In this chapter of the Zero to Maker workshop, we're looking at moulding and casting, a creative way to make specialty parts for your project. If you're new to this workshop, we'll be taking you on a fast-paced and practical journey to learn a wide variety of maker skills so that you have the tools and knowledge to make anything. So follow along as we develop our own projects and share insights into the process. So far we've covered a fair few ways to make parts, and this week we'll be adding another tool to your maker toolbox with moulding and casting. Now this can be a bit of a broad category and includes things like injection moulding and casting metals into sand moulds, but we'll be taking a look at the more accessible at-home version of making silicon moulds to cast resin and other materials.

I'm going to be waterproofing my soil moisture sensors by casting them in resin. And now mine seems really lame because he's doing something cool and like waterproofing electronics and I'm making an end cap that can be easily 3D printed, but it's just a test for the whole process and see how it goes. So first things first, we need a mould. Now you can buy a whole range of weird and wacky moulds online, and if you've ever wanted to make dice, this is a really good opportunity. But for us makers, we'll probably need to make our own custom silicon moulds. And to do that, we're going to need a primary mould. This is a mould that we pour silicon into to make the silicon mould itself. We made ours using this very fancy milling machine, but you can also 3D print your own. And of course, we need a 3D model for this, which is a little tricky to wrap your head around what exactly we need to model, because the silicon needs to be the negative of the part you want to make. And this needs to be the negative of the silicon mould. So you need to model negative of the negative, which ends up just being the part you want, plus some walls to keep the silicon in.

So we exported our model and cut it out of a big old block of jeweler's wax. Now if you don't have a $7,000 precision milling machine lying around, check out your local fab lab or makerspace, because chances are they probably will have one. And if you don't want to do that, you can always 3D print your own primary mould. We did a test one here and it worked out perfectly fine. But because the primary mould has print lines, the silicon mould will have print lines, and the final part will also have print lines, which might be a deal breaker. But you could always sand down or smooth your primary mould first, or use a resin printer which has barely visible layer lines, but all of that is a rabbit hole in and of itself. Just remember, if you're going to make thousands of parts from this primary mould, it might be worth the time making it nice.

So we have our primary mould. From here it's a super easy process. First we're going to add a release agent to the mould so the silicon doesn't stick. We just use a little bit of Vaseline. And then we mix up some two-part silicon and pour it in, making sure to get it into every crevasse. Then after a few hours of curing, we popped it out and look how smooth it came out. The milling machine took a few hours to make this primary mould, but this silicon mould that came out of it is smoother than I could print on even a resin printer. And obviously our printed one came out with some layer lines, but it's pretty serviceable. And if you don't really care about the layer lines, then it's definitely very usable. Absolutely.

Now there are lots of materials that we can cast into this silicon mould. We're just using UV resin, so it hardens in just a few minutes with just sunlight. And of course, resin is toxic and hazardous. So use it in a ventilated area, wear gloves, avoid contact with it, use safety glasses and keep your area clean. Now for my parts, I just mixed in some purple dye for my first batch and some UV fluorescent dye for the second batch. What the... Oh no! I cured them in our UV curing station. Sunlight will also do. And that was it. It's pretty straightforward to make patches. And I did get some bubbles in my first batch, but my second one, I left the resin a little bit longer before pouring, which really helped. And for us, it didn't really matter, but these top bubbles can be fixed with a quick heat of a blow torch. Or if you're really pedantic, you could use a vacuum chamber, which completely eliminates all the bubbles.

And these turned out pretty well. They are simple parts that can be easily 3D printed, but it was a good little test run of the whole process. And as you can see, my parts fluoresce when exposed to UV light, which is a very cool feature. For my part, I cut a hole in my mould, inserted my moisture sensor, and did basically the same thing. Once the resin had cured, I had a beautiful and waterproofed part. There are a lot of other ways to do this. Some might be a lot easier. This was a fun little experiment. And we also made this little pot with a 3D printed mould. And you can see those layer lines coming through. This was a very fast print with large layer lines, but all things considered, it's pretty good. And using that exact same mould, we also made this little one with plaster of Paris. And this came out pretty nice as well. It looks basically identical to that one, but made out of plaster. Ah, I dropped the spoon into the plaster.

And this is something that might interest a lot of makers because this part won't break down in sunlight like a 3D printed part might. And it's extremely heat resistant. This can easily handle up to probably 500-degrees. Now, not every project will need a part rated to 500-degrees, but it's great to operate with these kind of tools to get these specific properties out of the pot. So we've already looked at other manufacturing techniques like 3D printing, laser cutting, CNC machining. Why would we need to make something with this? What's our motivations? Well, casting and moulding lies in a bit of a niche spot. Much of my robot is 3D printed and laser cut. But if I were to instead make them out of resin, it would take far longer and it would probably take a lot more of my time and would be way more expensive. And it's a very similar story for the enclosures of my plant monitoring system.

So what parts would you cast? Well, let's look at all the benefits and know why and when we would use it. First of all, you can make a lot of things very quickly. If I wanted to make a thousand of these end caps here, it would probably be quicker to cast them. And another advantage is that the parts are pretty identical. The same mould, you can make nearly the same part every time. No print defects or inconsistencies if you have a good casting setup. The parts you can make with this are also very detailed. If your silicon mould has intricate details, the resin part you make with that mould will have that beautiful and intricate detail. It's also possible to make clear parts. 3D printers really struggle with that and resin doesn't have the multiple layers and lines. It's one big chunk of plastic and it can be super clear. But possibly the most advantageous to us makers is the ability to get creative with the process.

Your design and ideas stem from the tools that you use. And I've had so many ideas for cool projects now that I have this tool available. Heat-resistant insulation tiles, experimenting with conductive parts by maybe mixing in graphene and even making some soft robotics by casting the silicon itself into 3D printed moulds. And even making some composite materials. Similar to Mythbusters, you can embed 3D printed bones into a cast of a gelatin hand. Fibers in ceramics make them stronger or taking embedded sensors in electronics to the next level. Is there a reason why we couldn't put a light sensor inside of clear resin to waterproof it? Well, that was a great little look into the world of moulding and casting and I would definitely recommend this process. At least just try it for the very fun of it. It was one of the best weeks of Fab Academy and it was really rewarding to just make something and it really is a method that has lots of room for creativity just from the nature of how you make the parts. So I hope that also gave you another process in your maker toolbox. And for sure we'll see you next time. I completely forgot I had to deliver as well.