We don't how many RepRap 3D printers are in existence, and that's because everyone who owns a RepRap can use it to make another - and another, and another. The RepRap's creator, Adrian Bowyer, designed it to be self-replicating. We sat down with him to talk about the international community of enthusiasts that brought RepRap to fruition, and how open-source hardware can help propel a low-cost design to popularity and world domination.

TechRadar: How did RepRap start?

Adrian Bowyer: I've always been interested in the idea of an artificial, self-replicating machine. As a child, it seemed obvious to me that human beings don't make things in the right way.

Plants make things in the most efficient way. The plant is a self-replicating object, entirely composed of self-replicating cells. So if you want to make things, you start with things that can make themselves. That's the basis of what was going on in my mind.

I bought a couple of 3D printers. They were big commercial machines - the only type available then - and the cheapest one was worth £250,000. We started using them, and found them to be a very useful resource.

The 3D printers that print themselves: how RepRap will change the world
Adrian Bowyer is the man behind RepRap

As an engineer, it was complete liberation. I could just think of something, design it and have it in my hand. It also occurred to me that we had a technology that was versatile enough to replicate itself. That's where the idea "we'll make a 3D printer that prints itself" came from.

I realised we had to make this open source. This is because if you have a self-replicating machine and try to close it off and copyright it, you're basically saying you're trying to stop the one thing that you designed the machine to do.

TR: How long was it from the initial start to having a working printer?

AB: Work actually started in 2005 and we had our first functioning machine two years later in 2007. A year later, that machine had printed 
a complete set of parts to make a copy of itself.

Obviously, there were tweaks and changes along the way. We made the very first copy in May 2008. Therefore, by that point we'd reached a partially self-replicating printer.

We never thought from the beginning it would be able to print 100% of itself. The idea was to print all the fiddly pieces and make sure all the other bits required to make the machine were widely available. It's about 50/50 - 50% printed parts and 50% bought parts. We've got the specialist parts down to just one or two.

The 3D printers that print themselves: how RepRap will change the world
The first object printed with a RepRap was a coat hook

TR: What was the first thing that you printed?

AB: One of the very first things we printed was a coat hook. An economist once told me that the world market for coat hooks is bigger than that of jet engines. When you think about it, it isn't that surprising - it's just you never think of coat hooks as being major engineering products in the same way as jet engines.

TR: And that model could be uploaded?

AB: We did upload it, so anyone who wants to print that part can. The whole law of intellectual property is quite interesting. If you're Ford or whoever, you can't patent a bonnet latch like an idea.

You can patent the design, but that just stops people copying the computer files - they can't stop you copying the object. You can't copyright a 3D object unless it's a sculpture.

TR: Do you see this causing changes in the law further down the line?

AB: That's difficult to say - how would it be policed? We have copyright for music and it's effectively ignored by millions of human beings. So if you try and pass a law that makes what everyone does in the privacy of their own home an offence, it's never going to work.