RepLab: The Open Source, Replicable FabLab

Since the RepLab concept owes so much to the RepRap project, it seems natural to have a discussion about it here.

Marcin Jakubowski of Factor e Farm recently raised the topic of open-source FabLabs as part of his larger project of a full suite of sustainable open-source technologies for village scale, resilient high-tech permaculture. Erik de Bruijn replied:

"I propose that we call this effort “RepLab”. This is to emphasize the symbiotic relationship with the FabLab ‘movement’ that already has significant momentum and fabber projects including the RepRap, but also derivative and alternative projects (Makerbot, Fab@Home, CandyFab, P3P, Contraptor). I don’t see self-replication of parts as a condition on the short term, but either efficient fabrication through mass production (standardized common parts, e.g. nuts & bolts) or custom fabrication (preferably with tools available in a RepLab)."

The project goal is to produce a fairly comprehensive suite of automated, general-purpose fabricators which work in a variety of media. With enough development, the entire suite can display significant recursion, much like a RepRap does. This has the same promise of geometric growth and economic changes, but at a larger scale of object and a wider variety of materials.

The discussion is taking place at the group; the home page for the project is here. Hope you'll join us!

It sounds very interesting; I'm quite impressed with what you group has gotten up to, especially with the plasma cutter, LifeTrac, and Liberator.

I'm very interested in bootstrapping RepRap into other kinds of fabrication machines, starting with a hybrid CNC router / 3D printer and a pick=and-place PCB stuffer and oven fabrication chain. Eventually I'd like us to work our way up to a 5 foot by 10 foot (1.5m x 3m) CNC router.

This is our current working sketch:
[objects.reprap.org]
which has been kicking around in my head for about a month.

Would you like to RepRap to co-host the project on our wiki and on our forum? We've got a pretty mature hardware base and a pretty mature community. (And, to be honest, a bit of media presence, which never hurts.)

Thats interesting and its close to the direction I want to head although I'm thinking of something slightly different.

Because of its increased size I would look at designs that can be folded when not in use, or can have dual purposes. A 5' by 5' table is a bit awkward to deal with unless you have a dedicated shop.

Furthermore, I believe that focusing on non-contact machining methods could drop most of the rigidity requirements of router/lathe cnc operation.

The real problem is finding a metal deposition/cutting method that can be easily incorporated into a machine without a substantial cost. Most methods require a fair bit of infrastructure in gas handling, high voltage electricity, or material handling.

Some good candidate processes are plasma cutting, electro-chemical etching, and Induction furnaces

With regards to hosting, I think thats a fine idea.

I'd drop the foldability requirement, straight off, for the 1.0 version. Aside from a 'Murphy-bed' version cnc table, maybe. But every time we fold, we lose some squareness. You want cheap, stiff, and fabricatable. Maybe the 2.0 version can be folding, and it will look cooler, but if it means having to re-shim or re-square each time, forget it.

I just designed a folding bicycle cart for a drafting class. We made a 1/10 scale model out of card stock and stratasys-RP plastic. Our model user was a non-third-world bike user who lived in an apartment. Because in the third world, people can't afford luxuries like foldablity, most of the time, so if they need a bike cart, they'll store it in a friend's shed or so on. They'll pay for it if and only if they need it.

Are we going for apartment-dwelling geek toy, or something a subsistence-level megaslum dweller/farmer is going to use to generate wealth? Because the machine's usefulness will pay for the rent on the chunk of shed, basement, or workshop that it's in. And it would never get folded, any more than you'd fold a tablesaw in a production workshop. When the machine's not making stuff for the builder's personal needs, he/she is operating as a job shop. If it is tucked away and folded 80% of the time, we've failed.


Foldable will look cool, and get us on CNN. But we need easy to fabricate. I'm favoring modular, if we can. On the other hand, a bridgeport mill is not modular. On the other other hand, you can disassemble a modular 5'x5' CNC router table.


-----------------------------------------------

We can make beam from scrap wood, just by milling it down to 1x1, 2x2, etc. (25 x 25mm, 50 x 50 mm.)

