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Robotics Technology

Machine Prints 3D Copies Of Itself 341

TaeKwonDood writes "Automated machines have been around for decades. They have basically been dumb devices that do simple assembly tasks. But RepRap takes that a step further because, instead of assembling pre-fabricated parts, it creates 3-D objects by printing them — squirting molten plastic in layers — and then building them up as the plastic solidifies. It works on coat hooks, door handles and now it can even make working copies ... of itself. The miracle of additive fabrication, coming soon to a robotic overlord near you."
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Machine Prints 3D Copies Of Itself

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  • I... (Score:4, Funny)

    by __aardcx5948 ( 913248 ) on Thursday June 05, 2008 @07:57AM (#23666157)
    ... for one, welcomes our new self-replicating copy machine overlods.
    • Re: (Score:2, Insightful)

      by jo42 ( 227475 )
      Yeah, whatever. It might be able to 'print' itself, but it still needs a human brain and hands to assemble it and actually make it work. :-p
      • Re:I... (Score:5, Informative)

        by Gerzel ( 240421 ) <.brollyferret. .at.> on Thursday June 05, 2008 @08:37AM (#23666463) Journal
        It can't even print itself as it still requires non-printed parts.
        • Re:I... (Score:5, Interesting)

          by Sebastien_Bailard ( 1034810 ) on Thursday June 05, 2008 @08:45AM (#23666559) Homepage
          Fussing that RepRap is not 'perfectly self-replicating' yet is an extremely common criticism. This pedantic but factually true statement glosses over the fact that it's a machine that cheaply and easily makes its own parts*, using inexpensive feedstock. And it can make other useful things. That's the important stuff, which your criticism fails to address.

          *Aside from common stuff from a hardware store and an electronics store.

          (Yes, I'm a RepRap developer, and yes, that's a cut-and-paste.)

          • by Bwian_of_Nazareth ( 827437 ) on Thursday June 05, 2008 @09:06AM (#23666759) Homepage

            And it can make other useful things. That's the important stuff, which your criticism fails to address.
            Fry: Isn't that the machine that makes noses?

            Professor Farnsworth: It can do other things, why shouldn't it!
          • Re:I... (Score:5, Insightful)

            by LordLucless ( 582312 ) on Thursday June 05, 2008 @09:18AM (#23666931)
            I love the idea of the RepRap as much as the next geek. But it's been posted on Slashdot at least three times that I can recall, and the headline or summary has always claimed, as this one does also, the factually incorrect statement that the "Machine Prints 3D Copies Of Itself". It doesn't. It's cool and all, and it's getting there, but it doesn't.
          • Re:I... (Score:5, Insightful)

            by Anonymous Coward on Thursday June 05, 2008 @09:25AM (#23667021)
            Perhaps this criticism is extremely common because someone keeps claiming that RepRap is self replicating, when in fact it is not?
          • Re:I... (Score:5, Insightful)

            by Anonymous Coward on Thursday June 05, 2008 @10:23AM (#23667829)
            First, I love the idea of the RepRap and am seriously thinking of building one.

            But really, claiming self-replication here is only slightly less laughable than someone claiming their inkjet printer is "self-replicating" because it can print the manual that comes in the box.

            What we need is *quantification* - numbers. For example, choose one of the following measures:
            * part count
            * part cost
            * part mass
            * part compexity (harder to measure, but this is what really counts)

            and then find the value of X in this statement:

            "RepRap is X% self-replicating by [measure]"

            My guess is that even by the most favorable measure (probably mass), the number is well under 50%, and by other measures it's under 10%.

            But progress will be made, the value of X will increase, and that's what matters. Publicizing new values of X will attract attention and pique interest. Making unquantified claims of "self-replication" mostly just invites the fussing you're complaining about.
          • Re: (Score:3, Interesting)

            by fugue ( 4373 )
            If it can really print itself, the cost of replication goes down to the cost of parts. This is starting to sound a lot like the GPL's provision of distribution for the cost of media. Are we about to see GPLed hardware?
          • Re:I... (Score:5, Insightful)

            by thePowerOfGrayskull ( 905905 ) <> on Thursday June 05, 2008 @11:43AM (#23668983) Homepage Journal
            "The amazing thing about a dancing bear is not how well it dances, but that it dances at all. "
        • Re:I... (Score:5, Informative)

          by Anonymous Coward on Thursday June 05, 2008 @09:01AM (#23666713)
          What it does is print the plastic parts needed to make a copy of itself - you still need steel rods, motors, nuts and bolts, nichrome wire to make the heater core and a handful of small Anduino circuit boards. And of course you have to bolt it together yourself. Pretty soon it should be able to make its own circuit boards - but you'll still need to add electronic components.

