Ok... so I've given up on having enough skill to make something accurate enough on my own that'll get the job done... I'm sticking with my general design for my first reprap, but I just don't have the skills (or the tools) to make a proper repstrap of that design. So... I've switched gears...
I'm now creating a much smaller repstrap, made out of, you guessed it, Legos! I've taken my original Y axis and I'm using it as my Z axis to mount my extruder head on. (It's a little loose to the board, I may need to take out the flat 1x's that I have on the very bottom, or just tape down a piece of cardboard or something to level out the wheels)
I've created a sliding horizontal axis, using the smooth flat pieces, and all four of my 'rack and pinion' racks (1x4). I'm using the smallest gear they've got (1x1 sleeve that fits over the axis with about 6-8 teeth on it) for precision; I know how much quicker the rack and pinion is, so I'm gearing it to be as slow/accurate as I can.
That's going to sit ontop of a 'carrage'. Geared for 4-wheel drive, I'm relying on gravity, the tire treads and carpeting, for the accuracy here. I don't have enough small wheels left, so I've got some monsters on it, and I really don't want to try rigging up a screw drive to them. (I've 5 other types of wheels, all in pairs, none in sets of 4!) I'm taking the time to rig it for 4 wheel drive to help keep it reliable. (Now I just gotta keep from turning my lego repstrap into an rc truck!)
I'm intending to have a small, fast prototyper, relying on the accuracy of the Lego bricks, that will then prototype the parts, with the accuracy I need, for my +- design. (I'm also beefing up the supports on the XZ axis, moving to U shaped shelving support brackets over steel rods)
Sounds good! :-)
We await blog pix with keen anticipation!
Yes! Pics! Lotsa pics! :-D
The glue seems to be holding fine on my motor, and I've successfully run the rack & pinion stage back and forth (and off the end, and back on it, though I haven't actually launched it yet...) I'm currently trying to use a 2x axle, but it's not performing as well as I'd like... The 2x axle's, unlike every larger axle, have 'cuts' or 'grooves' in them running around their circumference (in the center of each of the '1x1' areas...). In addition to that, the round axle 'coupler' thingy, was glued to the motor with the 'glob' technique, so the bottom 1/4th to 1/3th of the couple is filled with glue, preventing the axle from fully seating the full 1x1 portion. Between the two of them, the axle 'wobbles' slightly, though I've been able to minimize, and nearly eliminate, that wobble by compressing the glue inside the coupler (smashing the axle into the motor as hard as i can, without breaking anything). I haphazardly ran the stage back and forth (and off end a few times), and with all the excessive abuse I gave it, i didn't see the wobble return.
After lowering the speed a little (200ish), and properly calibrating the limits (that are not yet installed), i ran it back and forth about 15 times, and it seemed to 'always' stop at the same spot, showing that it's not drifting or anything. The first time I ran it, with the wobble and at full speed (250), I violently slammed the slider back and forth (found out the software registers the slidermovement without releasing it...), and it did end up drifting off the end (probably 3-5 rack teeth in 45ish seconds). I think the wobble was the real factor there; on a few initial tests (manually moving the stage with the motor attached but not plugged in), the pinion gear wobbled enough to skip and even seperate from the rack.
Sadly... my 2.5 year old canon digital video camera died about a month ago; thankfuly there's a 'recall' on the part that appears to be broken, and they're currently emailing me a shipping label for what will, hopefully, be a free repair/replacement.
Next I've got to decide how/where I'm attaching the limitor switches to the stage, and then build it up a little more so that it clears the motor. In the mean time, I'm going to glue the coupler to the motor for the 4x4 stage, and figure out how I'm going to clear the monster wheels.
It may just be the science fiction writer in me, but with a few minor adjustments, a robotic arm for grabbing, a second rack & pinion axis, steering for the 4x4, attaching the Z axis to the XY axis, solar panels for power, and solving the whole 'replicating circuitry & components' thing... drop a couple (for initial redundancy) on the moon, or mars, and you got a self building colony! So who wants to be in my 'next' book? moon or mars? nasa? esa? china? private company? military? or opensource community?(I do have a model rocketry background... and I do have plans for a rotary axis replicator for extruding rockets (body/fins/engine mount/nosecone/etc)...)
The wobble bothered me enough that I took the coupler off the motor and re-glued it, with the axle inside the coupler; and this time I used epoxy so I wouldn't have to wait as long, and did both motors at once. I've also helped to eliminate the wobble by running the axle through a technic 1x2 to stableize and center it, before hitting the rack/pinion setup (motor->technic stabelizer->pinion/rack). I mounted the limitor switches on technic 1x4's using the same trick I used before (wire through the hole), and placed them on either end of the moving axis, pointing inwards. I placed a 2x2 block (with 2x2 flat on top for extra reach) in the center opposite the motor to trip the switches.
