Project Make-A-Bot

Sunday, October 17th, 2010 @ 5:25 | Make-a-Bot, Project Build Reports

I have waited long enough.

If I trace out my history of fabrication methods, I can observe that I’ve basically gotten hooked on one new methodology or machine (one sort of begetting the other) every year since 2006. Before then, my robots were practically all hand-crafted and fabricated using only basic shop tools.

2007 and 2008, my first year in the northern wasteland MIT, was the first time I had consistent access to machine tools. Thus, many of my works from then feature alot of heavy billetwork. I really liked making things out of big bricks of aluminum or solid rounds of steel.

All that changed when I found the waterjet. As one look in my project hive will tell you, I can’t build anything without a waterjetted part any more. It’s actually kind of depressing, because I will actually wait 3 days for an opening on the machine to make something which amounts to a flat piece of metal.  Instead of, you know, manning up and just cutting it out on the bandsaw.

It was during the summer of 2009, when I was an intern at iRobot, that I got introduced to 3D printing firsthand. Before then, it was just a curiosity on Youtube and Wikipedia. But at iRobot, alot of my tasks revolved around 3D printing. You see where this is going.

What the waterjet did for me in 2D, the 3D printer can do for me in 3D. I can easily put together 3D structures out of flat pieces, but why not skip directly to the 3D? Or even better, use 3D pieces to MAKE A 4 DIMENSIONAL PART?

3d printing

Commercial 3D printers, like waterjets, are big-investment machines that are closely guarded by their purchasers. Despite falling prices as more manufacturers emerge and technologies mature, a machine that produces structural parts stills runs over $10,000 commercially. I definitely don’t have that much on me at the moment, despite a surprising number of people pitching into the tips jar (THANKS EVERYONE!!!). Plus, just buying one would be no fun.

Structural is a pretty important qualifier here. There are many processes which all fall under the “3d printing” colloqualism. There’s the classic “3D printing” powder-and-binder technology such as that commercialized by Z Corporation (MITERS represent). There’s stereolithography, which uses a liquid polymer and a laser (or strong UV light and micromirrors) to solidify tiny dots of the liquid; SL and related processes can get features down to the micrometer or smaller. And then there is laser sintering, which combines the powder of 3D printing and the laser of STL to let you make parts out of anything that melts. Which is to say, anything – including metal and ceramic. SLS/DMLS is one of the latest technologies to emerge and is therefore unthinkably expensive.

Of those technologies, really only SL and SLS produce parts that can be described as “structural”. The powder-binder method can produce any color a regular printer can, however, which makes it still favorable for product development.

Oh, I forgot one method. Fused deposition modeling / Fused filament fabrication machines extrude a little noodle of plastic and drag it around to shape parts layer by layer. It produces parts which are almost as strong as the parent plastic, doesn’t have outstanding Z-axis feature resolution, but is fast and relatively cheap. It’s also the technology which has made it to the hobbyist and amateur domain.

DIY 3d printing

The “maker scene” has been enthralled by 3D printers for some time. The concept of on-demand digital, individual fabrication is pretty much the embodiment of Makerdom. As such, there have been several attempts at making an affordable, open source 3d printer. The projects which have had the widest reach are RepRap, Fab@Home and Makerbot (which itself was a branch of RepRap). As far as I know, all attempts so far have been FDM type machines – which are conceptually the simplest, since all you literally are doing is dragging a molten plastic noodle around. There’s details involved, but it’s less complicated and cleaner than diddling with powder.

For some time, I’ve been mostly ambivalent to the DIY 3d printer world. Primarily it was due to lack of research and other projects filling my time (and the waterjet having successfully seduced me), but I was also a little put off by the design limitations imposed by the RepRap project because of the end goal of self-replication…. which I find a bit creepy anyway.

I was first introduced to the Makerbot Cupcake over this past summer because Trevor built one. By then, Makerbot Industries had already refined that design so it was more robust and streamlined. I was impressed by the build quality of the Cupcake, even when it hadn’t been fully dialed in yet. I’d almost say it was on par with the Stratasys Dimension printers I used at iRobot, and certainly stellar for the sub-$1000 cost.

Maker Faire NYC

I was completely sold, though, when I tripped down to Maker Faire NYC 2010 for kicks. 3D printing had an entire three tents full of exhibitors, so I had a firsthand comparison of all the different DIY variations, as well as commercial solutions.

CUPCAKE EVERYWHERE. THOUSANDS OF THEM. Or like 20.


Also, RepRap Mendels.

The Makerbot Cupcakes here were well-tuned and well-trained, constantly producing little giveaway trinkets for the crowd. Print quality on those was phenomenal and the parts themselves solid – it took real effort to break , even between layers (I had also previously been put of by 3D printing due to iRobot’s Dimension machine making a few parts with weak layers).

Makerbot Industries chose this occasion to introduce the Thing-o-Matic, which is a bugfix, refinement, and feature request update of the Cupcake.

my turn

That was it. I spent the entire bus ride back to Boston thinking about 3D printers and the crazy things I could do with them. I contemplated just buying a Cupcake kit (or a ToM kit when they ship), since everything would work and there’s a huge userbase to turn to if it doesn’t.

