What I'd make with a rapid prototyping/3-D printing machine
Kragen Javier Sitaker
kragen at pobox.com
Wed Oct 11 17:54:35 EDT 2006
On Fri, 7 Apr 2006 13:08:18 +0200, Dave Long wrote:
> > Suppose I had a machine that could manufacture any three-dimensional
> > shape, down to a few microns, but only out of some single rather
> > boring material; what would I do with it?
> Since I now have a machine that can manufacture any three-dimensional
> shape, but only down to many tenths of a mm, and out of a rather
> brittle plaster material (we are using it to help produce patterns,
> with the production material being silicone, so quick builds are more
> important than the material properties), I figured it would be good to
> revisit this post.
Very interesting! Do you have a good handle on the per-piece cost?
Is the material porous?
> Pretty easy
> > Soma cube --- with faces that fit together.
> > "Do-nothing" gift-shop toy. (I don't know if this piece of junk is
> > still available for sale or findable on the web. The one my family
> > had was carved from wood; it consists of a crank attached to two
> > sliders at right angles.)
> can you describe this a bit further? I've done a geneva stop model,
> and a Peaucellier linkage (which seems to have impressed Kelvin a good
> deal more than any of us), so this device shouldn't be any trouble
Wow, those sound very impressive. I'll have to look up the
Peaucellier linkage next time I'm online.
The base of the toy is a square, with two grooves carved in a cross
pattern, extending to the edge (fig. 1).
| | | _____ _____
+--+--+ / \
| | | /____\
The two grooves are wider at the bottom than at the top (see
cross-section in fig. 2). Each one contains a slider with the same
shape; the sliders can slide up and down the grooves, but they cannot
slip out the top of the groove.
The two sliders are connected by a rigid linkage, pivoted at each end,
which keeps the distance between them constant. This both prevents
them from sliding out the end of the grooves and from colliding with
one another at the center of the block. The rigid piece constituting
the linkage is extended some distance beyond one of the sliders and
fitted with a crank handle.
By rotating the crank (in a rather elliptical pattern) one slides the
sliders back and forth in the grooves.
> > A projective plane, out of mesh.
> Hilbert curves, klein bottles, menger sponges
Those all sound fairly compelling. Have you done any of them?
> > Pans for things like waxing printouts --- similar to a sumi stone.
> although the build costs mean it's probably easier to build these out
> of sheet stock. Custom cradles and jigs for printouts, on the other
Sheet stock is sheet metal stock, right? You're probably less likely
to cut yourself on the "print" button than on the sheet metal brake.
(It's just incredible how eager steel is to form razor-sharp edges
when you cut it, isn't it? It's as if it wants revenge.)
> > Buttons for clothing.
It's not too brittle for that?
> > Parabolic reflectors for sound, light, and radio waves.
> > Molds to mold clay into shape to cast e.g. metal.
> There is also a refractory powder available for our machine, which we
> hope to try out Real Soon Now.
That sounds exciting. But you can probably do a lot of things with
> > Carrying cases for cell phones, business cards, earplugs, any number
> > of personal items that need a little protection.
> somewhat sacrificial protection, at least
If they need protection from dirt or scratching, rather than impact or
compression, it might work OK.
> > Things with text inscribed on them. It may be possible to inscribe
> > text fairly small --- 10-micron resolution allows 0.7 mm line height,
> > so 360 lines of text per inch, or 0.2 points. Large text allows
> > signs.
> large text, at least. In general, this is a very good process for
> surfaces that need complex relief. (printing out topo maps is a nice
> application -- even for Swiss topography, though, one must exaggerate
> the vertical scale by 4x or so)
Jennifer must be in heaven!
I haven't seen grayscale barcodes, perhaps because grayscale printers
are so rare. But in theory you could put more bits of information
into each pixel that way. If 3D printers and scanners become common,
perhaps we can use the third dimension to encode more bits per pixel
and have relief barcodes.
> Maybe possible
> > Fluidic integrated circuits. (Maybe. Surface characteristics may
> > make this hard.)
