Procedure
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)
- Sandpaper + spray bottle of water
- Mold release wax
- PVA film
- 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.
- Measure, cut and glue MDF layers
- 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
- Prepare CAM
- 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
- descrbie
- PVA film