Open Source Cardboard Robot

Humanoido

What is the interest in this? a cardboard robot project - one that walks using cardboard legs and body. I did some experiments a while back and determined the more rigid cardboard found in bulk vitamin boxes and promotions will take a servo with either no or minimal reinforcement. I have the design, just need the time to complete it. It would be cool to release open source plans for a robot like this. The idea is to update the plans from time to time. The released software could be printed with the plans for updating too and pdf distributed.

humanoido

Zoot

Here's a nice design that would work in thick cardboard (corrugated, perhaps) or better yet, foamcore.

www.instructables.com/id/simpleWalker-4-legged-2-servo-walking-robot/

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Humanoido

Zoot: great idea. The smaller robots are ideally suited for this material. Longer beams can use orthogonal supports for strength, either folded or glued in. BTW, where is the foamcore sold? Home Depot?

humanoido

Phil Pilgrim (PhiPi)

Humanoido, foamcore is sold by sign shops and art supply stores. Also worth considering is a fiber product called construction board, also sold by art supply stores. It's a very thick, sturdy, non-corrugated cardboard. It does not crease very neatly for folding, however, so the interlocking slot method of construction would probably work best.

Zoot, that walker is exactly the kind I've had in mind for a cardboard robot project. I built a similar one for the MoBoStamp-pe from G10 fiberglass sheet material, but I think the right cardboard would make a very nice construction material, too. Those robots can climb over things that get in their way. Their major shortcoming is lack of traction on a smooth surface.

-Phil

Zoot

PhiPi -- I remember the MoBug (I think that's what it was called) -- you had a video of it clambering up some books. Wasn't that laser cut sheet?

Cardboard/foamcore/sintra seems like a nice alternative, and would be inexpensive and easy to reconstruct in the case of catostrophes. Also I like it because with templates it's something that could be assembled with nothing more than X-acto knives and glue, and in a short time. And of course, it would be easy to experiment with various feet/toes for good traction, etc.

Construction board is nice as well.... I like it. In fact one trick for constructing model railroad building is take photos for texture, doors, windows, print them out on an inkjet, glue the sheets to construction board and then cut and assemble. Foamcore/board 'bots would be open to similar radically cool aesthetic customization.

(e.g. -- http://www.scalescenes.com/ which also has some nice tips for construction with heavy card stock in 1mm-2mm thicknesses)

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Post Edited (Zoot) : 7/24/2010 5:12:01 PM GMT

Phil Pilgrim (PhiPi)

Zoot,

The parts for the MoBug were cut on my CNC mill. I didn't have the laser cutter at that time. If I were to do it again, I'd probably use plywood, construction baord, acrylic, or acetal (Delrin) instead of G10, so I could cut it with the laser. It's so much easier to set up than the CNC and cuts more quickly with no mess to clean up afterwards. (G10 can be laser-cut, too, but it leaves a nasty ash on the cut lines.) One really nice aspect of the laser is that you can also cut the servo splines, so you don't have to rely on the horns that come with the servo.

BTW, to anyone contemplating cutting Sintra with a laser: don't. It contains PVC which, when vaporized by the laser, releases chlorine gas. That will not only make you sick but also destroy the laser cutter via extreme corrosion. I'm not sure about foam-core. I would assume it also contains PVC until proven otherwise.

-Phil

Zoot

I think if the idea is to provide templates, a la the example, then it would be up to the user to choose material based on what's available and their cutting tools. In my case, sans CNC and sans laser, I would use foamcore or doubled 2mm card and would cut with an X-acto. If I had a laser I would probably use 1/8" or 1/4" craft plywood, possibly Delrin, etc.

In the super low-budget, low-tech realm, a good way of cutting thick card or foamcore is to print the templates out and use craft spray adhesive to fix the templates to the foamcore, then cut on the lines and voila. This is what gave rise to the idea of printing cool textures, or the name of the 'bot, and LED holes and the like on the template before affixing -- it becomes the skin. For a shinier more durable "finish" the templates could be printed to gloss photo paper before being affixed.

Thinking out loud, actually, if we presume slot engineering, then it would be good to put several cut lines for the slots on the template, so that a given set of cut lines could be used for different thicknesses of chosen material, without the user having to manually adjust cuts, etc. Or provide alternative templates.

