Hi, this is Wayne again with a topic “Building Up To Maker Faire: Shawn Thorsson’s ED-209- Part 3”.
Hi my name’s Sean Thorson. I make props and costumes for all sorts of different applications and this year to get ready for the Maker Faire, I’m building the giant bad guy robot from the original Robocop movies called ed-209. It’S going to be everything I can do to get it done just in time for the event, and here we go last time we were here, we covered fiberglass mold making. So, in the meantime, I’ve made the mold for the shin, and you can see here the second piece of the lower leg second copy rather coming out of the mold.
These will be getting a little bit of body shop work here pretty soon and once the seams are smoothed out, they’ll be ready to prep for paint. We also made this mold for the heel block. The last time you were here got the prototype for the gun. Pod starting to shape up here, it still needs a tiny little bit more smoothing and filling once the wood grain is all painted in and filled it’ll, be ready for molding and kicking around the rail that runs up and down on the back of the leg. For a while now this is gon na be vacuum formed we’ll cover that next episode on the top of the rail there’s a cap, so this portion will actually probably be done in fiberglass.
There’S still a couple more details to work out on the top end of this part before it’s gon na be ready for molding on the side of the shin or a lower leg is a little detail panel. This part is gon na, be cast separately and insert it into the recess on the side of the leg. We’Ve got the first of the toes starting to shape up here. So this piece once it’s all finished, it still needs a little bit more filling and sanding.
Then it’s going to get primed painted once it’s shining we’ll be able to go ahead and pull a mold off of that got a small detail, that’s going to be cast separately and attach to the five portion where the hydraulic rams attach, just above the ankle joint. This piece here is one of the details that goes on the side of the ammo box for the gun pod. It’S going to be cast separately again, all right. So last time we were here, we covered fiberglass, mold, making and fiberglass casting this time around. I’M gon na go over silicone mold, making silicones ideal for small details where fiberglass is really great for inexpensively reproducing fairly big parts that are lightweight. Silicone is great for picking up really tiny details.
It also has the advantage that it doesn’t stick to anything. So, unlike the fiberglass mold making process we went through before, we won’t need to worry about using any kind of a release agent in order to pull the pieces out of the molds. One of the main reasons for making a mold is, if you’ve got one thing.
One prototype one sculpt one piece of hardware that you want to reproduce: you can get away with making lots of copies out of something that’s lighter and cheaper, as opposed to having to go through and sculpt or machine or manufacture. The same part over and over again using the same process in this case, one of the things that’s recurring detail over the entire body of the robot. Are these little socket head screws? Now this particular piece of hardware, the smallest one of these, I could find in the right diameter – still costs about 3 or 4 dollars.
Now, when you consider the fact that I’m gon na need 160 of these things littered over the entire character, it’s gon na start to stack up pretty quick, and I really don’t wan na spend that kind of money on bolts, not to mention the added weight. So, in order to get this detail, looking just exactly like this, I’m gon na go ahead and make plastic copies that are gon na, be a lot less expensive. So, just to give you an idea of what we’re looking at a mold is basically a hole. That’S the same shape as the piece you’re trying to reproduce so a while back. I went ahead and made this part right. This is a little detail that goes on the side of the heel block and we need two of them for each legs.
We’Re gon na need four total and all the time spent on the scroll saw cutting out all these layers of plastic and MDF and stacking them up are time-consuming and then more to the point. It’S basically made out of garbage. So it’s not gon na hold up too well to any kind of abuse or knocking around in order to make it weigh less and whether better I want to make it out of something else. So what I ended up doing was I build this rubber block. Silicone rubber and it was made by pouring it over the top of this piece. Once this is finished, we go ahead and peel off the rubber part and then pour plastic into it.
In this case, I’m using a urethane resin, you mix the two parts fill up. The mold it cures after a few minutes. You pop out the piece and the piece that comes out has every single detail that the original piece had down to even fingerprints in the paint. If you made that kind of mistake.
