FlatPackRepStrap: Anybody pursuing it?

Greetings all,

The description of this group mentions "FlatPackRepStraps," but I haven't seen any activity specifically using this name. (Have I missed some threads on this?) The overall concept of making (the great majority of the) parts flat would certainly facilitate shipment of kits. Forrest's work has convinced me that using slabs of material (wood or otherwise) is a better way to make a rigid machine framework than the "stick-based" Darwin and Mendel designs. Since I'd like to make a machine that can do both additive and subtractive machining, increased frame rigidity is highly desirable.

I'm in the middle of a major house remodelling project, and Ikea cabinets feature prominently in that, so their virtues/shortcomings are much on my mind.
I was thinking that such a design variant might be called an "IkeaBot." However, that would probably run into legal issues, particularly if it went commercial. I thought of another name that (a) avoids this legal issue, and (b) hints at a Swedish connection and (c) follows the reprap naming convention honoring biologists:
I propose we call any such design Linnaeus after Carl Linnaeus, the father of Taxonomy; see [www.ucmp.berkeley.edu]

As (yet another part of) my remodelling, I have purchased a *huge* amount of used plywood, and -- once the basement floor is either done, or has its share of plywood set aside -- I hope to try a variation of Forrest's approach to making a more rigid structure for a repStrap. For added rigidity, I may use a sandwich construction, layering thin sheet metal on the faces of plywood for increased rigidity.

Thoughts, comments?

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Larry Pfeffer,

My blog about building repstrap Cerberus:
[repstrap-cerberus.blogspot.com]

Tim Schmidt and I are doing up some of the pieces for Eiffel and
[reprap.org]
here:
reprap.org/wiki/RBS

Dunno about sheet metal and plywood sandwiches; a good solid plywood box shouldn't need sheet metal.

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-Sebastien, RepRap.org library gnome.

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Remember, you're all RepRap developers (once you've joined the super-secret developer mailing list), and the wiki, RepRap.org, [reprap.org] is for everyone and everything!

Sure; my repstrap is made out of fairly simple shaped pieces of 5mm ply-wood, with some bits of spare MDF I had lying around; I'd be happy to knock up some template / drawings for you but it'll be a week or two before I have time.

Michael,

Thanks for the offer. I'm always appreciative of drawings, esp. with dimensions. However, since I'm still mored in my kitchen remodelling project, don't do this -- any faster/better than you normally would -- on my account.

I expect to start generating plywood scrap pretty soon, and I'll see what I can put together with that material. (I stil like the idea of making sheet-metal/plywood sandwich construction, but I usually favor overbuilding....)

Thanks,

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Larry Pfeffer,

My blog about building repstrap Cerberus:
[repstrap-cerberus.blogspot.com]

I live in a semi-tropical climate (we have a "rainy season" rather than "winter" with snow, etc) and have noticed a definite problem with things built out of wood. The problem is swelling/shrinking as our average humidity annually increases and decreases. (for example, our back door is either loose and drafty in the dry season, or so tight we have to kick at the bottom to get it closed in the rainy season).

So, at a guess, most of these wooden frameworks and wooden robots probably have slightly different geometry depending on the average humidity over the preceding few weeks. If I were considering a sandwich construction in wood, it wouldn't really be for strength; it would be to enhance dimensional stability by sealing out moisture. So instead of facing the parts in sheet metal, I'd be finishing them with an epoxy layer, or possibly wrapping them in fiberglass. Then again, your climate may not make this necessary or even useful.

Bear

Bear, wouldn't sealing and painting the plywood parts help negate this problem a bit? It might work just well enough to make the the fibreglass composite route a bit OTT, especially as I'd be guessing it wouldn't be as exposed to the elements as your back door

Yes, sealing and painting helps. Without it the wood actually rots. But even with normal sealing and painting, wood still swells somewhat in the rainy season. An ordinary sealing and coat of paint makes the swelling and shrinking happen more slowly, over the course of weeks or months rather than over the course of days. But you have to go to something like epoxy or marine varnish to actually make it stop. I mentioned fiberglass because wood coated with fiberglass is very very durable in addition to dimensionally stable.

Okay, I now have a mechanical design for a flatpack friendly reprap. It's a bit cool because "flat" is its normal position when Z=0, and if you want to fit it into a box only a few centimeters thick all you need do is detach the extruder. I'm calling the design the either the "Saturn" reprap, or the "Whirly", for reasons that will become apparent when you see the render.

I suppose it's as good as anything to practice some new-to-me modeling software on, so I'll try to make a rendering of it sometime between today and the end of next weekend.

Well, the "Saturn" has mechanical problems, so here's something else that could be flatpack friendly. I've decided not to build this, but it's mechanically interesting because it uses only 2 steppers to (inefficiently) control 3-axis XYZ motion. Also, the build platform and toolhead are supported with no fixed points of contact via an interesting system of gears. I call this one the Whirly-Twirly. Consider it fodder for other inventors to get ideas from.

[www.dillingers.com]

Well, I thought it was a neat design. I mean, come on. 3-axis control with only 4 moving parts? How much cooler than that can you get?

Actually, I may build one of these in a small size, as a desktop toy. For a 10x10x10 centimeter build volume, it would only need to be about 15 cm high and wide. I guess the limit is how small can I build the extruder itself.