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Zoot

PS. PhiPi -- did you (would you) ever post the patterns for the mo-bug? Might be a good place to start because yours looked *very* cool and had that steep angle for the back legs that seemed to give much better forward power then the example I posted.

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erco

I love the enthusiasm here, but I question the "all-cardboard" direction. Probably OK for a box chassis, but for legs, you can't beat thin plywood, or a dowel for strength. Any leg joint is critical, in length and stiffness. One cardboard or foamcore bends, it's game over. Repairs to cardboard won't be pretty.

I build a lot of stuff, I have taught classes in building stuff. I get that you're after quick construction techniques, but those usually diverge from "east-to-replace" building techniques. Build it right, build it once, and liberally use reinforcing hot melt glue or CA & baking soda. You DO know about CA & baking soda, right? Try it. You can make rock hard reinforcements or parts out of them.

It's not much more work to make the mission-critical parts out of something more durable than cardboard. It would be a shame for a bent cardboard leg to end the proper function of the robot.

My two cents.

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·"If you build it, they will come."

ratronic

erco what is CA?

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D Rat

Dave Ratcliff N6YEE

Phil Pilgrim (PhiPi)

CA = CyanoAcrylate (Super Glue)

-Phil

ratronic

Phil - whats the reaction between baking soda and super glue?

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D Rat

Dave Ratcliff N6YEE

Phil Pilgrim (PhiPi)

I'lll have to refer that one back to erco. I've never tried it.

-Phil

erco

Shoot, you mecho-Noobs are in for a real treat. Use thin CA glue to make a fillet anywhere you need, and sprinkle baking soda into the wet glue. It hardens almost instantly into an epoxy-hard fillet and gives off heat (exothermic). You can alternate layers of CA and BS and make really thick layers, or complete parts. You can glue things directly to unglueable nylon servo horns (rough 'em up with sandpaper first) by encapsulating the horn all around and getting it through the holes. MUCH stronger than hot melt glue, which is the only thing some people know how to use.

You can "rapid prototype" a small part on wax paper this way, alternating layers. A link, a cam, anything. I have seen entire mechanisms made this way.

JUST BUILD IT!

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·"If you build it, they will come."

ratronic

Thanks erco!!

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D Rat

Dave Ratcliff N6YEE

Humanoido

Durability also depends on the type of cardboard. I have a high density cardboard box that I'm saving for robot legs. It's perfect for affixing bolts and with orthogonal reinforcement it should hold up for some time to come.

Few people seem to have DIY art hobbies in China so I'll have to forgo the idea about foamcore due to lack of hobby stores, though I can get lots of nylon, silk and polyester kites..

humanoido

Phil Pilgrim (PhiPi)

erco said...
You can alternate layers of CA and BS ...

I've delivered layer upon layer of BS before, but never mixed with CA!

Thanks for the tip!

-Phil

Zoot

You should be able to get foamcore in any place that sells school supplies. It's very common for art/presentation projects in schools and the like.

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Humanoido

Zoot said...
You should be able to get foamcore in any place that sells school supplies. It's very common for art/presentation projects in schools and the like.

I'm headed to the EXPO and there should be some art supply businesses in the big city - I'll look around.

Zoot

My partner and I were discussing big cardboard/foamcore 'bots over the weekend. Here a few of the things we liked about it:

- cheap (huge bonus)
- fast/sloppy construction with common household items (knife, glue) is OK (ideal esp. for younger kids where longer focus over multiple sessions just isn't possible
- relatively big "creatures" possible without huge weight and motor requirements
- along same lines -- bigger constructs not as dangerous when they go awry
- everyone liked the idea of 'bots that would bonk into each other a lot (trust me, the kids love it when stuff crashes)
- easy to keep raiding old platforms for servos, parts

So that got us to thinking about possible scenarios. If, for example, you have a 12"-24" platform, vaguely bug- or humanoido-like, you could have some 'bot wrestling/demolition derbies -- since the platform is soft, it'll absorb impacts and the platform should still be able to hack along until it's just too crumpled to move.

So that got us thinking about some easy simple ways to let the 'bot detect that one of it's legs had crumpled to the point of being unusable. The best I've come with so far is something like taking very thin tinfoil and tacking it down as a strip along each leg with just a spot of hot glue here and there. The idea is that as the leg crumples, eventually the foil will tear enough to break a circuit.