-----------------------------------------------

Dual-use is lovely. Examples:

[www.thecooltool.com]
or [taigtools.com]
(The Taig mill shares parts with the Taig lathe design).

-----------------------------------------------

Electro-chemical etching sounds positive, although I think they need dedicated water filtering systems, canisters of some sort, and it turns out to be an expensive consumeable. Forrest Higgs was reading up on this a year ago, or you can ask on CNC zone.

I'm thinking about C02 laser, maybe, using generic laser tubes and maybe power supplies from white-box Chinese laser builders, but designing our own user-buildable positioning system and optical path. The user is trading time and dedicated support for money, so maybe not. On the other hand, if it's a good design, the user can maintain the system themself with forum kibbitzing.

Maybe. I don't know lasers, really.

-----------------------------------------------

Induction furnaces:
Cool, but I'd also try to adapt household microwaves for some tasks. There's a guy who melts bronze with them, but he didn't publish worth a damn.

Edited 1 time(s). Last edit at 12/05/2009 05:17AM by SebastienBailard.

Portability and ease of transport are a serious consideration. You can't cheaply ship or source parts for a machine that weighs more than you do and thats why I want to do a design that moves away from where most cnc machines are right now. Thats also why I'm going to push for non-contact machining methods, because they reduce the need for dampening machine chatter.

Also, consider that no matter what cutting method you use, it will be a pain to work with. If you have a creative way to use the magnetron out of a microwave, that would be interesting, but realize that there are several issues with shielding, and other issues.

The bronze melting is done by impregnating a crucible with magnetite and carbon powder which absorbers microwave radiation and converts it into heat. Its a neat process but is much too bulky and doesn't have a good machining process from feed stock to finished product that can be automated.


Forget wood as a building material. Its too soft and trying to pretend to achieve sensible tolerances is a joke.

Also, I'm already on version two. I have a design that looks a lot like what you have here.

What I want in the next version is to maximize how much the machine can replicate itself. For example, I want it to be able at the very least to make screws, and threaded rod. I also suspect that RepRap will be instrumental in providing plastic pieces that would be difficult to build by hand.

Ideally I want a fusion of additive and subtractive processes, and the ability to work with metals in a meaningful way on a low energy budget.

I realize that at the moment we are talking at cross purposes here, but I'm coming from already building a cnc plasma cutting table and wanting to improve on the concept.

Different processes are optimized for different materials. A cabinetmaker, a machinist, a bronze sculptor, and a robotics geek have different tooling and workflows.

Also, we need to distinguish between 2D, 2D+1, and 3D form factors for the end object.

Wood: rotary tool, laser, hand tools
Metal: rotary tool, plasma, electro-chemical etching, non-ferrous metal casting
PCB: rotary tool, innumerable
Plastic: reprap, rotary tool, laser,
Bronze: rotary tool (mabye), lost wax casting
Epoxy Granite: casting
Glass: lost wax casting
Wax/Plastic: RepRap, rotary tool, hand tools, casting.

[objects.reprap.org]
This needs to be turned into table format.


This helps:
[www.epiloglaser.com]

---

If we want to make machines, that's been demonstrated using:

laser-cutters
mill/lathe
cnc router
RepRap
plasma cutter
cold casting
hot casting+tooling
wood, +hand tools
wood, +power tools
etc.

(We may want to wiki this up.)

Wood is great for making stuff that's not cutting metal subtractively or using a hot processes. Raw material is widely available as scrap. People regularly make 2x4 benchtop CNC routers out of the stuff.

And luthiers use 2x4 benchtop CNC routers to create wealth.

---

Regarding screws, available tooling and machine/human time/opportunity costs will drive when people build v.s. buy.

Cabinetmaker: buy.
Bronze Foundry: buy.
Machinist: check mcmaster.com, check salary, build/buy.
Fab Lab: ?

---

Regarding bronze+microwave, I'd start working in a normal microwave, yes. If I can do 8" figurines, I'll be ecstatic. Then I'd buy a microwave leak detector and start hacking.

I can probably do bronze+microwave in my basement, up to 8", at which point I'd have to go to an outbuilding.

Another bronze pathway is powdered-bronze, mixed with a hint of wax as flowing agent, invest in powdered aluminum oxide, cook in your furnace at the usual setting.

