i machined some molds from wood with the intension of only producing a few parts. i plan to poor soft urethane into the mold halves to produce sort of like a caul plate and try compresing the wet layup between the cured urethane plug and mold surface with the hopes i will have minimal air entrapment and a decent finish.then i plan to remove the 2 cured halves, trim, put back in the mold and bond the 2 together
my first question is how should i treat the wood surface. no matter what ill use PVA for the first attempt and second is do you think i will have sucess with the above described process? the part is fairly small, about 12" X 4". thanks
well, wood will always be porous… this is me and i might be stupid but: first thing that came to my mind is using a thick automotive primer and then sanding it down (i see you got some lines left from the cnc machine) and then spray it with an automotive color… OR, spray gelcoat inside, and again sand it down…
Several coats of wood sealer, wax, then PVA. Thats the only thing I can think of.
Yeah, wood sealer and primer. Then you can sand it to a nice mirror (depending on primer) finish, and then start with mold releasing. Semi perm, or pva/wax. I’ve done wood sealer and semi-perm with only slight success.
Of course, it WAS a split 4x4 square mandrel. gonna suck no matter what material!
how long did that take to program and machine? Did you make the design?
What is it? My guess is a rc helicopter canopy
Wood sealer for sure. Then primer or just wax and pva. Smooth the wood sealer (if not primering) up to 1500 grit sandpaper.
Nice mold:cool: Man I wish had more funds and full time access to a CNC mill.
that part looks like it could have been done on a CNC router?
thanks for the replys guys. i took your advice on the sealer. i called minwax today and told what appeared to be a knowledgeable person exactly what i was doing and they told me to use their stain, sealer which i did followed by a their top coat of clear urethane which i will do. i was contemplating using the primer as mentioned. but i figure this way i have product compatability. ill test the adhesion of the urethane before i do the lay up.ill sand ,polish,wax, and pva. pva should provide the safety margin anyway.
snocutt, yep its another heli canopy. it took about fifteen minutes to program althouhg i spent several hours creating the design and solid model
fasttr. this was made on a cnc mill turning a 1/2 ball end mill at 7500. not really a wood working machine but it got the job done. thanks for the complement. now if i can just manage to pull a nice part out of it.
Bit late for tis but when doing my shipwrights apprenticeship we used to coat timber/hadboard etc with shellac the mold realese wax & often just wipe in some pva with a peice of foam(cushion), if it came out a bit rough we’d just tune up the first part & make a gelcoated mold of it. All the best from jeff
the parts came out pretty good. i just wanted to say thanks to all who contributed to this thread, and this great message board in general. i will have to say the most exciting thing you guys have turned me on to is the spray adhesive.it has made working with the dry fabric sooooo much easier. i wish i would have none about this when i was messin’ with composites years ago. i have posted pics in the “showcase” forum. thanks again. Bill