3D printing with RepRap

This article was originally printed in Personal Computer World in 2008. I have reproduced it here as an adjunct to a new piece on the topic for RegHardware.

A staple of much science fiction is the universal machine – whether called a cornucopia, replicator, foundry or something else, it’s a familiar concept: a machine that can make anything, and at its extreme, more copies of itself. While a truly universal machine, able to create complex circuitry as easily as a cup of tea or a new swimsuit is still a dream, the idea of 3D printing is far from fiction.

In fact, ‘rapid prototyping’ machines are nothing new – they’ve been used in industry for some years now, enabling design drawings to be turned into objects by laying down successive very thin layers of plastic in a process a little like inkjet printing. But these machines cost thousands of pounds, and are very complex – certainly well out of the reach of the home or even small business user.

Now, though a lot of that could be set to change, thanks in large part to work that’s been carried out over the last few years at the University of Bath, creating a rapid prototyping device that?s not only a fraction of the cost of existing system, but can make many of its own parts and can be built and used without detailed specialist knowledge.

Rapid prototyping

The brainchild of Adrian Bowyer, RepRap stands for Replicating Rapid prototyper. The idea was first outlined in 2005, and the first RepRap built the following year. May of 2008 saw the ‘birth’ of the first child RepRap – one for which as many of the parts as possible were made on the original machine. But before we look at RepRap in more detail, exactly what is rapid prototyping, and how does it work?

Although we mentioned inkjet printing in the introduction, it’s perhaps more accurate to think about plotters; a rapid prototyper is based around an extruder – think of something like a glue gun, controlled by a computer – which is fed from a reel of plastic polymer. The polymer is heated and deposited on the surface below it. By moving the extruder head in the X and Y axes, it can create an outline, just like a plotter.

What makes things 3D is that the surface onto which the plastic is deposited can move up and down – the Z axis – and so by lowering it slightly after the first layer, another can be laid down, and so on, building up a three dimensional object.

The end result is a plastic version of the object, made using a polymer like PLA or ABS. But that’s not necessarily the end of things – not everything, for example, can really be made of plastic – especially those exposed to high temperatures. So in industrial or mechanical applications, the prototype that’s printed can then be used to create a mould, and an object then cast in metal or some or material. Since everything’s driven by computer, directly from drawings created in a CAD package, it can be far more accurate than making models and casting from them.

Introducing RepRap

Commercial rapid prototyping systems cost tens of thousands of pounds; RepRap’s different. It’s designed to be cheap to make, and the whole design – including the software – is open source. The intention is that anyone can put one together, and start making things.

The design is fairly simple, and even the extruder can be made without having to buy too many specialist parts. Items such as the stepper motors that are used to position the head are cheap, standard pieces, and everything’s controlled using standard microcontroller circuits, driven by open source software based on a system called Arduino, a cross platform toolset for linking your computer to the outside world.

The software on the PC drives RepRap, based on the design of an object which can be created in standard 3D design tools, and saved in a format called STL, which is used by many prototyping systems. There’s already a small and growing library of objects that you can download from the website; the project team hopes that in time more will be added, allowing people to create whatever they want, simply by downloading the object description and feeding the appropriate polymer into a RepRap machine.

If the idea is appealing, but the thought of building a machine from scratch is daunting, don’t worry – there are companies such as Bits From Bytes that can supply kits of the mechanical and electronic parts, so all you have to do is put them together.

All the software for RepRap is downloadable from the site, as well as comprehensive instructions. According to RepRap’s Adrian Bowyer, over 1,100 electronics kits have been sold, so there’s already a fairly large community of users.

Building a printer

Building your own 3D printer might seem odd, in these days where we buy new equipment rather than having old stuff repairs. But it’s probably not beyond the skills of most people who have built their own PC, and certainly not those who built their own computer, in the days before the IBM PC.

While RepRap is probably the most well known of the small prototyping systems, it’s not the only one. The Tommelise project at 3dreplicators.com is based on RepRap, but designed to be simpler and made out of wood, with just a few hand tools necessary to build it; the creators reckon it can be made for about $150 (£80).

Another project, Fab@Home is a little more expensive, with complete machines costing around $3,600 (£1,940). It uses a disposable syringe to deposit material, and can be modified to handle two at a time, enabling you to create more complex designs.

And, lest you think that you’ll only be able to build simple things like plastic cups, there are galleries on both the RepRap and the Fab@Home sites, showing some of the things that have been made by both machines – including screw top containers and even iPod covers.

If you simply want to experiment with what can be built by squeezing things out of a syringe, then Fab@Home is probably a little easier to get to grips, especially since you can buy a ready made machine while RepRap, with its polymer extruder, is arguably closer to a traditional rapid prototyping system and will require rather more effort to set up.

While much of what’s being made with RepRap at the moment is just polymer based, it won’t remain that way. Circuits can be included in designs by building small channels into them; RepRap’s Bowyer has created a second head for the system while is designed to lay down track of Field’s Metal – an alloy with a very low melting point – in those channels. That can provide the internal wiring to link components. By including appropriately shaped compartments for things like integrated circuits, they can be dropped in place, making contact with the tracks laid down by the printer.

Similar techniques have been used with Fab@Home too, with conductive pastes laid on the other materials, and it’s this that has enabled users to come up with basic electric designs, such as simple miniature torches, linking batteries to LEDs. Although it’s still relatively early days – the ‘print head’ for Field’s Metal hasn’t yet been integrated into the RepRap, techniques like these will make such 3D printers even more versatile.

One we made earlier

One of the novel things about RepRap – and the reason for the ‘Rep’ part of the name – is that a functioning machine can make all the plastic parts for another one; in fact, the ability to create a copy of itself was one of the main design objective. So whether you’ve bought a kit or made one from scratch, you can set it making spares as soon as you’ve finished it. Or create another to give to someone else.

Of course, with the need to use some parts that can’t be easily replicated, such as the metal connecting roads, wires and the programmable microcontrollers, RepRap and similar systems are in reality a long way from the cornucopia machines of science fiction. But that’s not to say that they can’t have a dramatic effect – especially if, as we mention in the box out, they use as their source material things that can be grown and turned into a polymer without industrial scale processes.

Look around and see how many simple plastic objects – or objects that can be made of plastic – we use every day; combs, cutlery, crockery, containers, valves and so on. Being able to make those cheaply and easily with a computer, a 3D printer and locally grown supplies really could make a difference to a lot of people. RepRap’s slogan is ‘Wealth without money.’ And why bother printing money, when you can print the things you’d use it to buy?

 
 
 
March 2011
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