          It's a significant step - but the slashdot blurb wildly over-sells it.
        • Re:I... (Score:5, Funny)

          by Fuzzums ( 250400 ) on Thursday June 05, 2008 @09:24AM (#23667007) Homepage
          Maybe it can print an order form for those parts?
      • least, until a human makes it print a version of itself that automatically makes copies of itself. Interesting experiment, what could go wrong?
      • Let's be honest about the self-replicating capacity of RepRap. If this device were even close to being able to produce the electronics embodied in itself, it would have to be much more complex than just a manufacturer of 3-D plastic parts. Without those electronics, the device is really just a skeleton.

        I submit that without the capacity to manufacture a working integrated circuit, the claim that the device can replicate itself should be considered a deliberate act of fraud.


    • by njcoder ( 657816 )

      ... for one, welcomes our new self-replicating copy machine overlods.
      Just remember, if you can't outsmart them, get the stupid people to defeat them.
    • Re:I... (Score:5, Funny)

      by bestiarosa ( 938309 ) < agent59550406 @ ... r p t> on Thursday June 05, 2008 @09:01AM (#23666711)
      You comment to this dupe article is is a dupe of my comment in the original article: []

      I for one welcome our new self-replicating Slashdot article overlords!
  • by winterphoenix ( 1246434 ) on Thursday June 05, 2008 @07:58AM (#23666165)
    While I appreciate the commercial benefit of this technology, the geek in me is a little more interested in the advancement toward the robot invasion. And by "interested" I meant "excited."
  • Dupe! (Score:5, Informative)

    by RMH101 ( 636144 ) on Thursday June 05, 2008 @08:02AM (#23666187)
    Haven't I heard this before?
  • Sweet (Score:5, Insightful)

    by Ninja_Popsicle ( 1029246 ) on Thursday June 05, 2008 @08:03AM (#23666197)
    This is take piracy to a whole new level. What fun.
    • Re:Sweet (Score:5, Insightful)

      by NoobixCube ( 1133473 ) on Thursday June 05, 2008 @08:11AM (#23666269) Journal
      Can't wait to print off some Gundam models from 3d model files, instead of shelling out for the expensive model kits :P.
      • Re:Sweet (Score:5, Informative)

        by OeLeWaPpErKe ( 412765 ) on Thursday June 05, 2008 @09:22AM (#23666983) Homepage
        Won't work with this machine unfortunately ... it lacks a support material, so it can only print a certain, very limited class of 3d shapes.

        In fact it can't print any structures that won't retain their shapes when melted to, say 5 degrees below their melting point.

        The safe class of objects that it can print are those that are basically straight-up walls upon a flat base. The most complex stuff it would be able to print is a gothic castle (the ones with tiny windows), and you'd have to put the roofs on top of them afterwards.

        The "full" class of objects it can print are those where a finite element stress analysis (*with* gravity active obviously) doesn't have any red spots.

        (and now translation from technobabble to bad news :)

        It can't print Gundam models. At least not directly. For a less limited class of objects you could make 2 half-negatives, allowing you to mass-produce them. You'd have to paint them afterwards.
        • Re: (Score:3, Informative)

          by nicklott ( 533496 )
          I neither know what a Gundam is nor know how this machine works, but on the reprap site it says:

          There are two heads to allow a filler material to be laid down as well as the plastic. This filler is used to support overhanging parts of the objects being built, and is removed when the process is finished
          Which leads me to believe that it can in fact make Gundam models.
  • Close but... (Score:5, Informative)

    by Smidge204 ( 605297 ) on Thursday June 05, 2008 @08:03AM (#23666201) Journal
    ...not quite there yet.

    FTA (emphasis mine):

    The materials, plus the minority of parts that the machine cannot print, cost about £300.
    It also does not actually assemble the parts it creates. So close and yet so far.
    • Re:Close but... (Score:5, Informative)

      by NightWhistler ( 542034 ) <alex.nightwhistler@net> on Thursday June 05, 2008 @08:16AM (#23666307) Homepage
      From the pictures in the article it seems to mostly consist of small metal pipes, with pieces of plastic connecting them.... from what I gather it's only able to print the plastic connection parts, so I'm not sure how this counts as "self-replicating".

