Category Archives: Personal Fabrication

Robogami: “Democratizing” Robot Building?

In a recent paper, Cynthia Sung and colleagues at MIT describe their automated design system, which addresses a “long-held goal in the robotics field has been to see our technologies enter the hands of the everyman [sic].” [1]

Well, I don’t know about that. Every nerd, maybe.

The idea is a high level design system that generates simple “fold up” robotic vehicles, suitable for fabrication with ubiquitous laser cutters and other shop tools. The computer system helps the designer create the “geometry”, the 3D shape of the vehicle, and the “gait”, how it moves. The system shows the results in a simulator, so the designer can rapidly iterate. The prototype is then sent to a printer, and snapped together with appropriate motors and wires.

One of the main challenges in robot design is the inter- dependence of the geometry and motion.


As the paper makes clear, this idea was influenced by a number of current trends which I’m sure are bouncing around MIT CSAIL and everywhere esle: computational aided iterative design, rapid prototyping with personal fabrication, and, of course, Origami <<link to post>>.

The system also reports performance metrics (e.g, speed of locomotion), and helps optimize the design.

Of course, this isn’t really a general purpose robot design system. Aside from the fact that the hard part in any design is figuring out what to design (and diving into iterative prototyping often distracts from careful thought and research), useful robots have sensors and manipulators, as well as machine learning or domain knowledge or both, which is not part of this design.

This system is really only about the body and the movement: essentially, the basic shell of the robot.  Important, but really only the foundation of a working, useful robot.

“The system enables users to explore the space of geometries and gaits”

It’s cool, but not the whole story.

And, let us not forget, the appearance and sociability of the robot is increasingly important. These cute little robogamis look like toys, and are little more use than a toy. These are certainly not social robots!

Now, if you sold this as a “toy factory”, perhaps with some stickers and funny voices, you’d have a bang up product. Don’t give Suzie a doll, give her a machine to make as many dolls as she wants!  And the dolls move and talk!

Now that would be cool!

  1. Adriana Schulz, Cynthia Sung, Andrew Spielberg, Wei Zhao, Robin Cheng, Eitan Grinspun, Daniela Rus, and Wojciech Matusik, Interactive robogami: An end-to-end system for design of robots with ground locomotion. The International Journal of Robotics Research:0278364917723465, 2017.


Robot Wednesday

Barcelona Fab Market for Open Source Design

Cat Johnson writes about the “Fab Market”, which is an initiative associated with the world-renowned Barcelona Fab Lab. The basic idea is an online shop that sells products to be made at a local Fab Lab. The designs are created by designers anywhere in the world, and are supposed to be open source. The Barcelona group curates the collection, conducting quality control and overseeing the system.

The business model appears to be that you will pay to obtain either the plans (which are supposedly “open source”), or the parts ready to assemble (DIY), or a fully assembled product. The fabrication and assembly are done at your local Fab Lab—supporting the local economy and reducing transport costs. Some of the revenue goes to the local Fab Lab, some to the workers, and some to the designer.

This effort is part of a larger vision of “Fab Cities, which imagines more self sufficient cities that fabricate a significant portion of their goods locally. Even before anything like that is achieved, this idea may be an opportunity for designers and for local workers.

Johnson summarizes the potential of the Fab Market:

Some of the benefits of the Fab Market system are:

  • Engaging and empowering people in the manufacturing process
  • Spreading the open-source ethos of sharing and collaboration
  • Reducing environmental impact of creating and transporting goods
  • Increasing transparency in the supply chain
  • Reducing the time and costs of production
  • Giving talented designers a platform for showcasing and sharing their products
  • Connecting a global community of makers

The big picture for Fab Market is to create a distributed economy based on good design and quality products that are made to last.

This effort joins existing “open source hardware” concepts, all of which are creating a global collection of artifacts for gardening, office furniture, clothing, plastic recycling and housing and homesteading.

In the same vein as Fab Market, Obrary is a global library of open source designs, available for free download (under creative commons).