I fired it up, and got lucky on getting the min/max on the right sides. It calibrated just fine and runs back and forth without problem, at 200 or less. I cranked it up to the 250 range and it started 'skipping', though I'm not sure if it was the motor stuttering/getting stuck, or if the pinion gear was slipping (which I don't think, given the tightness of the design). Even at 200, though, I think it'll give the extruder a run for it's money...
I'm working on the 4x4 axis now, and I've decided that the motor will directly drive the center axis, and will sit 'inside' the chassie. I've also decided that the platform for this stage will sit above the top of the tires, to give full clearence to the axis sitting ontop of it. I've got the motor 'semi-mounted' with the two inner gears around it; now I've got to figure out how I'm mounting the two outer axles, with the four wheels on them, and setting the overall width of it. I'm considering the idea of giving each wheel it's own seperate axle, and tieing the left and right together with inner pair of axles, giving each 2-3 gears (depending on if the motor axle ends up with 1 in the center or 2 on the edges to directly transfer to the gears that transfer to the wheel axles...)
While the 4x4, in it's current rendition, isn't the most accurate, I'm hopeing to eventually replace the wheels with pinion gears and run it accross two rows of track (which , I'm hopeing, will be reprapped rack, even if I can't say it three times fast...)
Oh, and the Z axis fell off the board (not while running or anything, just sitting there), so I'm going to have to come up with some legitimate way of securing it when I reassemble it... (no real damage, but I've got to eliminate the wobble/inaccuracy that gravity was compensating for before.)
Great stuff, cat!
Wouldn't it be hilarious if Lego came out with a repstrap replicator kit based on your work? :-D
The biggest thing that's missing out of the 'programmable' kit i've got here is steppers and/or encoders... I've actually got one or two lego limitor switches (though they've only got two wires, so I suspect they're normally open), and a bunch of lego dc motors. That, and the lack of rack... (I think, once I've got both polymer and support material working, my first project is going to be prototyping lego-compatible 1x4 rack pieces...)
I also don't think they could get away with selling the heated extruder head, but they could do room temperature syringe type stuff...
Short of the rack&pinion&shaft&motor&electronics/etc, I can put out my OWN repstrap replicator kit! Using the LEGO Digital Designer, they let you order 'one off' kits, that you design yourself... You specify the parts, the software creates the instructions and lets you set up a 'picture' for the cover of the box/manual. If I can get them to sell the couple of things I need that are missing, it'll be a 'one stop shop' for everything but the electronics/motors...
Once I figure out a Z axis, and meticulously rebuild the thing from scratch so the instructions make sense!, I'll blog it and post a link to the file so others can snag it (and look into buying what they need/can!, though that might best wait till I get the rack&pinion/etc supply resolved...)
Wonderful! But I think we need a level of cohesion and future-proofing at the start.
1. Platform independence; specifically no reliance whatsoever on anything that will only run under Windows. For example, Repstraps really do need to be driven by the same standard Java software that RepRap 1.0 "Darwin" will use. This also means ensuring that LEGO Digital Designer is not essential long term, as it's neither Open Source nor platform independent (though it is, for the moment, free). There's no harm in using it once-off to bootstrap things though.
2. Using the token ring/I2C electronics. Now that we're close to having a standard PCB for each node, that should be straightforward. And it's essential that we don't get stuck with a design which does not have one controller per active component, because such a design is not scalable.
That said, this is brilliant madness :-) If you really can make a working Repstrap with Lego that is capable of producing (say) the RP parts for the extruder, then that radically increases the ease for people getting started.
While I am dabbling in rewriting the software in .net, I'm currently running everything through the java software (and the pc that's running my reprap isn't even .net compatible!)
The LDD software is only used for the design process, and it produces (with some finageling) printable/html Lego style instructions. The whole concept is to use Lego's for this repstrap, so I don't feel that relying on Lego (from the manufacturer) software/tools goes against it. It's only essential in the sense that it is 'needed' for the Lego RepStrap device, and then only if you're going to be making changes. I'm not sure exactly how it works, but I believe others can purchase my 'kit' from Lego, even without the software. The software would only be needed for 'updates' or 'changes' to the kit/order...
I'm also planning on sitting down and re-engineering this entire prototyper as a reprapped device (in aoi), maintaining the same design and sizes so that you can swap parts in, one stage half at a time. I'll even try out the idea of making the prototyped parts compatible with legos, though I might only do the nubs and make them 'bottom' only.
Again, I'm following off the site, and using the seperate controllers on there. I'm putting them on a single board for 'neatness', but it's still all the seperate controllers, wired up on the board.
I've got some lego dc motors that work great, and have more torque than the steppers I'm using, but I don't want to deal with that whole mess, so I'm going non-lego stepper motors.