      Also it has a big bunch of wires coming out the back, which I bet are not replicated either... so someone was jumping the gun a bit while writing this article :)

      Still... this is some seriously cool technology... if the resulting plastic parts are strong / durable enough it could certainly have a huge impact... essentially being able to download physical objects from the internet...
      • by Joebert ( 946227 )
        I think it's about time I volunteer in my community & start collecting the contents of the plastic recycling bins in front of everyones houses on trash day !
      • from what I gather it's only able to print the plastic connection parts, so I'm not sure how this counts as "self-replicating"

        It doesn't. I'd say you can call something self-replicating if it can reproduce itself using only the essential raw materials. In this case: plastics, metal(s), energy. Perhaps a lot more ingredients, but at least those.

        A good comparison is reproducing an OS in a Linux-From-Scratch style (using only source code, disk space and CPU cycles). *THE* thing you need is a C compiler. But to run that, you need a kernel, and a C library below. Then you need shell scripts to automate it, thus a shell. Most source

      • Re:Close but... (Score:4, Interesting)

        by smaddox ( 928261 ) on Thursday June 05, 2008 @09:35AM (#23667171)
        The picture makes the child device look like a cheap piece of crap. But, i guess if it works, who cares.

        I would galdly pay $300 to build on of these if it could build new plastic caps for the back of remote controls.

        There are so many little pieces of plastic that break and make a product useless. If I could replace them after an hours work, I would be sooooo happy.
    • At the top, it says "RepRap makes its first complete working replicated copy!"

      But below, it says: "You could make lots of useful stuff, but interestingly you could also make most of the parts to make another 3D printer. That would be a machine that could copy itself."

      (Emphasis added)
    • by ahecht ( 567934 )
      Maybe it's a minority in terms of numbers, but from looking at the pictures a majority of the mass of this part was not printed. Basically the machine is made up of metal rods, motors, and wires all held together with plastic brackets and metal screws. All the machine made was the plastic brackets.
    • Whether a machine is considered self-reproducing or not is somewhat subject to interpretation I suppose. Similar issues arise with quines [] (self-reproducing programs). For example, consider the classic C quine,


      For me, this is not a true quine, because there is no "#include<stdio.h>". It will not compile on typical C compilers. (There are longer quines that do have the include.)

      Basically, you have to agree on a

  • by elguillelmo ( 1242866 ) on Thursday June 05, 2008 @08:06AM (#23666227)
    I have some old Natalie Portman's pics to print out!
  • by stoofa ( 524247 ) on Thursday June 05, 2008 @08:07AM (#23666233)
    Won't everyone just buy one, make it clone itself and then send it back for a full refund?
    • by lilomar ( 1072448 ) <> on Thursday June 05, 2008 @08:21AM (#23666343) Homepage
      The guys who designed this thing aren't a business. They put the design online and the list of parts online for free, and tell anyone who wants to make one for themselves, then print one off for a friend, who can make one for his friend....
    • Re: (Score:3, Interesting)

      You joke, but in the woodworking industry companies make enormously sophisticated jigs for production of wooden forms with repeating features, and at least one company has sold their jigs with EULA language specifically prohibiting using it to duplicate itself or make other jigs that allow its functionality to be duplicated, AND prohibit resale of the jig. Completely bogus, obviously, but they've gone after people with civil suits for violating the EULA and gotten settlements, I've heard.
      So, yeah, people a
  • God I want one.. (Score:3, Informative)

    by CFBMoo1 ( 157453 ) on Thursday June 05, 2008 @08:08AM (#23666247) Homepage
    All the times I've owned something and one annoying plastic part breaks ruining the product. With this baby it'd be so easy for companies to send replacement parts at a fraction of the cost I bet.

    If I still had my old Dell laptop I'd print the latch that broke off a few years ago.
  • and stories about itself on /. Didn't we have an article/discussion a few days ago, and figured out the only thing this 'self-replicating printer machine' does is make copies of its case?
  • Ahh, but... (Score:5, Insightful)

    by Doug Neal ( 195160 ) on Thursday June 05, 2008 @08:14AM (#23666295)
    Can it sniff out nearby objects/people, ingest them, shred/melt them down to create new raw materials for buildling copies of itself? Thought not. We're safe... for now...
  • by tyler.willard ( 944724 ) on Thursday June 05, 2008 @08:20AM (#23666327)
    'Recently, Chris DiBona, Open Source Programs Manage at Google Inc, encouraged people to: "Think of RepRap as a China on your desktop."'
  • I am assuming that they used another method to make the very first one or else philosophers are going to rake it in for years over where the first one came from.
    • Re: (Score:2, Funny)