---

Regarding plastic pieces as findings on metal, we can swap in granite epoxy when experiment or FEA shows that they fail.

---

Regarding a cnc plasma cutting table; I don't know if I want one of them or a 5x10 CNC router in my basement five years from now, speaking quasi-hypothetically. Going dual-use will require swapping out a 5x10 torsion-box in order to uncover a water tank.

---

Moving aside from my personal tooling goals, I suspect seeding a generic RepLab with 5x10 CNC router will drive out all non-woodworking tools via economic factors, unless the RepLab is a grant-driven shop. Similarly, seeding a generic RepLab with 5x10 Plasma cutter will drive out all non-metal tools via economic factors. Because each one will a need a pool of dedicated tooling for finishing, a flow of wood/metal stock in, and metal filings are a bitch for cabinetmakers. Seeding a RepLab with each of the machines presupposes a lot of space.

Space is cheap in some places.

This is a model to consider: TechShop is a 15,000 square-foot membership-based workshop. It probably provides a valuable opportunity to the community and good value, while allowing the entrepreneurs/enthusiasts who set it up to make house payments.

The folk who set it up bought their machines, rather than incurring opportunity costs by building the machines.

[techshop.ws]
[techshop.ws]

---

This is another model to consider:
[www.vigyanashram.com]

Vigyan Ashram = Tech College/Fab Lab out in the sticks in India, not in a major city.

Vigyan Ashram doesn't have the money for a CNC turning center, but does have the space to set up non-dual use machines.

---

This is a third model to consider: Jin Sato, who helped kick-start Robo-One:
[www.mi-ra-i.com]
[en.wikipedia.org]
He's got a small benchtop mill, a small lathe, and a self-built CNC machine and tiny sheet metal bender/brake.
He's got a typical small-area Japan dwelling. He'd be keen on a dual-use machine, but would probably want to keep handwheels on CNCed lathe.

---

I don't remember if there's any fablabs in megaslums. I'm sure the wealth the machines create would pay for square footage such that we could go to single purpose machines.

---

I don't have a number-based model that would indicate when they'd buy v.s. build ... I think we'd want a number-based model of each machine.

---

Sorry if this post is a bit of a ramble. I agree with you that a RepLab needs a way to work metal. But chopsaws and drill presses are cheap, and perforated wood RBS beam is compatible with perforated metal RBS beam / Contraptor angle iron. And RBS beam, aka gridbeam, is the easiest modular building element to make. And rotary tools are nice and easy to bolt on to positioning systems.

Edited 3 time(s). Last edit at 12/06/2009 02:02AM by SebastienBailard.

I'll have to come back and edit this later but I think this is a good discussion, because there is a balance between being able to do everything and being over specialized. Its also important to recognize what your trying to achieve.

I'll make two points first off, having a machine that can fabricate in a particular manor, dictates the form and function of the objects it makes.
[biorobotics.harvard.edu]

We could design a machines that can be, "A cabinetmaker, a machinist, a bronze sculptor, and a robotics geek have different tooling and workflows." but we could also design a machine that can do all these things with one machine although the process would be different than we would think. A meta machine, a machine to

The second goal is to capture the abilities and capabilities that would normally be contained in a work shop or a machine, into a flexible package that can be replicated and that can also be used to teach fundamental manufacturing techniques to interested people.

Thinking in terms of opportunity costs, availability of resources, user background, and overall purpose, while considering modularity to increase functionality and device distribution.

The problem is that there are few technologies developed that can fit all needs in a single package.

Honestly, I believe we need an iterative approach. A cartesian robot is easier to program, while an inverse kinematic arm can be easier to build but is harder to program. Because we already have a model inherent in a RepRap, I believe that we should focus on a machine that uses in part or in whole, components that are reprapable. The goal is to complement the RepRap with metal fabrication capabilities, thus both machines together can wholly make both machines, thus synergy is formed.

My next step is to experiment with electro-chemical etching, and see if i can make a closed system prototype that can recycle the electrolyte.

