The almost unsuccessful - successful mold

2 weeks, 4 kilos of resin, many yards of fiberglass, and 5 stiches!!!

thats how much it cost me to build this two-piece front spoiler mold for the toyota starlet glanza ('96)

it’s a very rare spoiler cause it was offered only as a dealer extra in japan, and does not exist as a part. so, since i was in possession of one, i had to make a mold (my real plan was to have a backup, and make a new one from carbon for myself)

i first sent the spoiler to be painted by my friend who is a pro, and he did a wonderful job… then me and another friend built the two piece mold. I used metal sheets to make the flange around the part, and just when we would begin demolding, there was one piece of metal left inside… i was pulling it out when my mate said “leave it for later man, help me here a bit” so i did, and later when my hand passed through the mold, i was slashed to the bone. we spent the rest of the night at the hospital getting stiched and shot with anti tetanic shots etc. lots of fun, lets do it again sometime.:cool:

ANYWAY, i’m getting to the point… the spoiler as i said was painted like a normal car part… in a spray booth, color and clear coat. it sat for a month before we started the mold. I used meguiars wax as a release agent, about 4-5 times… when we finally demolded it, the paint had stuck in the mold, leaving at places only bare plastic to the spoiler… :eek:

generally i have very nice results with meguiars wax, i dont know why the gelcoat bonded so well with the paint… any ideas? i’m not gonna throw away the mold, im gonna sand it down and polish it…

here’s a pic of the outside, i havent taken pics of the inside yet… i will though.

this is the spoiler in case you’re curious

sorry to hear it end like that, but hopefully you will be able to salvage the mold.

Any time I make a mold I am sure to use PVA on the plug, I am not too confident in a wax alone.

How long did you leave the layers of wax to dry before buffing?

You might have better luck with TR high temp release wax.

Waste of time. Wax is so much better than PVA. Not to mention the crappy texture it leaves.

Was the plug sealed before apply the mold release?

I just dont’ have faith in wax alone… I have never had a part stick using pva. I spray it very fine and very little at a time. I get a very shiny translucent surface with virtually no orange peel looking stuff going on.

Sometimes wax alone won’t do in my situation, for example when I have some gaps that I have filled with plasticine, rubbing wax over it might not be so good.

perhaps I will try wax alone on some simple plugs to see how it works for me.

what do you mean sealed? i have a sort of pva, but doesnt work for a spray gun (makes tiny bubbles)…i have to get a pva that i can spray on in thin layers to get a nice surface…

1: Sperm. release agent, like Frekot or Safe-lease!!!
2: Yeah, I almost feel your pain. Scraping thin flaskbreaker off some ceramic tiles, it jumped and ran into my thumb. No stitches, but I doubt I won’t take a bandaid off for at least 3 weeks.
3: Really. I’ve had 4 x 6 foot Cynate Ester parts fall off the mold using Hysol (or loctite, or whoever they are) Frekot. We use 700 and 55NC.

55 dries in a few min to recoat, 700NC takes a bit more time, and smells worse.

and another thing… lately i’ve been using AEROFIX , its a spray glue for composites, to fix cloth into the molds. now THAT makes demolding a real bitch!

do the solvents in the releases not attack the plastics of some plugs?

First problem- you didn’t wax enough to get every single sq centimeter of the painted surface covered in wax. When you are waxing, you’re not building successively thicker coats you do it that many times to make sure every sq-cm is covered and protected. I preffer to apply 7-8 coats over a two day period on any plug and thinned PVA that might be a problem or is a cusomers peice that I’m using.

the paint had stuck in the mold, leaving at places only bare plastic to the spoiler…

Second problem- even with adhesion promoter for plastics, paint has a HORRIBLE time sticking to it. It would much rather stick to gelcoat :frowning: :wink:
Should have used PVA or a semi release, actually you kinda did with the fresh paint. sorry I had to ;):eek:

generally i have very nice results with meguiars wax, i dont know why the gelcoat bonded so well with the paint… any ideas? i’m not gonna throw away the mold, im gonna sand it down and polish it…

Save the mold, make FG part from it (including flanges) finish this as a proper plug and make a new mold from this newly improved plug. Yeah its alot of extra work but it might be easier than repairing the current mold and you’ll have a spare plug to use should you ever want to make a new mold.

OR for all I know you might just be able to use some laquer thinner to dissolve the paint on the surface and polish it up.

bummer you had so many problems with the bumper and mold. Did the painter use any Bulldog or other brand of adhesion promoter before he primered and painted the bumper?

Also on painted parts it’s best to wet sand and buff to a high gloss before making the plug itself. This gets rid of any surface contaminants like dust nibs and orange peel from the paint. Plus you’ll have a mirror smooth mold after.

I’m fairly new to composites but i can agree with 20_rc51_00 because i dont’ use semi-perm mold release agents… i use pva and it does leave a slight orange peelish texture for me, but i like it anyhow for now since i’m on a budget.

Semi Perms i would like to try later, like after i have all 20 of these molds made that i need.

me and my friend busted our elbows sanding down the two pieces of the mold. its not perfect, but its smooth now. i made do with whatever i had in hand, which means 240, 320, 600, 1200, 1500 and 2000 sandpaper, a hand polish with a thick polishing compound and several layers of wax. then , the usual. gelcoat, thin woven fg to take the wierd curves and surfaces, then thicker (290 gr/m) woven glass… since the original spoiler is really thick plastic, around 2mm , i can go thick with my materials without fear of bad fitment. so im gonna go for 6-7 layers of 290gr glass, for strength. (im going out of topic but hey :D)

i hope it releases ok, mainly not doing any damage to the mold…

well, let’s call it a success :). I know it’s only fiberglass but i’m proud of it. Next one will be made with black gelcoat, and i’m thinking epoxy on woven roving, and then overlaid with carbon (because when the two halves of the mould are joined, its impossible to put your hand and do any work…

Good work aga,

don’t worry I see ur going very well. keep going. :wink:

Looking good. Nothing wrong with fiberglass. If I were into making car parts I would use 6781 over carbon any day of the week. Its much cheaper, kind of strong, and only slightly heavier.

Keep up the good work, and more importantly post more pics!

thanks guys :smiley:

Nice!
Any pics of the mold?

i will take some if you want :slight_smile:

Yes, please do!

here are the two pieces of the mold, the gray stuff etc you see are primer and some paint from the plug, it was a disaster, the paint was pulled off in places and stuck inside the mold… we sanded it down and polished it by hand as much as we could… after the two first products made, the materials stuck inside kept coming off requiring more sanding and polishing… so enough is enough, i’m using priming wax and pva for the next one, im sick of sanding… the product is gonna be primered anyway…

after a few parts and well waxed the mold will be properly broken in and you won’t have to use PVA everytime.

well done though looks very good