      by maxume ( 22995 )
      It all started when some guy rubbed some sticks together or carried away some of the remains of a lightning fire. Later, someone found some metal. Much later, organic chemistry was born.
    • Re: (Score:2, Funny)

      by Welshalian ( 733176 ) *

      I am assuming that they used another method to make the very first one or else philosophers are going to rake it in for years over where the first one came from.
      You're very clever, young man, very clever, but it's self-replicating machines all the way down!
    • by slim ( 1652 )
      The first RepRap was built from a RepStrap.

      It's a bit like bootstrapping a compiler.
  • by totallydude ( 1115447 ) on Thursday June 05, 2008 @08:23AM (#23666365)
    Lord Vader our troops are almost ready but I gotta run to staples to get some more of that plastic injection stuff for the printer.
  • It works on coat hooks, door handles and now it can even make working copies ... of itself.

    I didn't even have to read TFA to know this ain't true...

    Unless the machine can also make it's own electrical components...Gears and even parts of pumps I can believe, but without some way to move those electrons around, it ain't happenin'.

    • Re: (Score:3, Insightful)

      by smaddox ( 928261 )
      Cutting a metal cylinder is easy with a saw. Gluing into the plastic housing is easy with a clamp. Wrapping wire for a engine is easy, as is buying one online for a few bucks.

      The point is we have an easy way to make plastic parts that otherwise would have to be special ordered. This would complete any garage as a prototype fab. It would be amazing for lab work in which I always want a piece of plastic of a certain shape, but end up having to wait a week to get it made out of much more expensive metal in the
  • you haven't thought your cunning plan all the way through

    you forgot the part about who plugs you into the wall

    who's in control now biatches!
  • by skware ( 78429 ) on Thursday June 05, 2008 @08:32AM (#23666413) Homepage

    Copy this story.

    (originally published in Nature Magazine, January 2006)

    Cory Doctorow

    The coppers smashed my father's printer when I was eight. I remember the hot, cling-film-in-a-microwave smell of it, and Da's look of ferocious concentration as he filled it with fresh goop, and the warm, fresh-baked feel of the objects that came out of it.

    The coppers came through the door with truncheons swinging, one of them reciting the terms of the warrant through a bullhorn. One of Da's customers had shopped him. The ipolice paid in high-grade pharmaceuticals -- performance enhancers, memory supplements, metabolic boosters. The kind of things that cost a fortune over the counter; the kind of things you could print at home, if you didn't mind the risk of having your kitchen filled with a sudden crush of big, beefy bodies, hard truncheons whistling through the air, smashing anyone and anything that got in the way.

    They destroyed grandma's trunk, the one she'd brought from the old country. They smashed our little refrigerator and the purifier unit over the window. My tweetybird escaped death by hiding in a corner of his cage as a big, booted foot crushed most of it into a sad tangle of printer-wire.

    Da. What they did to him. When he was done, he looked like he'd been brawling with an entire rugby side. They brought him out the door and let the newsies get a good look at him as they tossed him in the car. All the while a spokesman told the world that my Da's organized-crime bootlegging operation had been responsible for at least 20 million in contraband, and that my Da, the desperate villain, had resisted arrest.

    I saw it all from my phone, in the remains of the sitting room, watching it on the screen and wondering how, just how anyone could look at our little flat and our terrible, manky estate and mistake it for the home of an organized crime kingpin. They took the printer away, of course, and displayed it like a trophy for the newsies. Its little shrine in the kitchenette seemed horribly empty. When I roused myself and picked up the flat and rescued my poor peeping tweetybird, I put a blender there. It was made out of printed parts, so it would only last a month before I'd need to print new bearings and other moving parts. Back then, I could take apart and reassemble anything that could be printed.

    By the time I turned 18, they were ready to let Da out of prison. I'd visited him three times -- on my tenth birthday, on his fiftieth, and when Ma died. It had been two years since I'd last seen him and he was in bad shape. A prison fight had left him with a limp, and he looked over his shoulder so often it was like he had a tic. I was embarrassed when the minicab dropped us off in front of the estate, and tried to keep my distance from this ruined, limping skeleton as we went inside and up the stairs.

