Hi, this is Wayne again with a topic “Making Makey Part 3: Building the Molds”.
So welcome back in today’s episode of making makey we’re going to start making fiberglass molds it’s a horribly nasty toxic process, so i’m going to be wearing a respirator the whole time, and hopefully you can hear me well enough, but the object of the game is to Take these weird shapes that we’ve made the beginnings of this robot and actually make a negative version of them, essentially a hole, that’s the same shape and then we’ll fill that hole with something else to make a copy. That’S made out of fiberglass problem right now. Is models themselves all the prototypes are basically made out of mdf and bondo and garbage and they weigh about a half a hernia for those of you in a metric system. That’S a lot, so the idea is we’re going to make them out of something lighter and stronger and throw away the originals in the process. Gel coat is basically something that’s sandable and won’t deteriorate when it’s exposed to the sun. So it’s the same essential stuff. It’S another polyester product with some fillers added in to give it a little bit more body a little bit more viscosity, so it’ll make life easier as far as like trying to get it to cling to vertical surfaces.
That sort of thing in the case of the mold, we want to have something that we can. You know basically, polish out, make nice and smooth and strong. So we don’t have to worry about grinding into the actual fiberglass composite layup of the part would want to bond the two and we’re just going to blob this stuff on there, nice and thick again, you can see where the the pink part is. If i had a streak where i didn’t really hit it very well, because it’s a very different color, you can tell where there’s gaps in the coverage. Now, if i was painting i’d, be really upset with myself for all the brush strokes on the surface and all the thick spots and everything else, but in the case of the gel coat, what we’re doing is we’re actually putting on the outside first rather, the inside. In the case of a mold, basically the shape that it’s going on top of will determine the surface finish so by having that prototype piece all waxed and smooth, then, when we pop it out, the shape that’s left behind on the inside of the mold will also Be all shiny and smooth right so now the gel coat’s firmed up a little bit and it doesn’t actually stick when you poke at it, with your finger of course, when you’re waiting for that to happen, you don’t check by testing on the part, because it might Lift or cause some problems with the finish.
Instead, you go back to your mixing cup and wait until that stuff’s good and cured, and when you can finally get that stuff to not stick to things, you’re, probably good, to go to lay out fiberglass. On top of your parts, so tools of the trade we’ve got a mixing cup. We’Ve got a chip brush or china bristle brush, depending on who you ask, and i got a tongue depressor, because you need to mix it with something and then, of course, there’s also the polyester resin. Now for this, i’m gon na do one pint at a time.
For all you metric folks, a pints about half a liter, but honestly anybody over the age of 21 should know what a pint is, we’ll go ahead and decant just what we need for now. So now that we’ve got our mix go ahead and get the brush wet and we’re just going to coat over the gel coat, all our gray here, just to make sure everything’s wet with resin. Once we’ve got everything wet, then we’re going to start laying glass into it. Now it’s possible to just set the glass down and try to force the resin through it.
But i find this does a good job of guaranteeing that you don’t have as many bubbles trapped underneath the actual glass mat now, because we’re looking at a shape that has a lot of really weird little complex, curves and corners and ins and outs all over the Place the entire layup is going to be done with a three quarter. Ounce chopped strand mat, which i have a huge roll of directly over my head. So for the edges, i’m going to start by cutting strips off with a pair of scissors that i’ve sacrificed to the cause. These are my fiberglass and scissors you can tell by the ergonomic handles. We don’t need a bunch of extra fuzz hanging off the outside of the park, so we’re going to take our nice cut edge and lay that on the outside this stuff tears pretty easy just by pulling it apart with your fingers and again that outside edge is Going to be the flange where the parts get bolted together, so i’m going to start by doing a layer that just covers that just to guarantee it’s got a little extra thickness, so we get the whole flange covered with matte and then we’ll go back with our Brush wet it out and then force the resin into the mat along the way you’re going to notice this stuff is going to want to try to straighten out and be nice and flat and smooth. The object of the game is to get the resin forced in between all the strands and that’s going to help kind of break it up.
