Rotational moulding

Do you know how you make a ball pit at the playground? You fill up a hole with a bunch of little balls, right?

Well, making things out of plastic can be a bit like that, except instead of filling up a hole with balls, we fill up a big mold with melted plastic. This process is called rotational moulding.

Imagine you have a big plastic container shaped like a ball. We'll call it a "mould." We start by heating up some plastic pellets until they melt into a gooey liquid. Then, we pour that liquid into the mould.

Now, this is where things get interesting. We're going to spin the mould around and around! This is sort of like how you spin around in circles in the playground. As the mould turns, the liquid plastic sloshes around inside, coating every surface evenly. It's kind of like we're using the force of the spinning to evenly cover everything inside the mould.

After a while, we stop spinning the mould and let the plastic cool down. Once the plastic hardens, we pop open the mould...ta-dah! We've got a newly-minted plastic ball!

Rotational moulding is really handy for making big, hollow objects like tanks, kayaks, and playground equipment. Because the melted plastic is evenly distributed by the spinning, these objects are often very sturdy and strong. Plus, because the moulds can be made in lots of different shapes and sizes, we can make lots of different things using rotational moulding.