    "Lanie," he said, as he sat me down. "You're a smart girl, I know that. You wouldn't know where your old Da could get a printer and some goop?"

    I squeezed my hands into fists so tight my fingernails cut into my palms. I closed my eyes. "You've been in prison for ten years, Da. Ten. Years. You're going to risk another ten years to print out more blenders and pharma, more laptops and designer hats?"

    He grinned. "I'm not stupid, Lanie. I've learned my lesson. There's no hat or laptop that's worth going to jail for. I'm not going to print none of that rubbish, never again." He had a cup of tea, and he drank it now like it was whisky, a sip and then a long, satisfied exhalation. He closed his eyes and leaned back in his chair.

    "Come here, Lanie, let me whisper in your ear. Let me tell you the thing that I decided while I spent ten years in lockup. Come here and listen to your stupid Da."

    I felt a guilty pang about ticking him off. He was off his rocker, that much was clear. God knew what he went through in prison. "What, Da?" I said, leaning in close.

    "Lanie, I'm going to print more printers. Lots more printers. One for everyone
  • by Detritus ( 11846 ) on Thursday June 05, 2008 @08:34AM (#23666429) Homepage
    Now all it needs is an attachment that converts organic matter into chemical feed stock and some wheels.

    "Knock, knock"
    "Who's there?"
    "You're not a self-replicating cybernetic organism?"
    "No, ma'am"

  • It makes copies of the parts needed to make a copy of itself. That's like saying a screw-making machine is making copies of itself because it also contains screws. If it "made a copy of itself", then out of the output area would appear a machine similarly capable of producing a copy of itself. Those are two totally different things!
  • Star Trek Replicator (Score:4, Interesting)

    by sm62704 ( 957197 ) on Thursday June 05, 2008 @08:46AM (#23666561) Journal
    The self-printing machine is another step to Star Trek's "matter replicator". Society will have some sweeping changes when physical property is as easy and cheap (or beer-free) as intellectual "property" (imaginary property) is to replicate.

    Someone in an RIAA/MPAA thread said that since physical property was getting cheaper and cheaper to manufacture and took less and less people to make that we need to stake our future to IP. I say this is hogwash - I may be creative, but most people aren't.The record labels are already quaint anachronisms, and the movie studios will soon follow as the cost and necessary technical expertise drop. It no longer takes lots of gruntwork to make an album; the band and a guy running the studio is all you need now. What will those who have no creativity do for a living?

    Heaven on earth is on its way and technology is bringing it here. And the greedy rich are fighting its arrival tooth and nail. Their sense of entitlement and feelings that they are better than the rest of us is sickening.
    • The self-printing machine is another step to Star Trek's "matter replicator". Society will have some sweeping changes when physical property is as easy and cheap (or beer-free) as intellectual "property" (imaginary property) is to replicate.
      Sure, if you like to to eat plastic...
    • Someone in an RIAA/MPAA thread said that since physical property was getting cheaper and cheaper to manufacture and took less and less people to make that we need to stake our future to IP. I say this is hogwash

      I'd say it's worse than hogwash.

      The argument is basically "physical property is getting cheaper and cheaper to manufacture, making it a difficult field to compete in... so let's compete in a field where the manufacturing/duplication is even cheaper (almost zero, actually).

      It will be quite interesting to see how economy and law change as manufacturing prices drop further, or if "object printers" become commonplace. The same silly arguments that are currently used to restrict duplication of information

    • the movie studios will soon follow as the cost and necessary technical expertise drop.
      Really now? That's funny, because, while indie music is viable nowadays, every indie movie I've ever seen looked like shit. We're a long way off from having Hollywood die, if it ever happens.
  • Looks like a fun toy, what does it actually cost to make anything with it though? Would it be cheaper to buy a coat hook from Wal-Mart or to print my own?
  • So a MACHINE can self replicate now! This is an achievement of a sort that most /.ters can't boast about ;) It's not fair. There must be a limitation built into this machine that would force it to seek out another machine like itself, only a different color and use half of that machine's blue-print to replicate. Then the other machine must be programmed to refuse most of such attempts without giving a logical reason for it (what's logical about not wanting to replicate as much as possible if you are
    • then the robot porn will hit it off... show me that circuit, SHOW ME THAT CIRCUIT!

      Mmmmmmmmmmmmmmmmmmmm... bad printer ;)
  • The Replicator Industry Association of America cautions that all replicators are required, prior to creating the first device, to first replicate a EULA. By buying a replicator you are deemed to have agreed in advance to this EULA.

