Sarrus Linkage 3d Printer

[fdavies] has been working on his own 3d printer. He is using printed parts, but unlike the RepRap he’s purposed Sarrus linkages in his design. If it works, this should remove the need for precision rods in building these types of CNC based machines. He’s also recovered DC motors and optical encoders from some inkjek printers. Given that many retailers require you to take junky inkjets home when you purchase a computer we’re betting you’ll find friends happy to part with their unused hardware. We’re impressed with the motion of the prototype seen after the break. Let’s hope this leads to the next generation of affordable 3d printers.


[Thanks Rich]

21 thoughts on “Sarrus Linkage 3d Printer

  1. It is inventive, but not very practical. I hope it actually isn’t the next gen in 3D printing.
    I’d like this self-imposed and pointless limitation that you can only use one tool to build a 3d printer to go away, and that it needs to be another 3D printer.

    I’d like to see the design based on cost, sustainability, ease of construction, performance, etc. and not on some empty and ultimately self-defeating concept of ‘self-replicating’.
    In fact ultimately, it would make a hell of a lot more sense to design a 3D printer that could be built by anyone, anywhere, WITHOUT the need for already having access to a 3D printer.

  2. @stunmonkey: Actually, printed parts are by far the cheapest thing involved in a reprap. They max out at about $10/lb for materials and power – the current design has around three pounds at full infill. The sarrus-based design probably saves around $80 in bearings and rod alone, and all parts only really have one obvious way to go together for assembling the machine. We’ve yet to see whether it can achieve the requisite positioning accuracy, but it’s not attached to mainline anyways.

    The “restriction” has more to do with a 3D printer being the cheapest machine to get and run available to produce the kind of parts it needs without needing skilled labor. Not using it, you either need a much more skilled operator to make your parts, or a much more expensive machine.

  3. @stunmonkey

    I think the idea here is that the more of the device that can be built from inexpensive plastic as opposed to imported parts, the better for someone in a third world country that lives on less than two dollars a day.

    Someday soon I expect that we’ll be able to print practical stuff out of discarded plastic bottles and other salvage.

    A surplus stepper motor cost me $10+ and that’s before shipping domesticity. In many parts of the world that’s pure unobtainium

    Rest assured that there are plenty of people building repstraps (junkstraps) out of more practical stuff. HaD have even covered one of them.

  4. @stunmonkey

    You may be interested in a series of books written by the late Dave Gingery, and continued by his son Vince. He gave complete, illustrated instructions on casting and fabricating all the major machine tools from scrap aluminium. This included the metal lathe, shaper, horizontal mill, drill press, accessories and upgrades. Additional books detailed a sheet metal slip-roller and brake, a bandsaw, and various other devices – like a banjo. Dave was pretty eclectic. His books are still carried by Lindsay Technical Books, and are a pretty good read. Lots of people have built his machines and have made improvements in the design and methods, but they are still fun & informative.

  5. @rallen

    Dave Gingery had a really good set of concepts, and a good series of books.

    Showing how to build an entire machine ship from nothing was brilliant, and it statred by making the simplest and most useful tool first – a lathe.

    A lathe is far more practical for third world countries than is a 3D printer, is easier and cheaper to produce and use, and has the side benefit of being able to produce the parts for a 3D printer, as well.

    Besides, if you can’t source the parts for even that locally, then how in the hell do you get clean power, a computer, software, computer-trained personnel, and the drive electronics as the precursor to the 3D printer?
    The structure itself is almost meaningless logistically.

    As well, a 3D printer is a great EXTENSION to a basic machine shop, not a replacement. The machine shop can work very well without a printer, but the printer is nigh-useless without a machine shop.

  6. @The Steven – I just passed “The Eagle” along to an email list fdavies is on as a suggested name “fdavies’ Sarrus linkage X-Y table” is a tiresome mouthful.

    @stunmonkey – I personally think that folks are a little mistaken in thinking that the end-use for this device is anywhere in the third world. This table, and the RepRap project in general, are ingenious hacks, plain and simple.

    However, they are focusing on something that you have already said was a good idea while dismissing the superfluous “third world” angle. 3D printing has a place in the machine shop. The Reprap project, and its spin off the Makerbot Cupcake, have turned simple rapid prototyping from something affordable by architects, geologists, and medical prostheticians, to something affordable by almost any high school – if the shop and science departments can pool a budget for it.

    Any third world use of a RepRap derived design is going to be in those developing second-tier economies that were intended to get the OLPC XO. (In fact, as a point of trivia, the arduinos used in this project were programmed from an XO.)

