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Process:
CAD model is created and validated
Email the CAD file to Brian, the machinist
Foam blank to be machined is glued together (epoxy) to prep for machining
Block is machined in house
Surface prepping begins:
Coat the mold in a thin layer of epoxy resin (plaster and putty can also be used)
Sand the general surface to get it smooth enough for panel lay-up
Fill any holes using surface filler
Repeat sanding and priming process until a smooth surface is achieved
Apply epoxy coat on the final surface to prevent any resin placed later from seeping through the pores of the foam during layup
apply mold release (PVA and wax work well)
https://diyblog.commonfibers.com/blogs/process/plug-finishing https://www.generalplastics.com/wp-content/uploads/2018/08/General-Plastics-Tooling-Molds-Guide.pdf
Pros:
Brian, the machinist, is willing to machine any of the MSXV molds in house so long as they’re made of foam (2 day downtime compared to looking for a sponsor to get a single mold machined)
Lightweight molds, can be easily carried by one or two people (even the larger scale molds)
Sanding surface is much faster than that of MDF (although can be a downfall of the foam if not careful)
Lower cost than that of MDF where a 4' x 8' x 1” sheet comes in at $43.50 (https://www.homedepot.ca/product/owens-corning-foamular-codebord-xps-insulation-48-inch-x-96-inch-x-1-inch-ship-lap-edge/1000155125)
Does not tear off in chunks during machining, and if it did, expanding foam can be used to re-fill that removed section? (assumption)
Cons:
may be leaky (need to treat with chemicals in order to be able to tacky tape to the mold itself)
Rather porous and will need epoxy to prevent any resin during a layup from seeping through
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Requires a foam plug
Creating the plug entails the same process as a full foam mold, so going straight to the foam mold might be time efficient
Ways to make the foam mold include:
https://www.youtube.com/watch?v=MAinuf5I_dw (foam glue together, cut, sand, apply fiber glass, sand, apply putty/plaster, sand, primer, apply mold release PVA and wax work well)
Adding fiber glass onto the foam molds might be a good way to improve the surface finish and make the mold less leaky (plus we have a lot of fiberglass).
Pros:
potentially less sanding (less time maybe)
mold is reusable
better surface finish than just a foam plug
Cons:
more material
more expensive
will still require sanding the foam
more time (maybe)
Aluminum
Process
Pros
Cons
3D printing
https://www.youtube.com/watch?v=4ND2WtEZatY
Thermoforming Molds:
https://www.empirewest.com/thermoforming-mold-design-and-materials.html
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