As crazy as I get, I try to stay true to the whole reprap philosophy... That's why I'm not building a repstrapbox :) I haven't physically checked the size of the extruder parts to ensure that they're small enough to be protyped on here, but I'm pretty sure they'll fit straight, and almost positive that they'll fit on a diagnle.
Oh, and I've designed a Z axis, it comes out to about $19, so I'm up to around $40 for (most of) the legos... All that's missing is the rack&pinion&shaft... Currently, my design takes 10-12 1x4 rack, 3 pinion gears and 3 shafts (two are 1x4, the third I'm still sizeing/designing...). I think the two 1x4 shafts are available on their own, but the rest isn't...
Excellent news! And - as I said - using the Lego design software to bootstrap the whole thing seems absolutely fine. I take Simon's point about Lego not being happy if we use Lego to put Lego out of business. But, having got an entirely undeserved reputation for being a Marxist merely because I quoted him (I'm actually a sort of libertarian liberal), I shall now quote V.I. Lenin: "The good capitalist will sell you the rope that you use to hang him."
This just goes to show what a noxious person Lenin was. However, I wonder how many rolls of film were used during the development and intitial marketing of digital cameras...
Frankly... at 8-50 cents a piece... and a few hundred pieces per kit... I don't think they've got anything to worry about right now...
Sure I'm planning on trying to make some 'lego rack' with my prototyper, but only because they won't sell it to me! I'm not going to spend hours babysitting my prototyper to produce a flat 6x8 piece (with ALL that support material to get the proper nubs on top and circles on the bottom), when I can buy it for $0.37. (and we've got a ways to go before we've got the accuracy to print the Lego logo on each nub!)
So I finnaly decided the 4x4 was the X axis... (X as in 4X4...) and I got it built up, and mounted the Y axis on top of it. I don't have the limitors wired up to the X axis right now, but I've built front and rear bumpers for it that I'm planning on installing them onto. I'm pretty happy with everything, though there are two big problems I have to resolve...
#1 Wires... They're a bit of a mess, and keep getting caught on the lego nubs, so I'm going to have to figure the optimal layout for them, and how to secure them to it.
#2 Stepper Power... When I purchased my unipolar steppers (to replace my bipolar ones/to match the unipolar controller i had made), I bought the cheapest ones they had at Futurlec... Figured if I could get it to work on those, you could use any real 12v steppers to do the job... The Z axis seems to work, and the Y axis does (so long as I keep it at 200 or less), but the X axis is having trouble... The gearing itself forces the motor to run at 200 or less, the weight of the X axis itself brings it down another 50, and the Y axis on top of that brings it down another 50... Oh, and it doesn't have enough power to drive over the cat5 cable i'm using to feed it power/control... So... I'm shopping for a new stepper motor for the X axis... Futurlec has been out of stock of their 2nd and 3rd stepper motors, so that leaves the $5 one on the bottom... little bit bigger than I would like... so I've got some shopping to do!
Back to the drawing board!
... or actualy... off to the LEGO Digital Designer...
I found out that LEGO finally came out with something of a LEGO CAD program, and interfaced it with their online store... The only real problem (aside from the instructions being based on the order you place the pieces, and copying a bunch of pieces at once doesn't preserve the order they were placed...) is the lack of any rack (or pinion) in either the LEGO Digital Designer, or the web site.
Conviently enough... I found 12 lego rack pieces (to go with the 4 I've got) on EBay for less than $9... (half the cost is shipping from uk, and I doubt you could even find a $9 LEGO kit with a single rack in it, let alone 4 to 12...)
I sat down and redesigned my Y (rack & pinion) stage in the LDD, leaving out the rack, pinion, shaft, motor and limitor switches. I wanted to do it with some consistancy (though the color selection is a bit off, so I'm going to have to revisit that and try a different approach...) and use proper pieces (ie: real flat pieces instead of the fighter wings I've been using...) I then went so far as to copy the whole thing, twist it 90 degrees, and plop it ontop of itself. I then decided I didn't like everything all together how it was, so I seperated the three pieces where they don't actually connect... (bottom of the X axis, top of the X+bottom of the Y, top of the Y axis...) I then futzed around with it and got frustrated and fed up and decided I was done for now... (it's there, but the build instructions suck... the 2nd axis is screwed up since i copied it all at once, and lost the order that I placed the individual blocks...)
I sent it off to Lego, and it came back around $22.00 for the whole XY axis setup (both axis, minus rack&pinion&motor&shaft) I'm going to brainstorm over a small Z axis I can place on top of the XY axis. Since I'm placing the axis under the work surface, and not on the extruder head itself, I can consider rack&pinion for it (being just the worksurface, it might be light enough for the motor to hold it still, even without power. Either way, if it does crash, it'll be seperating the stage from the extruder head, so there shouldn't be any real damage...)