So since we’ve got, you know 180 or so of these little socket cap screws all over this character. The deal is rather than make my fiberglass molds, with a recess. That’S already set up with a socket screw inside there’s something that’s going to be very likely to trap itself in the mold and break something in the course of separation. What I did was, I just went ahead and made all these surfaces smooth. Now, there’s a lot of little details on the side here, where you’ve got all these screws that mount in and there’s recessed holes that the screws go into.
So what I’m gon na do is actually cut a hole and then make a separate piece that I can insert from the inside into that hole. That’Ll actually end up faking our little screw detail. Alright. So here’s my original piece: what we’re gon na call the prototype when you’re building a prototype, you want to be really careful about making sure that you don’t leave any flaws that you don’t want to have in every single piece. There are certain medical applications where they use types of silicone rubber to actually replicate cell structures. So if you’ve got a tiny little scratch that you don’t want to have to fix every single time, you make a copy of your part. You want to go ahead and fix it in the prototype stage. In this case, it’s a fairly rough part, so we’re not going to have to go too crazy, getting details just right, but what we’re gon na do is we’re gon na build an enclosure, basically a mold box that we can fill up with silicone rubber and then Set aside, while it cures, so the mold box needs to be big enough, that we can get about a half an inch worth of material all the way around the piece in this case we’re making what’s called a block mold, it’s basically just gon na, be a Block of rubber with a hole in it the same shape as our original prototype, so I’m gon na go ahead and I’m gon na mark out on this piece of cardboard here, which is white on white for horrible contrast, a rough size of our original part. Then I’m gon na take another piece of cardboard and I’m gon na build a wall around it with, like. I say that half-inch standoff now, when I’m building a wall, I’m gon na use a CA. Adhesive stands for cyanoacrylate, it’s basically super glue and I’m just gon na go ahead and fill along this seam all the way along the bottom, and then I use this accelerating agent, occasionally called zip kicker to just cure. It basically flashes it right. Now, all of a sudden, the glue is dry continuing all the way around again.
The object of the game is to make this little box so that it’s completely watertight pay special attention on a vertical seam here and now I’m gon na go ahead and do it on the inside as well again, just to make sure just give us a little Bit more insurance that it’s actually gon na be watertight. So now I’ve made an arguably watertight box: we’re gon na go ahead and put a dab of glue on the bottom of the prototype and then Center it up in the bottom of the box. Reason for the glue if you’ve got a lightweight prototype, you want to keep it from floating away in the silicone, but in this case it’s nice and heavy. We just want to make sure that as we’re pouring the silicone in the part doesn’t shift towards one of the walls of the mold box and get a thin spot on one side where the mold will sag and possibly leak or tear easily. Now the silicone that we’re mixing it mixes by weight. In this case, you can find silicones that mix by volume, usually they’re gon na be a little less expensive or and probably a little bit shorter lived.
So your molds aren’t gon na be able to generate quite as many castings, but what we’re gon na do now that I’ve cleaned off my mixer mm- go ahead and turn on my scale here, and since this is a 50-pound bucket or rubber, I don’t want to Have to lift it and hold it there while I’m pouring, so I cheat a little bit now. We only need just enough silicone to fill up our mold box that we’ve already made I’m gon na guess it’s probably gon na be about four or five fluid ounces. That’S just a volume measurement, of course, we’re in the Imperial system, so fluid ounces and weights not going to have any relation whatsoever. So we’re going to take the catalyst here. We’Ve got just shy of 6 ounces of material here.
So I need point. Six ounces of catalyst there we go all right, so we have our 10 to 1 mix already poured. We can set the scale aside now and go ahead and mix.
