500-grit
- Wet sand mold 800-2000 grit
- Add one layer of epoxy
- Mix epoxy (slow-cure)
- Apply thick layer and let sit for 20 minutes. Make sure you get epoxy on the top too, but not in the alignment holes if you have them.
- Wipe excess epoxy away. If you don't wipe it well, sanding will be more difficult later.
- At least 24 hours later, sand to 2000 grit. Shouldn't take too long because the mold should have been very smooth before epoxy was applied in the first place.
- Wax
- PVA film