Looking at Obrary back in 2014, I commented:

Suggested Feature:  One thing I would really like in a service like this would be some way to find local workers who will build. For example, if I need beehives, and I find a design I like at Obrary, and I want to buy one or more.  It would be nice to have a way to find one or more people in my town with the skills and tools, and pay them to do the build. In this case, there might reasonably be a “suggest donation” back to the designers, but most of the money would be in my local economy, supporting families where I live.

“This can be done informally, and I’m sure it will.  But is there a role for something like Obrary in this process?  And if so, how should it be done?”  (Posted September 5, 2014)

Voila! Barcelona is trying to do exactly this with their Fab Market. How can I disagree with something that was my own idea! 🙂

The obvious next step is to integrate and cross-fertilize these “open source hardware” collections. For example, it should be easy to order up anything in Obrary, and the collection in Fab Market should be accessible via Obrary. Ditto for Aker, OpenDesk, The Global Village Construction Kit, and so on.

I think this kind of interoperation should be doable, with a little bit of imagination to make Fab Market, Obrary, and so on part of an open network of catalogs. (Talk to your local librarian about open standards for catalogs….)

Such a development will also make it possible for others to join in with yet other curated collections of open source hardware, possibly with different business models. For example, garden equipment might be discounted for people who are certified participants in local food exchanges.

Note that Fab Market and the other sites are effectively offering their services as expert curators. This means that a consumer can have several options among curators, to get different perspectives. Opening up the curating process will make it possible for bottom up and peer-to-peer “curation”, so anyone can pull together an inventory of designs, and offer them to the global market of local makers.  It is also an opportunity for local makers and builders to advertise their expertise (by referring to the global catalog).

This is an interesting developments. We’ll see what happens in the future.

  1. Cat Johnson, Here’s How Fab Market is Creating a Sustainable Marketplace. Sharable.January 17 2017,


Hacking 3D Printing

I’ve written about our great age of making which has led in the emergence of community based maker spaces, and revolutions in product development and manufacturing.

One of the key technologies is additive manufacturing, most famously, inexpensive 3D printing. At the heart of 3D printing and other digital fabrication is the “executable design”, machine code files which not only describe the object, but specify how to make the object. This is one of the most exciting things about digital fabrication, because these files mean that we can do everything you can do with any digital content: publish, share (or sell) over the network, copy, and modify designs.

Unfortunately, just as you can upload, search, and download digital designs (e.g., Thingiverse), you can also hack them. This is a serious issue, especially for a business relying on digital fabrication, and for anyone building critical or dangerous machines from digitally specified parts.

The security issues are pretty simple, basically the same as for any other data, though the possible mischief is much more complicated, because the parts are physical objects in the real word. It is correspondingly difficult to detect hacking, because slight changes to any of a dozen files might create a fatal flaw that is not apparent until the parts are assembled and the machine operated.

Researchers at Ben-Gurion Univiersity of the Negev have published a very clear demonstration of this challenge [1]. The walk through a complete attack that includes hacking into the system with the design files for a quadcopter, stealing the files, monkeying with the design in ways that are not easy to see, and replacing the good file with the doctored one. The unwitting user, prints out the parts and assembles the copter—which promptly crashes when a rotor fails.

It is important to note that none of these steps is especially clever or technically deep. Hacking into the system is, unfortunately, widely known and common. Obviously, the hacker needs to know a bit about digital design to do the sabotage, but the actual method is simple as pie. Worse, the hacked file can be used as many times as wanted, so the hack might propagate quickly.

The whole point is just how straightforward and simple the attack is, and to give a very visible and memorable image of the consequences.

With the growth of additive manufacturing worldwide, we believe the ability to conduct malicious sabotage of these systems will attract the attention of many adversaries, ranging from criminal gangs to state actors, who will aim either for profit or for geopolitical power

Another point to comment on is that this particular attack didn’t even touch the control software and logic, which are equally vulnerable in many cases.  Yoiks! And don’t forget the other stuff, such as the controller, the sensors, and the data streaming software used by the copter—any and all of which could be hacked just as easily.

In addition, the BGUN hack was designed to illustrate the fact that it is very difficult for humans to visually verify these design files. The data is pretty much beyond human understanding, and the part looked OK, even though it had been modified to have a fatal flaw.

