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The Glitch

06 May 201404:54AM3d-printing

So here's something you don't see every day:

a glitch in the matrix?

This is what happens when a 3D printer like the ones we have at Scitech has a glitch. And as cool as I find 3D printers when they're working properly, I think the way they mess up is even more fascinating.

I think the reason why is that it's such a uniquely digital way of messing up. It almost reminds me of screen tearing, or some of the stranger geometry and physics bugs you see in video games. See, usually manufacturing defects happen because of hardware, because somewhere in the circuitous analog process of material processing, manufacturing, assembling and shipping something has gone slightly awry, resulting in a broken product. But these aren't broken. As far as the actual materials and assembly process is concerned, these are manufactured perfectly. It's just that they're manufactured perfectly wrong. It's a software glitch made physical.

Like any glitch, this one is great at exposing messy, fascinating inside workings. For example, this is excellent evidence that devices like the MakerBot have no error correction, or indeed any external sensors to do it with. They works entirely off their own internal model of the universe, and when that internal model doesn't match up with reality, they keeps going regardless - not because they don't care, but because they can't even tell that there's a problem*.

Teaching a computer to use the kind of constant sensory feedback data that we get as humans is not only hard and computationally very expensive, it also almost certainly won't get good results. Which is not to say that it's impossible - just that you would massively increase the cost and complexity of your printer for a pretty dubious advantage. On the other hand, computers are fantastic at remembering and executing long lists of instructions - in this case, where to put your printer head and when to ooze plastic goop - without much context or feedback, and compared with how humans handle the same task, they do an exceptional job. Which now that I think about it, is probably why GPS navigation systems are so popular, even if they are occasionally frustrating and illogical for exactly the same reason.

considerably less delicious than actual honeycomb.

You can also see the internal structure of 3D printed objects, which is this neat sort of honeycomb thing. It doesn't always choose honeycomb - if you print something square it does a rectangular lattice instead. It often surprises people that they aren't either solid or hollow inside, and while you can change the slider to either extreme, the best results are somewhere in the middle. I guess that's not something you see very often in ordinary plastic manufacturing.

(When the inevitable "I heard you can use these to make guns" comes up, this is what I pull out. As strong as this kind of latticework is, you'd have to be an idiot to fire a bullet out of it.)

not as tasty as real spaghetti.

This particular glitch also shows one of the major limitations of 3D printing - that because it's what's called "additive manufacturing", every layer has to be printed on top of the last. This means that objects with overhangs can't be printed, because otherwise you end up with what we've taken to calling 'spaghetti' - those weird looking tentacley things hanging off the displaced sections of the rockets, where there hasn't been anything for that layer of plastic to sit on. Usually the software will try to work around this by printing supports (which you can remove later) on any angle over about a couple of degrees so ideally, you'd never even notice - but because these guys were never meant to have overhangs in the first place, it's quite a neat illustration of what happens when you don't have supports and why the software might add them in the first place.

I guess as 3D printing gets more commonplace we'll get used to this kind of thing exactly the way we got used to paper jams or dead pixels. But one of the coolest things about working with this stuff is getting to be there as this kind of glitch is being solved for the first time, and getting to show people something, which one day will be pretty boring, in its raw, exciting, not- quite-there-yet state.

Then one day we can look back at these glitchy first steps, shake our heads with a staggering sense of perspective, huddle closer around the warmth of our polished, boring household appliance, and tell everyone, "I remember when..."

*Extending this metaphor to, say, politics, is left as an exercise to the reader.

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