instead of tape why isn’t he using little wheels to hold the platform up?

hi folks,

neat to see this up here! :)

to your questions, there are definitely better ways to build an x/y axis, if you have a set of precision parts available (like ground rods, belts, etc). the goal of this project is to set all that aside and say, i’d like to build a 3D printer that can be *entirely* laser cut (and therefore, also likely printed), with the only vitamins as nuts and bolts — things that would be available at the simplest of hardware stores. the reason i’ve undertaken this design goal is to make the project widely accessible, meaning that as long as you have access to the laser cut (or, potentially, 3d printed) parts, you could create the entire device in an afternoon with nothing more than a box of standard screws and some tape. the *ultimate* goal of keeping it accessible is that 1) the parts would be easy to come by, 2) people of limited technical skill could easily assemble it (say, in an afternoon, as a project with your kids), and 3) it would be extremely inexpensive compared to similar technologies, meaning that even very low income folks could afford it — in this case, the entire axis featured here is $7 total ($1 in material, $1 in screws, and $5 for the stepper). Using acrylic brings this up to about $10, but I’m using the hardboard to prototype the design and work out the bugs.

ultimately, in terms of its use for the open sls 3d printer, you can think of it in terms of a bootstrap device — it may not be terribly high precision right now (about 0.3mm accuracy, in its current configuration), but that’s easy to change. And, like a repstrap to a reprap, you could inexpensively print out a better, more precise linear axis upgrade design using the linear axis as a component of printer itself.

i tested a bunch of other designs for a complete 2-axis x/y system using linear slides (even using idler wheels, someone mentioned this earlier), and these are detailed on the reprap builders blog in earlier posts. each had issues with shearing or binding, and this new design is just fantastic in those respects. with the proper spacing between the gantry and the linear rails, things seem to work really well — far far better than you’d expect. there’s definitely going to be some backlash in the system, which i haven’t fully characterized yet (to see if its relatively constant), but that’s mediated by the fact that for rastering (for, say, SLS) you only go in one direction, then back in the other — so you never have to deal with any backlash issues, only monitoring endstops. i can only imagine the motion will get better with a better aligned gearbox — i just eyeballed this one, so its fantastic that it works at all! :) i have also thought of making a version with an etched encoder strip on the linear axis, so that you could sandwich the axis between a cheap opto endstop and have an okay encoder available to you.

the real creativity and innovation in this project is seeing what you can do when you limit yourself to a given set of build tools and media, with the (possibly lofty) goal of creating an accessible, inexpensive (under $200), and easy to assemble 3D printer for novice makers everywhere to enjoy.

(if other grad students or folks with access to maker tools with an engineering/computer science background are genuinely captivated by this project and would like to help the design and building efforts, please feel free to send me a message — my phd thesis takes up a great deal of my time these days, and extra helping hands who are genuinely inspired by these ideas would be wonderful!)

be well

@peter

While I do understand that you want to keep the complexity and cost down, I still don’t think that’s an excuse to make a subpar system.

You are already using exotic parts and tools (lasers/steppers) so I really don’t understand why you aren’t using at least things like roller blade bearings and such.

In any case – keep up the good work!

Where can I find $5 stepper motors?

i like the idea, if you have a laser cutter it would be very cheep, and a 3d printer unlike a mill or a router he does not need to be repeatable to .001″. he can probably get up to about +-.02″..good enof

@bud

+/- 0.02″ = +/-0.51mm.

I don’t think many folks would be happy with 1mm misalignment registration steps all over their parts…

The main concern between a mill / router vs 3d printer / laser cutter is whether there is a significant load on the head during “processing”. Mills / routers need to be incredibly rigid to retain their accuracy and repeatability under load (i.e. when the head is cutting).

For me, the repeatability on a 3D printer needs to be at +/-0.1mm = +/-0.004″ to be useable.

oh.. and this might sound like a *crazy* idea, but trust me its not:
since your envelope is rather small, you could spring the whole head to one end of the rack. you would effectively have zero backlash, and the modification would be two holes and a spring.
You just need to find one that has a pull force just a bit more than the weight of the head and stepper. a letter weight scale (perhaps 2) might about right.

This has been done on a few machines I have worked on using pneumatic cylinders at low pressures rather than springs.

I get lots of stepper motors by dismantling old printers and scanners. Friends of mine know that if they are getting rid of an old printer or scanner that I’ll tak eit off their hands.

These are also a good source for ground rods. I’ve got a selection of rods from 6mm to 11mm in diameter from various devices. The trick is finding two identical – easiest if you can find two very similar printers as each maker uses a different size.

OK so instead of springs what about something like surgical tubing? I have no experience with 3d printing but I do have a little with molding and have successfully made “stretchy” tubing in a pinch using a straw and wire for a mold and RTV as the fab material.It didn’t last long but it was off the shelf material.If you are going to be3d printing you are going to be resourceful in materials acquisition anyhow so why not get started right away !

just continuing the ideas set forth on these replies. driving a single gear from the stepper will give you the biggest bang for the buck. those other gears can just be tensioners, and in all R&P tables I’ve seen, any extra “wheels” on the rack are independently adjustable. every iterative design I’ve seen progress has settled on that solution, and for good reason, too. driving the pinion independently of the other gears does two things, you can design different ratios for your motor without drastic alterations, and it makes tramming the assembly easy enough for a 10 year old.

wonderful work, btw. I love seeing these things on HaD.