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When I make up my pattern for the mold, after I get it nice and smooth with sanding and body filler, what do I coat it with as the final step before making the mold? In my search online it seems like patterns are finished with some type of coating that looks like paint to me, then polished and a release agent is applied prior to beginning the process of making the mold. Of course those specialty coatings are more spendy than just say spray paint. Do I HAVE to use a specialty coating or can I get away with something else?
I've made more than a few molds (and bucks) using black spray paint as the final coating. Black works nicely as it allows you see where there are air bubbles during your layup. Just make sure to use a non liquid wax as a release agent, apply it in at least three coats to be sure you covered the entire surface. Waxing surfaces exterior the mold surface is good too, it helps release any drips and over runs that might occur. This process works well if the mold is only going to be used occasionally, but if you wish to make a lot of parts you are better off using other methods.
It's going to be a one time mold and I was going to use gel coat on the actual mold itself that I use to make the final part from. I was more asking what to use as the final coat on the pattern or plug that I make to take the mold off of. I just was trying to avoid the unnecessary expense of a specialty coating if it wasn't really needed. I recently found a video where they used several coats of epoxy primer that was sanded down to 600 then polished as the final coat on pattern, I'm going to give that a shot. Or black paint as Sav0r mentioned
I always use high build primer, get it nicely sanded, then throw down three or four coats of black. I like to wet sand in between coats. Once it's a nice finish just let it cure, wax it up, and go to town. It's always worked very well for me.
I always use high build primer, get it nicely sanded, then throw down three or four coats of black. I like to wet sand in between coats. Once it's a nice finish just let it cure, wax it up, and go to town. It's always worked very well for me.
That's all true J-Rod for production molds, but for a one off, it's not really necessary.
On a one off part, the mold needs to be as smooth as you can get it - within reason. You can always wet sand the finished part to remove any minor surface imperfections.
That said, for pulling shiny carbon fiber parts out, the mold should be as good as you can get it. You don't want to risk rubbing through to the carbon weave. And let's not forget that CF parts are usually clear coated for that extra shine. If you are planning on painting the part, it's a whole lot less of an issue.
And if it's a seat and completely covered, it doesn't matter much at all.
I usually go 600 grit. But as Teazer talked about, I painted my pieces after, so I wasn't necessarily in need of a perfect finish. You'll have to decide what you want and then go from there.
I will be clearing one piece and painting the other, so no, the molds won't have to be perfect. I just want the pieces to come out with as little smoothing and finish work as possible.
Thanks for all the input guys! This is my first time making a mold and using carbon and I know a lot of steps on manufacturers sites and on the interweb aren't necessarily necessary if I'm only doing one part, so I'm going to you guys because you all have "real" world experience.
Hobbyists get away with a lot of stuff that a production facility wouldn't. The proper products recommended by the manufacturers are the absolute right way to go, however you can cheat that if you expect less performance, different performance, possible interactions, etc etc.
IE you can use hairspray instead of PVA to get parts to release. You can spraypaint a plug instead of using Duratec finishing primer.
The money on special components doesn't pay for itself unless you do it over and over.
I regards to the pattern/plug for the mold, what weight chopped strand mat and how many layers? What weight and how many layers of cloth? Those who do it, what's your process?
Same question for the mold, what weight and how many layers? Should I only use cloth for the mold or add some csm as well? I've also read that the mold should be at least 3 or 4 time the thickness of the final part, is that accurate?
I use hairspray as release. It works well, you just have to get decent hairspray and then let water evaporate off. It's probably overboard though. A good waxing usually is more than enough.
For molds or plugs, basically anything that doesn't need to be light and strong, I use mat. I just use the cheapest mat I can get my hands on really. Generally my plugs and molds are very resin heavy, so I tend to use cheaper polyester resins. I find dense is good. I use a big set of scissors to cut the mat as I go. Get some invisible gloves cream and use it liberally. It makes working with this stuff a million times more bearable.
For the actual part, I always use cloth and epoxy resin. The number of layers, type of cloth, and orientation of the ply depends on the type of part.
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