It’Ll kind of lubricate the space in between the fibers and then it’ll do a better job of conforming to the shape that we’ve got going here. The key thing here is making sure that you’re not overdoing it with the resin. You really want just enough for the glass fiber to be thoroughly saturated. You don’t want a big puddle anywhere, because that’s just extra weight.
That’S not really adding any strength to the final piece, so the fiberglass resin is actually a polyester resin and, unlike the stuff that you buy at the hardware store, this is fiberglass resin. It doesn’t want to cure on contact with air. So the thing is your hardware store, fiberglass resin will have a wax additive and, as the resin cures it that wax will rise to the surface and it’ll end up basically creating a barrier between the air and the polyester itself.
While it cures this stuff doesn’t have that wax additive, so it’ll take longer to cure, and it means that if i end up having some huge project that i don’t manage to finish all in one sitting, i can come back to it later and i still get A good chemical bond when i start laying up the next layer the downside to that is, if i don’t make it a point to add the wax additive to the very last layer, a lot of times, the fiberglass itself will remain tacky after it has cured. For quite a while, and you can solve that by basically painting it and then the paint becomes that barrier that eliminates the air contact with the surface. No one cared who i was before i started wearing the mask. So at this stage we’ve already made the first part of the mold which is now sitting face down on the table, which is nice. It means that the parts not going to get scratched up if we slide it around and we’re setting up parting wall for will be the second part of a three-part mold. The part that’s going to be interesting about this is we’re completely encasing it all the way around, so the mold is going to be completely covering the prototype and then once we’ve separated the parts for the mold. That’S when i’ll go ahead and cut a hole on this side and on the other side and that’ll be the access point.
That’S used to actually lay up material on the inside when it comes time to make the duplicate out of the mold. A lot of these things, you know the foot mold that we’re working on is going to be a one part mold, so it’ll be one piece it’ll just pop right out, just like a you know, seashell or a footprint or something you don’t have to worry about. The mold coming apart to get the part out in this case, since there was no good way to extract the part and still get all the details. We need on the sides that we need.
A better option is to make a mold that can be disassembled. So you don’t have to break anything to get the part out. The time has come to demold our foot prototype. This is the part where it’s going to turn out. The gel coat didn’t cure all the way through, maybe a little bit too much ask for it to just pop right out so mold. So again, we’re looking at the mold here and just to kind of explain this weird shape.
This is the foot and this is the outside of the mold, so it’s not exactly the same shape as the part’s going to be, but this portion of the bowl here is going to be what the shin piece rests on so we’ll have the possibility of an Ankle that can move left right front back as it angles, and it still has to be big enough for the wearer to be able to put their foot in and get strapped into the character’s foot. So now that we’ve got mold it’s time to clean out the release agent from the inside and then we’ll sand it smooth and then wax it and then put a coat of pva in there and then lay up the part, wet sanding lubricates the paper so that It doesn’t load up with stuff means that you don’t have to spend as much time throwing sandpaper away, and it’s usually the better answer when you start getting into finer grits. So i’m starting here with 320 grit, anything more aggressive than that and i’m likely to be changing the shape of the part as it stands right now. I’M just changing the surface finish, so we’ve got a few flaws from the pva, not being quite right.
Maybe a few flaws here and there from any issues with the gel or the paint that was on the original part and any issues with the gel coat layup that i did when i made the mold. So basically, this is just a quick polish everything up and make it look nice again and then, when we lay up the part, it’ll have the advantage of all of the cleanup work. I did on the prototype and additional cleanup work that was done to the mold.
Okay, so that’s the gist of how to make mold in fiberglass it’s something fairly simple, since we’ve got fairly simple shapes, we can get away with mold that doesn’t need to flex in order for the part to come out tune in next time and we’re going to Go through essentially the exact same process in reverse, to make a fiberglass part in the fiberglass mold. You .