    Rapid Prototyping is not the be-all-end-all of industrial design, but having the ability to turn concepts into object quickly can be very useful and empowering. More than a self-replicating design, the RepRap is a CHEAP fabricator. It really already does the things you want a printer to do in terms of simpicity and cost.

  7. @ Everyone who is a RepRap fan

    There is one aspect of this project that isn’t obvious, but is just as revolutionary a hack as everything else – the motor controller.

    fdavies did not make any modifications to the standard RepRap controller software or skeinforge. Mr. Davies is using an arduino to control the DC motors and read the optoendcoders locally. The control signal being sent to that board is the standard stepper controller signals that come off the motor board as with any other RR-based printer. The control pulses come in, a step-count is made, and then the closed-loop control system moves the DC motors the correct amount. As a nice side-effect, you can take the gantry and yank it totally out of position, and it ziiiiip back into place immediately.

    As far as efficiency goes, it’s a total loss. Adding another processor to the chain to avoid having to re-do firmware is terrible. However, being able to throw your own hardware under the standard RepRap software with a hardware-based hardware abstraction layer is pretty cool. I am hoping that this project will inspire/disgust some of the folks involved in the firmware design end of things to actually move to an abstracted-hardware design that is easier to modify at the end-user level.

  8. I think the third-world aspect of this is a bit superfluous as well.

    I only mentioned it as that small group of folks who have taken the RepRap into a full-blown religious cult always use the third-world angle as a straw man to deflect any criticism, personally attack anyone who disagrees with their dogma, and avoid answering questions. You know – critics lack vision, are evil greedy exploiters who don’t care about the poor, Reprap will literally save the world, etc.
    Every other critique of the Reprap, including on here, has been met with that so far. I wanted to head it off early by pointing out that even if for some reason you thought that people without electricity or clean water needed RepRaps this design path still isn’t the best way to do it.

    Like you said, I agree that this is mainly for first-world individuals and education. If that is the case, this is still a dead design path as more efficient, cheaper, and better quality units can simply be assembled with cheaper off-the-shelf hardware commonly available in the first world.

    So in either case the avoidance of cheap commercially made parts like rails is pointless.

    The people invested heavily in justifying it’s “self-replicating” status are using circular reasoning, or are straight up just being disingenuous trying to push the third-world angle.

  9. Looks like this could be made with laser-cut 2D parts. I don’t think this arrangement is a true Sarrus Link. The Sarrus Link converts a limited circular motion to a linear motion without reference guide-ways ( A true Sarrus link would be driven by a circular arc imposed on the apex of the bending joint. But a true Sarrus link would introduce non-linear mathematical complexity to the print engine code – and if you’re not careful varying precision at different points on in the work-space. The solution here doesn’t appear to have this issue. This solution does indeed remove the need for precision linear bearings and rods. Nicely-done.

  10. I recognise those motors!

    I think they are the carriage drive motors from HP 6##, 7## or 8## inkjet printers. If you want some good but cheap DC motors, I can highly recommend getting them out of junk HP inkjet printers (I get mine from my local e-waste scrap dealer – very very cheap, and I give them back the printer to them to dispose of).

    I am using the motors at about 20V for the drive motors for a robot (Asus wifi router with USB2.0 and OpenWRT Linux installed running Python pyserial and pyduino, Arduino and USB stick connected using USB hub, Arduino running Firmata).

    As pointed out above, you also get precision bearing rods and very high precision optical encoders (linear or rotational depending on model).

  11. You can get relatively high precision linear bearing rods from things as rudimentary as scrap electrical conduit trued up on a fixture jury-rigged from scrap.
    You can forget the rod part get extremely high-precision linear bearing rails from common rolled steel plate and low-grade roller bearings.

    Or you can complicate the whole thing by requiring enough specialty computers, hardware and CNC programming skills to make much the same thing, only less robust, less accurate, less durable, less useful, more time-consuming, and more expensive.
    At least you’ll feel smarter than all those morons just using old-style hand tools to do the job though, ’cause you have ‘leet skills.

  12. I like it. This probably won’t become the mainstream RepRap, but this is a great way to expand the hacker workshop vocabulary, alongside your Gingery set of machines that you enhanced with CNC functionality from RepRap electronics. Also, if this is capable of printing the parts for a standard RepRap (I doubt it’s not), this might be a good RepStrap to keep around as a backup for when your main machine breaks something.

    Also, I like cheap.

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