MDF and oak moulds

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MDF and oak moulds

Author	Message
kosak95	k kosak95 posted 4 Years Ago HOT Topic Details
k Group: Forum Members Posts: 14, Visits: 518	Hi all, I have a question regarding making moulds from mdf or oak. I cnc milled 2 moulds, one from MDF and one from oak. Moulds are for bike helmet I want to make. Can you recommend what final layers should I put on mould? What couloring or something like that? I already tried to put some colors but mould got ruined because carbon with epoxy resin glued to it. Please any help and I will be grateful.
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Warren (Staff)	Warren (Staff) posted 4 Years Ago HOT Post Details
Group: Administrators Posts: 2.5K, Visits: 7.9K	Due to its porous nature and movement with temperature and humidity, wood is not ideal as a mould material or surface. At the very least the surface would need to be sealed. A coat of epoxy sanded smooth and polished back to a gloss finish would work to seal the surface. You should then be fine to apply release agents and lay up without issues of the part sticking to the mould. Obviously if you wanted an elevated temperature cure, then you would need to realistically make a proper mould using high temperature compatible materials. Warren Penalver Easy Composites / Carbon Mods - Technical Support Assistant
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kosak95	k kosak95 posted 4 Years Ago HOT Post Details
k Group: Forum Members Posts: 14, Visits: 518	+x Warren (Staff) - 4/21/2020 9:45:44 AM Due to its porous nature and movement with temperature and humidity, wood is not ideal as a mould material or surface. At the very least the surface would need to be sealed. A coat of epoxy sanded smooth and polished back to a gloss finish would work to seal the surface. You should then be fine to apply release agents and lay up without issues of the part sticking to the mould. Obviously if you wanted an elevated temperature cure, then you would need to realistically make a proper mould using high temperature compatible materials. Does that mean I should cover all of the wood with epoxy resin, wait to cure and than sand it and polish to gloss finish or is there some epoxy based paint I should cover the wood with? Thank you for response
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Lester Populaire	L Lester Populaire posted 4 Years Ago HOT Post Details
L Group: Forum Members Posts: 311, Visits: 13K	can be either or. For the MDF i would soak it with a few applications of epoxy resin, then sand, fill and put on a 2K clearcoat. doesn't need to be epoxy, but 1K is asking for trouble in most cases. No experience with oak but would assume it will work in the same way. Then as mould release on paint i like to use a wax based system (I use formula five). I had better luck with that than with a chemical mould release. PVA would be the safest way, but will leave you with a mediocre finish.
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Chris Rogers	C Chris Rogers posted 4 Years Ago HOT Post Details
C Group: Forum Members Posts: 120, Visits: 933	I agree with Lester. You need to seal the wood before you can do anything. You can release off a primer surface or even well resin-coated wood but it still takes some work. MDF will work fine for composites molds provided you don't expect too much. Oak may crack in thick sections and be unstable because of the grain - but I've never tried it! Here's an article I wrote about using MDF for molds: https://explorecomposites.com/articles/tooling/using-mdf-for-composites-tooling/
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kosak95	k kosak95 posted 4 Years Ago HOT Post Details
k Group: Forum Members Posts: 14, Visits: 518	+x Chris Rogers - 4/25/2020 6:31:10 PM I agree with Lester. You need to seal the wood before you can do anything. You can release off a primer surface or even well resin-coated wood but it still takes some work. MDF will work fine for composites molds provided you don't expect too much. Oak may crack in thick sections and be unstable because of the grain - but I've never tried it! Here's an article I wrote about using MDF for molds: https://explorecomposites.com/articles/tooling/using-mdf-for-composites-tooling/ Thanks for reply. I read your article and find it helpful. After you sand first layer of epoxy ? Do you add extra layer of epoxy onto it? Or one is enough? And what kind of paint you put on epoxy then?
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Chris Rogers	C Chris Rogers posted 4 Years Ago HOT Post Details
C Group: Forum Members Posts: 120, Visits: 933	It depends on what you're going to do. I usually only use one coat or epoxy to seal the MDF and move on from there with a primer (and then a 2-part topcoat if I'm really fussing - but usually primer is fine) and use that to build as glossy a surface as is needed. Make sure primers are chemically compatible! You could also use you epoxy as a primer and add another coat and sand that to 600-800 grit (or whatever you feel like) and then apply release. I haven't tested it but my guess is that a mold primer/sealer like Easy Composites S120 (or Chemlease 2737 or Marbocote N1000) followed by a semi-permanent release system would work fine. The surface can't be porous though or it will stick.
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kosak95	k kosak95 posted 4 Years Ago HOT Post Details
k Group: Forum Members Posts: 14, Visits: 518	Hi all, I tried putting epoxy resin on my wood and it didn't look even ( I have round shape of mould so epoxy was always going down), I used cloth rag to spread the resin. I put two layers of epoxy and after first try with only one layer of carbon it didn't stick to mould but after that I tried another one and it stuck. What could be the problem? Can I maybe use only clearcoat? I can spread it nice and evenly on my surface. Will that be a good surface for this? Thanks again
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Lester Populaire	L Lester Populaire posted 4 Years Ago HOT Post Details
L Group: Forum Members Posts: 311, Visits: 13K	you want the epoxy just to seal the wood. apply generously and at the end of the pot live wipe away all excess resin with a shop towel. once it is sealed you can continue with 2k-paint. Usually a wooden surface will not leave you with an acceptable finish with paint and no sealer.
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