One important thing that we can do now however to shrink the manufacturing options we have avaliable is to characterize the complexity of each process, the amount of support materials required, the energy required to do a task, the best/average/worst case precision, the range of materials that can be processed, and whatever else could be problematic.

Lawrence, I'd enjoy seeing the final form. That will not stop me from chattering/taking potshots now.

Sometimes a cabinetmaker will use a CNC router, sometimes (s)he'll use a tablesaw, which is a more fundamental tool for cabinetmaking.

Cartesian robots are easier to program and much easier to check for squareness, cross brace, etc. compared to a inverse kinematic arm. Also, generic inverse kinematic arms don't have the precision of a mill, unless you mean mean parallel robots?

I don't know that they're easier to manufacture but Viktor is keen on them.

I'm very keen to have a go at SDM with my Taig and eventually with Eiffel, if he ever makes it past the napkin sketch stage. I'll be happy if he's a competent CNC router, through-hole driller, gantry mill, ?powder printer?, pick-and-place, SDM and RepRap to begin with. After knocking off such 'easy' tasks, he'll go on to cure cancer before taking a break for lunch.

I've heard some amazing stuff about electro-chemical etching, but it's slooow. A generic rotary tool will run rings about it. Then the ECM will cluck and you'll find a freshly laid steel gear in the nestbox. I agree it's an important approach.

... i'm in a sort of 'evolving phase' about RP and 3D-fabbing since 20 years now ...

My experimenting with parallel kinematics went fine, but the tripod is collecting dust two years now and i'm optimizing and enhancing my CNC-mill instead, because i have ready-to-use software and easy-to-snap-on toolhads for milling, paste-dispensing and laser-cutting.

Next steps to go are sintering with inert gas and lathe-like fabbing and laser supported laminating.

It's more calculating and decising effort and accuracy against complexity, cost and size, what's directing my path, or i would be happy with a common reprap-head bside my mill.

So i think there are many different viewpoints and branches, but no real chance for a single 'perfect' system capable of doing everything ...

Viktor

Edited 1 time(s). Last edit at 12/07/2009 03:38AM by VDX.

I agree that there will be many different paths to take.

One goal I have is I want desperately to work with metals in a safe fashion. Most methods of direct or indirect heating create fumes. My current idea is to use an electrolyte of potassium hydroxide to act as the medium, use a thin wire of epoxy coated magnet wire as the tool head attached to a Cartesian robot. after that I'm thinking of having a water pump pull in electrolyte, spray it in between the work piece and the tool head and then use a vacuum bristle shop vac system to suck up the used liquid. I plan on building a sensor to measure the electric charge on the tool head compared to the tool head so I can have a feed back loop to keep the tool head from bumping the work piece and creating a short. I also hypothesize that I can regenerate the electrolyte by plating a conductive object. This could be useful for a variety of things.

A couple of issues is that I need to build the thing out of hdpe because it is chemically more resistant to acids and bases. I also need to fabricate the wire holder, electrolyte nozzles, and water pathways into a package that can fit on a robot arm.

I also need a cartesian robot. hah... Although to be honest, I can experiment with this idea without the robot.

Right now I've got hdpe welding rod that I'm going to ue to spin/friction weld hdpe scrap plastic into the shapes I need.

I have everything else, welder, electrolyte, epoxy coated wire, and I hope to have positive results by christmas.

I'm afraid I'm about to kill the conversation, so to get back on topic.

It sounds like you really want to add a router drill to the RepRap, since it would satisfy the majority of your requirements. I think its an excellent idea, but I think you'll have to use something more rigid than the RepRap, which is why I'm struggling to find non-contact methods of manufacturing.

There are already some guys who are building RepStraps using perforated aluminum/steel members which is promising because you can feed your Rep Router extruded steel/aluminum to make more perforated members to make more Rep Routers. This still adheres to the RepRap reproducibility ethos.

The other major issue your going to run into is living with your machine. Most suburbanites, villages, community shops have difficulty putting machines in their homes, work shops because of space issues and health hazard issues. These can be addressed but are often overlooked.

Another option is selective re-melting and extraction of plastic using a heated sucker method. Think solder sucker. This would eliminate plastic chips and encourage a fully polymer based construction material toolset.