The unfortunate implication is that it is difficult to trust design data in general, even without deliberate hacking, how can you tell if this part is a good design or not? I can see a need for provenance, to try to establish a chain of trust for all the parts of your system.

  1. Sofia Belikovetsky, Mark Yampolskiy, Jinghui Toh, and Yuval Elovici, dr0wned – Cyber-Physical Attack with Additive Manufacturing. Ben Gurion Univiersity of hte Negev, 2016.


The Mighty Megaprocessor

OK, this is cool! I can’t say that I want one—but I would love to visit it to admire the shear “wondrous insanity” of this guy.

As Steven Cass puts it, a monument to our kind of crazy

Sensei James Newman, a man with time and space to burn, has built a fully functioning 16-bit “microprocessor”, blown up to macroscopic scale!

The Megaprocessor.

Motivated by curiosity, Newman built all the components, to implement a simple instruction set, registers, and memory.  The resulting beast is 10m long and 2m tall, with 40,000 transistors and even more LEDs. Evidently he also wrote an assembler and simulator, as well. Phew!

Giants walk amongst us!

The resulting processor is far less capable than the computer in a smart watch, yet consuming much more power and taking up much more space!

Newton plans to prepare some tutorial walk throughs, to explain how everything works, and how to build it from the ground up. Very cool!

One thing that is interesting is that this is project is that it is a sort of walk-in, whole body computer—unlike tiny, sealed chips, you get a really visceral grasp of how things work and what is happening.

But this is far, far from “invisible” computing, and certainly not wearable! Actually, it wears you!

And, by the way, there is no touch screen!

The Megacomputer is to appear in the Centre for Computing History at Cambridge.

  1. Stephen Cass, The megaprocessor. IEEE Spectrum, 53 (10):19-20, 2016.


Public Lab: DIY Tools For “Citizen Science”

Public Lab is an interesting clearinghouse for DIY “citizen science” tools and information. The general idea is to make available open source instruments and datasets to enable ordinary people to collect, analyze, and disseminate environmental data. I don’t know how “scientific” this might be in all cases, that depends on how you go about it. But it is certainly putting tools in the hands of the people.

“Public Lab is a community where you can learn how to investigate environmental concerns. Using inexpensive DIY techniques, we seek to change how people see the world in environmental, social, and political terms.”

Their offering includes an archive  for posting “datasets”, and a bunch of DIY instruments for collecting environmental and biological data.

The Archive

The archive is mostly maps constructed from aerial photography. The archive is curated by Public Labs, who, presumably, require some assurance about the provenance of the imagery.

To add your open source map to the archive, contact and be prepared to provide some background and to tell the story of your map.

Not much detail here about this curation process.

The archive is part of the overall political goal of Public Lab , so the datasets may have definitely political purposes. For example, one series of images records coast areas of Louisiana, showing what looks like oil slicks. <<link>> The purpose is explicit:

This photographic effort and mapping allows us to show that in great detail to a mass audience, and hold BP accountable for its damages,”

This is clearly political propaganda, and the Public Lab tools help make the images look “scientific”, which surely helps the political message.

But this is somewhat dubious science at best. I can’t find any ground truth for these images, to document that the dark spots are, indeed, oil, and from what source (unfortunately, there are a lot of things spilling oil along every coast). Worse, there is no assessment of the actual damage, much of which is not visible in these images. For that matter, without a baseline, how can we assess the damage that might be caused whatever those black splotches are?

Still, these images are dramatic evidence that suggests environmental problems that need to be investigated and handled. Not that we needed more evidence that Louisiana is a mess from the petroleum industry.

The Tools

The DIY tools are much more interesting that the archive. The tools range from the sublime to the ridiculous. There are several devices for assaying water and air quality. These are quite clever, and might be used to monitor your local environment.

On the “ridiculous” end, is a giant selfie stick, used to hoist a camera 5-10 meters overhead, to make a “map” of your garden or similar area. There is nothing wrong with this idea, it’s just kind of, well, not original.