Got an email back from lego... they do sell the extra parts... just not on the main web site... (and not in 1-off quantities)...
$10 gets you 12 rack (exactly the amount I plan on using) and 10 'threaded rod' pieces... (I'm thinking of trying to harness those for the syringe extruder...)
$10 gets you 100 1x1 gears... (you only need 3... but they don't sell them in quantities less then 100, unless you go to the regular web site and get the 'gear' kit for about the same price, which only includes 2 of the 1x1 gears.....)
$10 gets you 100 of the 1x1 axle coupler thingies (roundish on one side, +ish on the other... slips over the + axles..) I'm using these to help secure the axle to the motor (more glueing surface), but they're probably optional at $10 a pack...
I haven't gotten much more work done on the kit (i'm redesigning the Z axis... trying to decide if i want the motor high on the stationary part, or low on the moving part... it's more effort/weight if it's on the moving part, but it's less stable/more top heavy with it at the top of the stationary part (especially when the platform is down all the way...) I'm thinking of trying to mock up my current design with what parts i've got and testing to see how well the motor works... Of course, i've also got an order for 3 more (hopefuly more powerful) steppers... so hopefully that won't be an issue...
I forgot to mention WHERE they sell them!!
They get away with the 100 quantities by being an educational site and selling mainly to teachers/schools...
I think I've finalized my first attempt at a Lego RepStrap XYZ Stage, I'm pretty happy with it, I just hope it doesn't wobble too much from all the momentum! (maybe i should glue its feet to a board or something...)
Still don't have the best of solutions for the rack & pinion setup, but everything else is pretty good... (though I've only got access to 1x2 technic bricks instead of 1x4's, so i'll have to deal with the middle pin on the limitor switches...) 238 pieces at $41.14... and I didn't notice any difference when I merged the two kits together (it wasn't an exact match, so there could be a $1-2 charge per kit, but I was coming up with 40ish between the two before i put in the mounts for the limitor switches on the Z axis...)
The data files/designs are freely distributable, in fact when you upload it to the Lego site you agree to allow your site to be freely distributable. My only concern lies in the instructional output generated by the LDD... I'm guessing they made it generate a web page with a folder full of pictures so you could easily post it and share it with people, and it is using the LDD as a specialized rendering package, but I only "own" the design itself, not the models of all the bricks that were used to render it... I've emailed Lego support about it, and hope to get an answer sometime in the next week...
Frankly, the instruction generation sucks in it... If you've got the software running, and can move/zoom, it's ok... but other than that... it's brainless... If there's no issues with posting the pictures/instructions, I'm going to sit down and painstakingly put together a proper set (actually rotating/zooming to look at the part(s) being placed on that step!) and then post it.
I'm still hesitant about placing the actual order... I want to ponder over the design some more... and see if I can't harass Lego enough to sell the few extra pieces I need to complete it!
I placed the order... I did a few last minute modifications to include the required Lego dude, along with a nice little platform for him to stand on (on one of the XY axises) with two joysticks and a set of computer readouts! I also gave up trying to wait them out to get them to add the extra few pieces I needed; I can always add that to a future version if they ever start selling them!
I don't expect them to ship it till after XMAS, and I didn't spend the money on shipping, so I won't get it till next year... but I'll have my new motors prepped (wired and glued) and I'll be ready to start the year out right!
...now I just gotta stop putting off the whole extruder head thing... I've got a syringe, so I'm thinking I'm gunna start with that type of extruder, and see if I can't get some good support material working in it... maybe see if I can't extrude a few things in plaster or something...
I wonder what the Lego folks would think of making a machine that could also make the Lego parts themselves though.
My kit has arrived!!!
I gotta come up with one more motor<->axle mount and I'll have everything for the XYZ figured out! (and all in lego bricks/plastic, all reprappable!)
Speaking of which, I've got some pencil drawings of parts to reprap the XY axis; I just need to decide on some sizes and put them into AoI.
Time to get some pictures and footage!
"Time to get some pictures and footage!"
Can't wait ;-)
If you put the footage on YouTube we can link to it from the RepRap wiki videos page.
How much did it cost again? & do you have a spec sheet for the kit?
Postage & Handling 6.95
Order Total 53.99
does not include the rack pieces ($10 for as 12 pack, need all 12 but none of the worm gear pieces), nor pinion gears ($10 for 100 pack, only need 3......)
if by spec sheet you mean list of legos in the box? no, don't think so... I can, however, share both the digital designer 'cad' file, and the html-based instructions it generates for the kit...
...I haven't posted either yet because I want to make sure the thing works before anyone else goes and spends $50+ on it :) I do plan on putting them both up later tonight/tomorrow once I've got my entry together...
It's a 'steal' @ that kind of price.. can't wait for further details...
regards (& some amazement),
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