Er, wow! What great discussions.

Lawrence, I know the RepLab list would love to have your observations and knowledge about RepTab. There doesn't seem to be a ton of information on Marcin's blog, perhaps you could stop by and answer some questions about the control geometry, motors, software, backlash issues and most importantly, how do we build one? :-)

I'm kind of terrified of the notion that a heated lye solution subjected to high voltages constitutes 'safe' metalworking! I mean, of course it's safe if it's in a proper enclosure, but so is nuclear fission. Or cold-working with lathes and mills and recirculating coolant. At the same time I'm strangely attracted to the notion. I'm just inviting someone else to fix the high-voltage lye squirter when it needs maintenance.

In any case, designing a rugged, simple, DfD design for a routing table with a 4x8 work area is a good idea in and of itself, and converting it for use with non-contact tools seems relatively trivial. This is what RepTab, the idea rather than the single table at Factor E, really should be. I don't know about foldability, but at least a modular design that can be disassembled with some work and repaired/replaced piecemeal.

Here in the East Bay we have vast swathes of industrially zoned warehouses that haven't had heavy industry in decades. We have no shortage of useful space, we could use a few recursively built robotic replicators though. Even if some RepTabs are used almost exclusively for plasma, and others entirely for fine cabinetry, there's a point to having a common hardware and software platform for both, much as a Unix machine configured as a server is seldom in practice the same machine you want to do 3-d design on.

Here is the link to the build information. I'm willing to admit that it has a lot of problems, which is why I'm keen on a real community designed successor.
[openfarmtech.org]

These guys have some great ideas about using pre drilled extruded aluminum for the frame.
[www.contraptor.org]
[dev.forums.reprap.org]

And here is some thoughts about using maker beams and grid beams as well.
[builders.reprap.org]

If I could do it all over again, I would have purchased a lot of stock aluminum/steel, had a machine shop drill all the holes with their shiny cnc machine, slap the thing together and use it to make all the drilled grid beams I could ever want.

My suggestion is design a modular track table setup thats 4'x4' or 5'x5' and then design a carrage that can be adjusted for the table size. O and as much as I hate it, I would go metric. I'm tired of imperial vs metric. Heck, I think in mm -> cm -> inches -> feet -> meters already. Its all very confusing at times!

Also, screws have their own problems and with vibration, comes loosening screws. This can be compensated for with nuts that have built in beveled washers, but it might be worth it to find an alternative to screws or minimize them when possible.

Man, if I could find a job out in the bay area I would be down there in a week!

These guys have some great ideas about using pre drilled extruded aluminum for the frame.

Yeah, they're doing kick ass work. I need to pour over their site, I've only given it the cursory once over a few months ago. Basically, we need to bring them under the RepRap umbrella, making their stuff self-replicating and using square beam as much as possible, rather than angle.

Angle bolts to angle on 2 sides of a given angle.
Beam bolts to beam on all 4 sides of a given beam. And you can make it out of wood. Or cast it out of polymer concrete. Or RepRap it.

O and as much as I hate it, I would go metric. I'm tired of imperial vs metric. Heck, I think in mm -> cm -> inches -> feet -> meters already. Its all very confusing at times!

Confusing, but if you're building machines in North America, imperial-sized materials and tooling are cheaper and more convenient to source. This is true for you, and for your North American user-builders.

And here is some thoughts about using maker beams and grid beams as well.

Tim Schmidt. I'll email him, as he's further along than I am. He's using one of the numerous google groups that people use instead of the email unfriendly forum, which is why I had no idea what he's doing.
[groups.google.com]

Also, screws have their own problems and with vibration, comes loosening screws. This can be compensated for with nuts that have built in beveled washers, but it might be worth it to find an alternative to screws or minimize them when possible.

You may want to try Loctite, or some other temporary, semi-permanent, or permanent ?cyranoacetate? fastener adhesive. Or you can pay more to source vibration proof fasteners, of which there are presumably lots, according to my buddy the ex-aircraft mechanic.