Those of you with children -- like us -- who frequent children's science museums may have seen a really common method for introducing young children to electronics with no soldering or wire cutting or anything. The kids lay down strips of tinfoil on cardboad with glue, punch holes all the way through, and then insert wire and loop it around a few times to make circuits. They're printed-circuit-ish in a way. Simple, and lets them wire up leds and motors to big cardboard Rube Goldberg-esque constructions. Would be a nice way to put LEDs on the ends of legs and such as well (sharing circuit with the crumple detector).

I think that a bug like PhiPi's or the sample I linked to above would work up to a certain size with two servos; bigger platforms I think would need to have three or four.

Just throwing some ideas out -- I will like to try out a few experiments along these lines -- given rapid construction time and the inexpensiveness of the material, I should be able to cycle through some designs in short order. Probably won't have time to kick that down until the second week of August, unfortunately. I have two big work projects that need to be dealt with before I can get some serious time in the 'bot lab

Last thought -- my partner really likes the idea of TALL 'bots.... given how light and how tall this kind of construction could be, I think a Hobbit-sized construct would be doable

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Leon

When I worked for Xerox Research (UK) many years ago, the industrial designers in our ID/HF group used Fome-Cor for their so-called soft models used to illustrate design concepts. They were surprisingly robust, and I used them sometimes for human factors evaluations. Our technicians who made them used to glue the material using PVA adhesive. It's now made by 3A Composites:

www.graphicdisplayusa.com/prod_fome-cor_board

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Leon Heller
Amateur radio callsign: G1HSM

Post Edited (Leon) : 7/26/2010 7:45:41 PM GMT

Zoot

Oh yeah, it's great stuff. Nice too, because you can make bevel cuts, parts with built-in -- and then reinforced -- hinges, etc.

For those in the states:

www.elmers.com/products/foam-and-display-boards/foam-sheets?Page=All

Most of these are available at craft houses like Michael's. I've generally seen thicknesses from 3/16" to whopping 1/2". 3/16" or 1/4" is good for a lot of purposes and isn't too expensive (the thick stuff is more expensive, but a single sheet might yield quite a number of the small number of pieces that might require a size like that.

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Post Edited (Zoot) : 7/26/2010 7:58:27 PM GMT

Zoot

I tracked down the link to Phil's great MoBug demo video and a picture:

www.parallax.com/dl/mm/video/mobug_movie.zip

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Humanoido

Working with cardboard has important techniques to keep in mind. Cloth hinges can be light weight and durable when reinforced. Consider some of the stresses on model rocket cardboard rocket tubes. You can borrow some of that laminating and epoxy-covering technology over into robotics. Some layered cardboard has the same internal beam structure as airplane wings for strength. There are numerous ideas to incorporate into cardboard robots.

humanoido

Humanoido

Still did not find the white poster board but did find more varieties of cardboard, about everything you can imagine! I'll need to stick with the original idea of this thread as I think there's a gold mine of cardboard varieties here. [noparse]:)[/noparse]

There's a hardened gray cardboard which is very strong and would be ideal for forming humanoid legs and arms. It's thin enough to drill and bolt yet strong enough to support a good amount of weight. I have some of this material, and purchased some rolls of pure aluminum, gossamer thin, for possible light weight covering.

humanoido

Humanoido

One thing about cardboard is it's flammable and can burn. So any hot components like a voltage regulator must be shielded. A good idea is to cover the cardboard with a flame resistant material - such as common aluminum foil. While the foil can deter sparks, it will conduct heat so be careful. Another idea is to supplement the cardboard with other materials in heat sensitive areas.

Humanoido

Spiral_72

Foam core may also be called Sintra, or PVC board / panel.

Humanoido

Foam core has a similar (paper) outside surface as cardboard.

http://en.wikipedia.org/wiki/Foamcore

"Foam core or Foam board is a very strong, lightweight and easily cut material used for the mounting of photographic prints, as backing in picture framing, in 3D design, and in painting. It consists of three layers — an inner layer of polystyrene clad with outer facing of either a white claycoated paper or brown Kraft paper."

Humanoido