On the more sublime side, the aerial photography is also supported by small blimp and kite systems. Now this is kind of cool, and actually enables some serious reconnaissance (not to mention snooping on neighbors). Add in toy quadcopters, and we’ve got a significant air force, for better or worse.

The various measuring instruments offer cheap ways to measure dust in the air, dirty water, chemicals such as formaldehyde, or other chemicals associated with industrial processes. While much of the documentation explains the construction of the device (usually accompanied by cost comparisons to professional labs), the most important stuff is how to use the instruments.

In particular, it is critical to sample in strategically meaningful patterns, and document the sampling very carefully. The readings mean little if we can’t match them to a time and place, and the meaning can only be constructed from looking at data from the whole area.

Many of the projects give examples of how to organize these efforts, and Public Labs is a digital community dedicated to helping people organize this kind of project. These are critically important features.

Use With Care

I’m impressed with the array of tools, and the overall open source model of Public Lab. I sympathize with their motivation, and much of the work is a good model for any local community to follow.

I remain cautious about over interpretation of environmental data, especially from sparsely deployed, low cost sensors. Most data is ambiguous and noisy, and it is easy to see what you want to find in the data.

This is particularly a challenge when it is your own home and family that may be in danger, and if you go in assuming that “they” are covering up evil doing. Going in with a determination to “show that in great detail to a mass audience, and hold BP accountable for its damages”, you are not well positioned mentally to carefully evaluate the evidence.

It is also important to think globally. These highly localized measurements may not be especially helpful in actually addressing the challenges. For example, documenting water quality issues in one locality is important, but fixing the problem must deal with the whole watershed and especially what is happening upstream.

A Missing Piece: Public Review

Conventional science uses peer review, independent replication, and general devils-advocacy to assure the quality of data and inferences. Perhaps Public Lab might consider something in the way of a review process, with “points” awarded for finding errors and alternative explanations. Anything that survives a thorough criticism will surely have more credibility.

The archive itself should record these reviews and revisions, and there should be a separate section for “five star” datasets that have gone through extensive peer review.

This process can be time consuming and expensive, especially when it drives you to go back and do some more measurements in order to fill in a hole or rule out an alternative explanation. But perhaps using something iike Loomio, it might be possible to create a light weight process that can recruit sharp eyes and minds around the globe to help validate these datasets.

By the way, this is one way that conventional science targets future resources: when a review indicates that current data raises critical unanswered questions, this motivates additional studies. Discussions at Public Labs might generate well specified calls for “most wanted” datasets.

These discussions would also be a channel for cooperation with other parties, including professional scientists who might help connect the dots and shore up the findings with additional data and theory.

A Good Place To Start

Despite my reservations, this is a very useful set of tools, and a good place to start.


Cool Idea: Acoustic Voxels

Another cool paper from SIGGRAPH, “Acoustic Voxels”.

Dingzeyu Li and colleagues at Disney and elsewhere have developed techniques for creating shapes that have specified resonant cavities to make specific sounds. These “voxels” (which really should be called something like “tootels” or something) also “snap together”, so you can construct a complex sound generators out of primitive pieces.


As they write, this principle underlies many musical instruments such as flutes or pipe organs, as well as headphones and engine mufflers. But the “the influence of the shape on the filtered frequency bands is complicated and unintuitive”, so simple cases have been used by design.

This work uses several techniques that are now cheap and ubiquitous.

a computational method that assembles basic shape primitives into a complex geometry, one that produces the desired acoustic filtering. In particular, we consider a simple type of shape primitive, a hollow cube with circular holes on some of its six faces

First, the “voxels” are standard cubes with holes, which can be parameterized easily. They precompute the acoustic properties of many possible cubes of different sizes and with different holes open and closed. These cubes can be connected, and the properties of the resulting in and out flows are easily computed.

This library of shapes gives them a space of filters that can be combined in many ways.

To design a specific filter, they use a Monte Carlo process of searching through candidate arrays, seeking optimal combinations. Each potential combination can be simulated rapidly (using the precomputed properties and connections), and rapid computation will yield one or more array to match the goal.