> Judging from the Exploratorium's model, these ought to be sufficiently
> macroscopic to work. I have printed flutes and whistles that work,
> which are the pneumatic equivalent of white noise generators and
> bandpass filters. (the warbler in the whistle is embedded as printed
> ... but the solid warbler in my current .STL are too heavy. would a
> whiffle-ball warbler warble well, if whiffle-ball warblers wouldn't
> warble worse?)
Have you tried them? If it didn't work right off, you might be able
to improve the surface smoothness somehow --- running streams of
abrasive-bearing water through the channels, perhaps, or soaking the
whole thing in molten wax, then taking it out of the wax and keeping
it hot while the wax drains out of the channels.
> > Fresnel reflectors.
> given the surface accuracy, more suitable for concentrating than
Might depend on what you're reflecting. Audible sound could work.
> > Lego-like toys that fit together.
> > Lenses, perhaps. At least, molds to cast lenses of other materials.
> At least, molds to get the rough form.
How good is your precision? Legoids and other "press-fit" things
require fairly tight tolerances.
> Maybe patterns of lenses, allowing one to polish the molds instead
> of the castings?
That's an interesting idea.
> > Combs.
> > Innocuous engines --- a very small "internal combustion" engine that
> > runs very slowly on vinegar and baking soda.
> > Rubik's Cubes.
> the spider at the center of the cube might be difficult
Because of the stresses?
> > Handheld mechanical calculators similar to the Curta. Perhaps even a
> > handheld programmable mechanical computer. Slide rules, of course.
> slide rules, anyway, with the advantage of engraved scales. (although
> I am not sure this is much of an advantage over laser-printed scales)
> For curta-like devices, see the note below about mechanical logics.
> How about helical slide rules?
I hadn't heard of the idea of helical slide rules, but in retrospect
it seems like obviously the right thing.
> Things that would need stronger/flexible materials or higher resolution
> Pretty obvious. Also, an unfortunate dichotomy due to resolution
> constraints is that one can print parts already assembled in situ,
> or one can print parts that will fit tightly together, but not both
> at the same time.
That's interesting --- why not?
> Are there mechanical logics that tolerate a great deal of slop?
Slop in the sense of backlash? I think so. In a sense, tolerating a
great deal of slop is the whole point of using binary, no?
> > Screws. And tapped things.
I'm sure there are some kinds of screws you could make, although maybe
they wouldn't be as broadly applicable as metal screws. If the
material is plaster-like, though, I imagine your surfaces have a high
coefficient of friction, so Acme threads might be better than the
usual triangular kind.
> > Mechanical clocks and watches. Perhaps I could make a 28-hour-day
> > mechanical watch.
Not even clocks?
> > Fans. The kind with blades.
Fans can turn fairly slowly and work with fairly thick blades.
> > Boats. Floats.
You can't print hollow things? Or you just wouldn't be able to stand
in the boat?
> > Buildings that regulate their temperature by breathing.
I imagine that's a matter of scale rather than resolution, no?
> > Anisotropic structured 3-D composite materials --- like honeycombs,
> > but simpler and more nearly isotropic. Closest-packing-of-spheres
> > lattices might be stronger than foams of similar density. This is
> > most interesting if the strength (or stiffness, etc.) and cost of the
> > resulting material is an improvement over already available materials,
> > but it's probably a good technique for interior parts of a wide class
> > of objects to be made in this fashion. By deforming the tessellation
> > or using a different crystal structure, it may be possible to produce
> > materials with desired anisotropies; by doing this in a way that
> > varies throughout the substance, it may be possible to make a material
> > stronger in some places than in others.
Clearly it's more practical to just use a stronger material with a
simpler structure, but I'm interested in how much we could gain by
this technique. I mean, It's hard to believe bird skeletons are made
out of limestone.
> > Generally, clockwork things that would be unacceptably expensive if
> > assembled by hand. Every rotating joint, wheel, and gear can run on
> > ball or roller bearings to lengthen its life. Every nut can be a
> > ballnut (with ball bearings inside) if it's advantageous. With some
> > 3-D printing techniques, it's possible to make permanentlyhermetically
> > sealed enclosures, which can be useful for extending part life in
> > grotty environments.
How big do gear teeth have to be at 0.5mm resolution? It seems that
ball bearings with 0.5mm roughness would need to be 1cm or more in
diameter to be worth using.
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