Hey guys,

I have a complete machine made entirely from store-bought parts and 1" gridbeam. Another of the Michigan RepRap group members was even able to figure out how to make respectable NEMA-23 motor mounts entirely from beam without drilling any new holes. It's buildable with just a wrench and a hacksaw - no precise measurements or cuts or holes necessary.

Unfortunately, the pre-drilled beam does not seem to be incredibly common (and it's not cheap!). Pre-drilled steel angle appears to be very common, however. I suspect we could build a simpler, stronger, cheaper RepRap using the angle instead of threaded rod as the main structural vitamin. We could print simple brackets to bolt multiple sections of angle together, and to attach the various other parts of the machine.

I founded the Michigan RepRap group (70 members!), continue to organize meetings, and have attended every one so far. So if you have any questions about what we're up to, feel free to ask.

--tim

Looking at the google groups pictures, I like the use of hardware parts! I think it would be a great idea to put up plans for a repstrap/mill that takes up less room than the currently advertised repstrap.

I'm actually jumping around projects because I think that we are about to reach a point where we don't need repstraps as much as we need to improve the percent of reprap that is printable. I'm working on a delta robot design that does just that.

However, let me stress that a solid design and write up for an improvement on the current defacto hardware repstrap standard would be a big deal!

Thanks for the high quality pics.

Tim, these are my current working notes on building a machine using square perforated beam.
[objects.reprap.org]
(And I've been sorting out my tooling before sourcing Eiffel materials.)

At some point, let's think about reverse forking your machine with Eiffel, i.e. merge the designs, parts. and documentation bodies. Interested parties will be developing Eiffel into a general purpose RepRap, RepRouter, RepPowderPrinter, which is why it has a large rectangular chassis rather than the Mendel-like fixed gantry. Also because all the cross bracing may help squareness and sturdiness, when we start thinking about making a machine with 2"x2" or 4"x4" beam, and then using it to drill holes in 2"x2" or 4"x4" to make the next machines.

I see your point on using perforated angle iron, and we'll need to do up a variant using it. Contraptor or mntc.ru have done this, recently and ages ago, respectively. I have no idea if they'd like to write up their work up on RepRap.org or not. I'd guess not, as they're selling kits, and have put lots of work into development. In the happy scenario that they're interested, we can just want to fold in Contraptor's or mntc.ru's work into the wiki, with permission and help and properly cited/attributed. In the more likely scenario, they'd be insulted by the suggestion.
[dev.forums.reprap.org]
[www.mntc.ru]

I suspect there must be thousands of such CNC angle iron machines out in the world, happily functioning as hobby or cottage industry machines. I'm going to focus on square beam first, then drilling square beam. By then someone (probably in Michigan) will probably have an angle iron design up on the wiki.

I think we may also want to do one up in wood.

What are you calling your machine, btw? I had made space at:
[objects.reprap.org]
but I haven't even had a chance to look at your drawings or photos until I followed up on Lawrence's links to your work just a moment ago. (I'm pretty current on everything that happens on the forum in English, everything on the mediawiki, nothing on thingiverse/makerbotforum/bitsfrombytesforum/etc. and some of what's on the blog(s). But none of the google groups which have popped up here and there. I've made a note to plumb them in with an emailing listen-and-post-bot glue after the forum rejuvenation and mailing-listification.)

Looks good. I've uploaded pictures of my machine's NEMA-23 motor mount and leadscrew pillow bearing block here: [www.flickr.com]

The pillow block bearings are simple 3/4" pipe hangers w/ 608 skate bearings JB-welded in place. They are significantly stronger and more durable than they look - for about $0.50 each.

I used drawer slides on my machine, but I think a much better solution would be to use ground steel rod of a slightly smaller diameter than the holes in the beam, mounted in the holes of the beam that composes the frame of the machine using simple (cheap!) plastic bushings. The axis's gantry can then be composed of the same beam, with (cheap!) oilite plain bearings in place of the plastic bushings. You could buy all the necessary parts at McMaster for just a few dollars. Cheaper even than the drawer rails.