Finally, ubiquitous 3D printing makes it possible to fabricate the “voxels” to create any desired array. (If you had to hand carve each one, this would be rather unwieldy!)

This latter feature is critical, because it makes it possible to realize these custom filters in physical form.

Of course, the resulting “instruments” are rather simple and crude. The demo shows some custom “trumpets”, which play a handful of notes. Not even as complicated as a simple flute.

Inspired by this idea, I wonder how well this method can be extended.

For one thing, I’d like to add finger holes, like an ocarina or flute. That should be doable, though probably not without substantial changes to their computations. (I’m pretty sure that putting in an air hole will affect the whole array, not just the local voxel.)

I imagine that this approach could be combined with other simple models of resonating strings and membranes, to add other kinds of modules to the array. Again, this will require different computations. (E.g., the ‘outflow’ from a drumhead module can be a pretty complicated ‘inflow’ to the resonator array.)

OK, I admit that I really have no idea what I’m talking about here! But this project inspires me to dream about rapidly prototyping wacky new instruments.

The main thing I like about this is the tangible results. We have extremely sophisticated abilities to digitally synthesize pretty much any sound we want. Given enough computation time, we can simulate sound generation, and just plain make up sounds, combine them, and deliver them at resolutions greater than any system can detect, including the human ear.

But these “arrays” come out as hand held “instruments” or mufflers or whatever, and you blow into them or hook them to a motor or something physical. That’s the cool part.

Very neat work.

  1. Dingzeyu Li, David I. W. Levin, Wojciech Matusik, and Changxi Zheng, Acoustic voxels: computational optimization of modular acoustic filters. ACM Trans. Graph., 35 (4):1-12, 2016.


New 3D Fabrication Techniques: CofiFab

From University of Science and Technology of China and collaborators, a cool hybrid method for fabricating 3D objects, called “CofiFab, a coarse-to-fine 3D fabrication”.

Using techniques familiar from large sculptures and architecture, they use 2D laser cutting to fabricate a snap tight space filling armature to support the object, and 3D printing to fabricate patches of the outer shell, rendering the fine surface detail. The algorithms do a lot of fussy work to come up with efficient sets of parts, and to work out the jigsaw puzzle construction.

This approach uses both techniques to their best advantage. The 2D parts are quick and cheap, and the snap tight structure is light and very strong. The 3D printing using models created from surface scans can render the detail beautifully, but is slow and expensive and fundamentally pointless for filling in large volumes (why lay down layer after layer after layer of unneeded plastic deep inside an object?).

By the way, the decomposition process is useful too, because it opens the way for parallel fabrication of the multiple pieces simultaneously on multiple machines. This allows a trade off of fabrication costs (i.e., number of machines, power consumption, material wastes, etc.) against time to delivery.

As I noted, this concept has been used for millennia to decorate buildings with carved panels over structural walls. It has also been used in large metal sculptures (e.g., the Statue of Liberty).

By Islander (Pentax ME) [GFDL ( or CC-BY-SA-3.0 (, via Wikimedia Commons
The algorithms are quite clever, working out the hidden snap tight structure, and then the visible 3D pieces to attach to it. I haven’t had time to really grok this work, but it is really, really neat.

The authors note that the current technique is mainly for “concave” objects, with quite a bit of space inside (to allow the snap tight structure). I’m sure this limitation can be overcome in several ways, including decomposition of objects into multiple “concave” pieces, and other combinations of 2D and 3D fabrication.

It is interesting to think about how this technique might combine with other advances in “origami”, foldable designs. I could certainly imagine fold-out-then-snap-tight structures. I’m not sure how to attach the shell, but let’s keep thinking about it.

In any case, the pieces produced by CofiFab are certainly amenable for “flat pack” shipping and assembly.   So, this could be delivered a digital plans to be fabricated on site, or pre-made and shipped in a light, compact container.


  1. Peng Song, Bailin Deng, Ziqi Wang, Zhichao Dong, Wei Li, Chi-Wing Fu, and Ligang Liu, CofiFab: coarse-to-fine fabrication of large 3D objects. ACM Trans. Graph., 35 (4):1-11, 2016.