    The EULA, rather like the United States Constitution, is a "living document" constructed of active replicator parts. It periodically downloads updates and constantly improves itself to keep up with modern jet-age progress, and the latest court decisions.

    The RIAA suggests you keep
  • make a velociraptor skull? Oh yeah, that was Jurassic Park 3. In 2001.
    • by bsDaemon ( 87307 )
      that was the sound chamber in the nasal cavity... and that was a commercial device. The point of these things is that hobbyists can build them at home and use them to build other things. Now that computers have become so comodified and commercial, we need something new and exciting to play with.
  • by tobiasly ( 524456 ) on Thursday June 05, 2008 @09:24AM (#23667003) Homepage
    Hmm, I thought the singularity would be more impressive than this. I bet Singularity 2.0 will be awesome.
  • When it makes it's own plastic cartridges too.
  • So this machine is open-source and can self-replicate?

    So when do I get one?

    I think I read it only takes a couple of hours? If the machine does that, the next day you have two, the next 4, the next 8,16,24,48... within a year everybody in the world could own such a machine, pretty cheap!

    So if I know somebody who has this machine, I can easily get a copy now? That is so cool, saves me a lot of tinkering hehe!

    Then nobody in the world will need to buy coat hooks and doornobs, we just fab it!
  • Video of RepRap (Score:2, Informative)

    by OtherFarm ( 1010907 )
    A video of Adrian Bowyer's RepRap can be found at ofpblog [].
  • by mark-t ( 151149 ) <markt@nerdflat.cCHICAGOom minus city> on Thursday June 05, 2008 @11:06AM (#23668383) Journal
    Okay... get some perspective here. The materials alone cost £400... which, giving that number a bit more meaning, works out to something over $750 USD. That's not exactly pocket change for a good percentage of people... and they somehow figure that people will just be willing to casually give them away? Sure, it's not out of reach of the average person's budget for the person who wants one, but it still strikes me as being well beyond the typical person's threshold of disposability.
  • by Animats ( 122034 ) on Thursday June 05, 2008 @11:26AM (#23668677) Homepage

    It doesn't make a "copy of itself". It doesn't make the plastic output device. It doesn't make the servomotors, the cables, the metal rods, or the control computer. All it actually makes, in fact, are the brackets used to assemble the other parts. The easy parts.

    A manual Bridgeport milling machine, on the other hand, used to be considered "self-replicating". If you have a milling machine, a small foundry, a supply of good quality steel scrap, sand, and fuel, and a skilled machinist, you can eventually make another milling machine and all the foundry equipment. Factories that made Bridgeport milling machines (the design was widely copied) did in fact make them using Bridgeport milling machines. A good 1930s machine shop really can replicate itself with only a supply of good people and raw materials.

    This machine is more hype than substance. It's just a mediocre stereolithography machine. If you want to use a good one, and you're in Silicon Valley, sign up with TechShop in Menlo Park. They have one, and it's not used much.

    • by smellsofbikes ( 890263 ) on Thursday June 05, 2008 @12:40PM (#23669861) Journal
      You bring up an interesting point. Lathes and mills, like compilers, can be self-replicating. In a belt-driven machine shop, working with somewhat crude tolerances, you can make a whole new belt-driven machine shop to the same (or maybe even slightly better) tolerances. But a '30's machine shop couldn't make modern vacuum-degassed, oil-impregnated bronze bearing stock, for instance: they could only make machines that had basically the same materials they themselves were made of.
      Our ability to work with bulk materials has always lagged somewhat behind our ability to make specific, custom materials, in other words -- consider what I think is the highest point of materials science, directional solidification casting of turbine blades, where we have figured out how to control not only what goes in, but how the molecules structurally relate to one another in three dimensions. To build a universal 3D printer, we have to learn how to print more than just atom-by-atom: we actually have to figure out how to distort atom-by-atom printing to establish strain within materials -- and that's just to replicate things we're already building.
      Anyone interested in further reading on 3d printers could stand to start by reading Saul Griffith's master thesis (pdf) [] on the subject. I'm building a larger version of the LEGO chocolate printer he discusses/documents in there, and I've gotten a couple of jobs by explaining to crabby old machinists how I managed to cut a new, true lathe spindle on my old lathe with a bent headstock spindle. The idea of self-healing and self-replicating machines has always fascinated me.

I've noticed several design suggestions in your code.