I see your point on using perforated angle iron, and we'll need to do up a variant using it. Contraptor or mntc.ru have done this, recently and ages ago, respectively. I have no idea if they'd like to write up their work up on RepRap.org or not. I'd guess not, as they're selling kits, and have put lots of work into development. In the happy scenario that they're interested, we can just want to fold in Contraptor's or mntc.ru's work into the wiki, with permission and help and properly cited/attributed. In the more likely scenario, they'd be insulted by the suggestion.

I don't mind at all publishing Reprap-related Contraptor projects on Reprap wiki - the more people learn about Contraptor the better. More so because it's making use of Reprap developments: stepper motor driver 1.2, Arduino GCode Interpreter.

I haven't had much time to work on contraptions lately, but one of the things I'd like to do soon is to add extruder to Contraptor mini-CNC (http://www.contraptor.org/mini-cnc). This sounds similar to Eiffel and we can certainly collaborate on it, from robot geometry to electronics/software which should handle both subtractive and additive fabrication.

Couple of explanations regarding the choice of materials for Contraptor:

Aluminum was chosen over steel for light weight and being easy to drill/saw. Commercially produced perforated square tubing (that Tim is using) is compatible and can be used in Contraptor assemblies, although it's not exactly cheap. I have not seen perforated steel angle with 1" spacing, but, if sourced or manufactured, it could certainly be used together with/instead of aluminum angle.

Angle was chosen over square tube for several reasons:
- Sliding elements for the angle have very simple design
- 1" T-slot (e.g. 80/20) seemed more economical than square tube, all things considered (material cost, cost to drill and countersink 4 sides, stiffness)
- Weight is a consideration when trying to move the assemblies at reasonable speeds with $150 worth of electronics.

However, I can definitely see a frame built from steel gridbeam and/or 80/20 T-slot and moving assemblies making use of Contraptor linear motion extensions.

I think an open source hardware project should have modularity intrinsic to it; this allows to painlessly swap out the building blocks without cascading dependencies, much as one would do when writing an application relying on libraries and APIs; this also breaks down problems into finite chunks which can be solved by individual contributors. But i'm probably preaching to the choir.


Vitaly
[contraptor.org]

I don't mind at all publishing Reprap-related Contraptor projects on Reprap wiki - the more people learn about Contraptor the better. More so because it's making use of Reprap developments: stepper motor driver 1.2, Arduino GCode Interpreter.

I'll look forward to it.

Aluminum was chosen over steel for light weight and being easy to drill/saw. Commercially produced perforated square tubing (that Tim is using) is compatible and can be used in Contraptor assemblies, although it's not exactly cheap.

Agreed. I'm probably going to source unperforated square beam (solid and hollow) locally, and drill only where I need to, until I've automated drilling.[/i]

When printing, I'll go for total perforation.

When pouring, I'll put rods in the molds for through-holes only where needed. (Unless I've got lots and lots of rod.)

It's all pretty flexible.

Sliding elements for the angle have very simple design
Hmmm ...

I have not seen perforated steel angle with 1" spacing, but, if sourced or manufactured, it could certainly be used together with/instead of aluminum angle.

I think small and large scale shelving bracket may be spaced at 1" sometimes. The holes can be "sloppy", or oversized on one side, which cause slop or non-squareness in a fabrication machine.

1" T-slot (e.g. 80/20) seemed more economical than square tube, all
things considered (material cost, cost to drill and countersink 4
sides, stiffness)

I'll have to run the numbers. I do want T-slot up on the wiki, but it's hard to make with a RepRap - plastic t-slot probably will have zero strength.

Wood square beam is cheap - I've got some demolished cedar deck to mill. Cement or polymer concrete beam may be cheap.

[i}Weight is a consideration when trying to move the assemblies at reasonable speeds with $150 worth of electronics.[/i]
True. I've considered using a bit of aluminum tube or angle for some of the moving bits, but it depends on the configuration.

However, I can definitely see a frame built from steel gridbeam and/or 80/20 T-slot and moving assemblies making use of Contraptor linear motion extensions.

I think the cheapest Eiffel variant will be mostly masonite pegboard and half a liter of plastic widgits.

I think an open source hardware project should have modularity intrinsic to it; this allows to painlessly swap out the building blocks without cascading dependencies, much as one would do when writing an application relying on libraries and APIs; this also breaks down problems into finite chunks which can be solved by individual contributors. But i'm probably preaching to the choir.