So mechanical mixing is probably a bad idea, but I’m impatient so I do it anyway, as I’m mixing you’re gon na notice, I’m gon na be using the mixing head to scrape the material off the sides of the cup so that it’s blended evenly all right. Once it’s all one color we’re ready to pour and the trick is you want to pour it into one of the corners? You can actually tip the box up just a little bit. You don’t want to pour right on top of the actual prototype, because what’s gon na happen is it’ll trap bubbles underneath. So what we’re looking for is to just go ahead and get a little bit of the stream pouring out into one of the corners in the mold box along the edge down into the bottom. So it’s not actually on the part and I’m gon na go ahead and lift this as I’m pouring it. It’S gon na draw it into a really thin strand, so any of the bubbles that I’ve mixed into the silicone will end up rupturing on the way down into the mold box. Now, as I’m doing this, it’s gon na slowly start overflowing the top of my part. There and again it’s gon na, be basically the silicone is gon na be spreading up at it from underneath, and you want to go ahead and fill the mold until it’s about 1/2 an inch above your original part.
Now, in this case, I’ve got lots of neat little marks on the insides of the cardboard there that make it easy to pick out where that 1/2 inch above the park is. But if you don’t it’s a good, go ahead and use a sharpie or a pencil and actually give yourself a mark so that you know when you can stop pouring nice part about silicone rubber and the reason it’s ideal for mold making is because it doesn’t stick To anything, so, unlike the fiberglass mold making process, I went through last time. We aren’t gon na have to worry about a mold release agent, so the prototype once this is cured, prototypes, going to slide right out with no problems and each of the castings that we make once they cure. They’Re gon na slide right out with no problems.
All right, so it’s gon na take the silicone anywhere from 12 to 24 hours to cure. That depends on the brand and how you mix it and everything else, rather than sit and wait for the part that I just poured the mold for to actually cure. I’M gon na go ahead and open up this mold that I already made yesterday, so this mold box was made in the exact same way it’s just a piece of cardboard, wrapped around and glued until it’s watertight and filled with silicone rubber. In this case, this is just the head for the socket cap screw like I had before. This is where the piece went in on the bottom, and there is our prototype. So now I’m gon na clean up this little bit of silicone. That’S hanging off the edges here in this case I mounted this guy on a little bit of clay so that I’ve got some extra material that I’ll end up casting, which can then be cut off. So I don’t have to worry about having bubbles in the part itself, so there’s the mold, so the actual castings out of the silicone mold are gon na be made with a urethane casting resin. It’S a two-part plastic. You mix two liquids by volume and once they’re mixed together, you get about five or ten minutes before they start to turn solid in about 20 minutes later, you can actually pull a solid plastic piece out of the mold.
I’M gon na be adding a pigment, the resin that I’m using will cure to a bone white color. If you don’t so, I’m gon na be adding a black pigment to make it a little bit of a darker gray, so that if the paint gets scratched, the parts will be a little bit more believable than white plastic right. So the actual missing mixing process very straightforward, we’ve got Part A Part B. It doesn’t really matter which order I mix them in, but I’m going to start by putting about 3/4 of an ounce of Part A and then another 3/4 of an ounce for a total of one and a half ounces.
This is Part B and then I’m going to go ahead and add a drop or two of black pigment use. Another tongue depressor go ahead and mix this up. You want to get all the material evenly mixed, I’m going to scrape the sides of the cup in the process and then it’s just a question of pouring it into the mold. We’Ll give that another couple of minutes it’ll start to turn solid and then we’ll be able to go ahead and pop it out of the mold and we’ll have an exact duplicate of the original piece, except in plastic, all right. So after a few minutes, the resin cures you can tell because it changes color. We went from our nice dark black that we had before to a much lighter gray, but now we’re ready to go ahead and pull the part out of the mold and just kind of get a grip on there.
There’S our casting next to the prototype same thing. With this other mold, we poured there’s their casting and there’s the original prototype didn’t bother, making it as tall, because there’s no reason to waste all this extra plastic. When we really just need the top face, and if you take a closer look like I mentioned, you can see maker’s mark just like I said, you’ve got the original stamp on the top and all of knurling lines on the side. So that’s a quick and dirty version of how to make silicone rubber molds for urethane casting tune in next time.
I’M gon na be going over how to make vacuum. Forming bucks and replicate parts in lightweight plastic be sure to check it out. You .