…who the hell am I kidding. A few weeks of idle time while I attended to such distractions as über-RazEr and Melon-scooter let me materialize the design in my head a little more. What I was mostly after was:

  • Easy to build. I was enamored to see T-nuts on the Cupcake. I was really not impressed by the heap of threaded rod that is Mendel. I hate threaded rod with the burning passion of ten thousand power MOSFETs. Overall, I shouldn’t have to machine anything.
  • Large build volume – I wanted to aim for 6 x 6 inches square, by maybe 8 inches tall or so. Not that I think I’ll be hitting the 4 inch cube limit of the Cupcake any time soon, but it’s nice to keep in mind.
  • Modular, in case I ever want to replace something and keep the machine’s functionality.
  • The motorized build platform.

The “Plastruder” tool head is a design which has been refined many times, and they’ve got it working reliably now. There’s many details in the extrusion process such as feed rate, temperature, and speed that have been figured out by the community. Therefore, I intend to just get the tool head and stick it on my own hardware – at least until I know what I’m doing.

Same with the electronics, and most definitely the software. We know what happened last time I built something requiring custom electronics and/or software (It’s still ALMOST THERE, I promise).

In all, it’ll be “Makerbot-RepRap-compatible” but on an indie platform.

Make-A-Bot

Without further ado, here’s the first pass at the CAD model. This model currently has no final geometries, dimensions, or methods of attaching anything to anything else except maybe exploiting the strong nuclear force.

The machine looks kind of like a Thing-o-Matic without the surrounding structure. The reason for making this machine more stand-alone is because of my modularity concerns – building a whole box structure with a machine integrated inside is less appealing to me than building a machine and then putting it in a Nice Box.

I took a page from the MakerBot design book by using the screwed axis endcaps. I’d have used shaft collars here, or drilled and tapped otherwise.

The axes are moved by steppers and timing belts, except the Z axis, which uses a leadscrew. I hadn’t yet specified the particular leadscrew yet, so that part is implicit.

The spider plate in the center is designed to mount the eventual motorized platform, but can also mount a conventional acrylic/kapton one. I wasn’t particularly impressed by the magnet-attached build plates of the Cupcake. It seemed to wobble alot, and suffer from poor alignment, but I’ll give it credit for convenience. I don’t mind giving up a bit of convenience if I’m not ending up building a motorized surface, so the attachment might be via thumbscrew or something.

The axes have a whole 6.5 inches of travel in the X and Y and currently 7 inches of travel in Z. This is, however, not accounting for the added height of a motorized platform or head height variations that might be yet to come.

As a result, this thing is kind of huge – a full 15 inches front to back, 14 side to side, and 17 top to bottom.

Oh, it’s also all aluminum. I have a few extra 1/4″ plates left over from the summer robot build, so it’s going to be metal. Total overkill for a process with almost zero tool pressure, but \m/etal. I’ll have to be careful in making sure the axes don’t have too much inertia or else the stock stepper motors will not be able to handle it (a clear excuse to put a bigger motor on it).

The name MAKE-A-BOT is just a silly derivation of a Bostonian slurring of “Makerbot”.

timeline

I’m guessing at this point this will be a late fall term project and probably extend into the January punt period called IAP. Most of the parts are stock, there’s zero machining (yet), and the structure is entirely waterjetted (however, I am not opposed to making it all acrylic, in case it will be laser-cut and have embedded LEDs).

Some random musings I had involving the design, which will not be in the first iteration (if ever at all), include

  • Full heated cabinet for the main machine. Having a heated base is good, but a heated cabinet is better because of the even thermal distribution in the plastic while the part is under print.
  • Printing bonded iron stators. This was the “killer app” which made me determined to build this in the first place – experimenting with the manufacturing of poured iron-epoxy stators for motors. With solid fill, each layer is bound to take several minutes, which is enough time for fast-set epoxy (60 second, etc.) to get structural enough to support its own weight. Mix in an absurd amount of iron powder or filings to the resin on the way and you will hopefully get a material with 60-70% the saturation of a legitimate iron core, but hey, at least you made it.
  • Maybe some day I can actually try making an SLS machine.

If you’ve lost track of how many things I’m working on right now, it’s technically just two – RazEr rEVolution and now the Make-a-Bot.

 

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    5 Responses to “Project Make-A-Bot”

    1. Josh Cole Says:

      Looks like I finally have a good excuse to start working on a 3D printer. I’ve wanted one since midsummer when I saw a few good articles on what a Cupcake could do. Looking forward to this!

    2. Jerome Demers Says:

      We have a Stratasys Dimension printer at school, a big one. We use it once for a robotics competition and we printer the entire chassis of our small robot. We also printer our own water turbine for the same competition. There is some pictures here http://jfduval.ca/en/?page_id=8&album=8 and video here http://www.youtube.com/watch?v=Z3ERyYSB9WI

      the only problem with the maker bot is that you can not make a hollow or undercut parts that well. It does not support deposit material that well. That is what I hear.

    3. the chuxxor Says:

      The current DIY printers actually don’t do support material at all. There’s some tricks people have pulled, such as printing the “support” out of ABS but at a lower temperature, etc. Kind of tacky and I’m not particularly impressed – for now, I accept the limitation of parts without undercuts.

      I think that’s one department in which the DIY printers are in need of hacking.

    4. Andrew Olson Says:

      This should be legit yo. Although I’d take a cnc router table over 3d printer.

    5. Jerome Demers Says:

      Here what I saw today
      http://www.thingiverse.com/derivative:3640

      Like you said, it use different temperature. It’s a start.