You are. It certainly makes design easier, and means the parts aren't "sterile" - you can tear a Contraptor CNC design and use it for a monitor stand, or a gear-cutting apparatus. This is not true with Darwin or Mendel.

On the other hand, and there are nigh-infinite other hands with design and engineering issues, I can also see a monolithic concrete PourStrap (at $90 to $110 per cubic yard) becoming the most popular RepStrap, with people swapping the molds around. But if I design it, I'll make sure it's got a one or two nicely spaced through-holes to bolt to.

Actually, on the subject of plastic T-Slot, Erik de Bruijn made some 15mm variants on the MakerBeam design which he printed on his Darwin. By all reports it was reasonably strong, certainly strong enough to hold a bracket and screws and probably rigid enough to form the framing elements of a non-contact tool like a RepRap.

25mm, a more usual size, would be time consuming to execute but quite strong indeed. 10mm, which is the MakerBeam standard, is a little small for the resolution of current machines, and beams printed in this size can be snapped fairly easily.

There's been good work out here in the Bay on modifying a ShopBot (and by extension any similar router) to drill Contraptor brackets, and work on automated GridBeam wood drilling is soon to come. This is an area where we can expect to see a lot of development in 2010; the interest has clearly hit a critical mass.

SebastienBailard Wrote:
-------------------------------------------------------
> I don't mind at all publishing Reprap-related
> Contraptor projects on Reprap wiki - the more
> I'll look forward to it.

Should I just create a Contraptor page on the wiki then?

> Agreed. I'm probably going to source unperforated
> square beam (solid and hollow) locally, and drill
> only where I need to, until I've automated

I document the same approach (centerpunch all, drill only what you need, as you go), even though my angle is all drilled. But I've heard on multiple occasions that it's essential to drill all holes upfront. Even though this was in reference to GridBeam, I'm pretty sure it applies to Contraptor as well.

> Sliding elements for the angle have very simple
> design
> Hmmm ...

OK, relatively simple - comparing to something that would slide on square tube or T-slot and be easily adjustable.

> I think small and large scale shelving bracket may
> be spaced at 1" sometimes. The holes can be
> "sloppy", or oversized on one side, which cause
> slop or non-squareness in a fabrication machine.

Yeah, it's typically oddly sized

> Wood square beam is cheap - I've got some
> demolished cedar deck to mill. Cement or polymer

Sam's and mine mutual friend has made quite a few sticks of GridBeam on his Shopbot, and they were pretty impressive. Definitely useful for framing, shelving, and modular furniture in general.

> On the other hand, and there are nigh-infinite
> other hands with design and engineering issues, I
> can also see a monolithic concrete PourStrap (at
> $90 to $110 per cubic yard) becoming the most
> popular RepStrap, with people swapping the molds
> around. But if I design it, I'll make sure it's
> got a one or two nicely spaced through-holes to
> bolt to.

That would be very interesting to see. You could certainly do epoxy granite one - I've been mulling over casting 1" thick epoxy granite plates of various sizes, with pegboard hole pattern, to go with Contraptor.

---

Vitaly
[contraptor.org]

Should I just create a Contraptor page on the wiki then?

Please do. You may want to use the [[Example]] page as a template.

I document the same approach (centerpunch all, drill only what you need, as you go), even though my angle is all drilled. But I've heard on multiple occasions that it's essential to drill all holes upfront. Even though this was in reference to GridBeam, I'm pretty sure it applies to Contraptor as well.

Any modular set of holes, yes.

It is necessary to point out it's unnecessary drill-press time if the machine builder is certain (s)he's building a single-purpose machine and not going to do a tear-down and reconfig once a month. You're doing this, but I think I should.

OK, relatively simple - comparing to something that would slide on square tube or T-slot and be easily adjustable.

Ah. Understood.

That would be very interesting to see. You could certainly do epoxy granite one - I've been mulling over casting 1" thick epoxy granite plates of various sizes, with pegboard hole pattern, to go with Contraptor.

I've been keeping my idea-slush-pile on the wiki. Now it is time to get cracking.