Hello listers,
The following Stanford press release from a couple of weeks back is a good
survey of the rapid prototyping state of the art. The release is long, but
at the end you'll find a number of URLs which may be of interest.
Enjoy,
Bryan Bashin
----------------------
> 8/25/99
>
> David F. Salisbury, News Service (650) 725-1944; e-mail:
> david.salisbury@stanford.edu
>
>Industry reps, academics swap theories on rapid design, assembly of
>prototypes
>
> Suppose, as sometimes happens in real life, your 6-year-old daughter
> has just ruined her favorite Barbie doll's face with nail-polish
> remover. Though you've gamely tried repainting the lips, eyes and
> eyebrows, somehow they don't look quite right. Ah, if only you could
> build your own Barbie from scratch, right here at home.
>
> But building a model is tedious, time-consuming, error prone and
> always harder than it looks. In the world of manufacturing, where
> competition is stiff and time is money, people would like to make
> model-building a lot easier, too. The models they build are typically
> prototypes of a component or a tool, to be copied a million times in a
> mass-manufacturing operation.
>
> At a two-day workshop held on Stanford's campus in early May, industry
> representatives met with Stanford engineers and their graduate
> students to talk about new, rapid ways of designing and assembling
> physical prototypes. The underlying question: Can we now produce
> one-of-a-kind models that do more than serve as simple, show-and-tell
> displays, but that actually harbor some of the final product's
> physical characteristics smooth surfaces, resistance to heat or wear,
> mechanical strength so that they can actually perform like the
> component or tool in question?
>
> Participants discussed several methods of rapid prototype generation,
> examined models produced by various technologies and speculated on
> their possible applications well beyond the research lab or factory
> floor.
>
> Speakers even suggested that within five years a consumer version of
> rapid prototyping might help you solve the Barbie problem. It may be
> possible to download electronic directions from Mattel over the
> Internet and, using a special "3-D printer" attached to your home
> computer, construct a new plastic replica of the damaged Barbie's
> head.
>
> The workshop was organized by Stanford mechanical engineering
> Professors Friedrich B. "Fritz" Prinz and Mark R. Cutkosky and
> sponsored by the Alliance for Innovative Manufacturing at Stanford
> (AIMS). Formerly known as the Stanford Integrated Manufacturing
> Association, AIMS is a campus-based joint venture initiated by
> Stanford's Graduate School of Business and School of Engineering and
> several large corporate partners to promote the exchange of technical
> ideas between academia and industry.
>
> Layered manufacturing
>
> The workshop's primary focus was on the potential of a technique
> called layered manufacturing. In principle, any three-dimensional
> shape, no matter how complex, can be produced by decomposing its
> design into thin cross-sections, then assembling the piece by
> producing those cross- sectional layers and piling them one on the
> other.
>
> In practice, Prinz said, this can be achieved by any of a number of
> methods, each with its advantages and drawbacks. For instance, a very
> fine wire of metal or plastic can be extruded, heated to the melting
> point, and deposited according to a preset pattern over several
> iterations. An alternative method, which employs the same principle
> behind the ink-jet printers attached to many home computers, builds
> objects by targeted spraying of molten plastic layer by layer. Voids
> are filled with water-soluble wax to provide temporary support. After
> the full three-dimensional shape is produced, the supporting wax is
> removed by dissolving it with hot water.
>
> The practice of composing 3-D models in layers took root about a
> decade ago and since then has grown tenfold to more than $500 million
> in annual sales, Prinz told participants, who represented
> manufacturing sectors ranging from automobiles to primary metals,
> semiconductors and aircraft manufacturing. Recently, however, sales
> have been leveling off, he added, because these prototypes typically
> lack the physical properties of the true product, so they can't be
> used for engineering tests. As a result, the prototypes' use is
> limited to show and tell.
>
> What manufacturers need, Prinz said, is a methodology that is fast and
> extremely precise, yet yields strong, smooth-surfaced, accurately
> shaped prototypes that can actually be tested and put to work as parts
> or tools. "Our research at Stanford," he told the audience, "is geared
> at rapid prototyping techniques that allow for tremendous shape
> complexity but do not sacrifice engineering quality."
>
> Shape deposition manufacturing favored
>
> The approach favored by Prinz's group is called shape deposition
> manufacturing, or SDM. It alternates steps that add material and those
> that cut away the excesses, said Prinz, the Rodney H. Adams Professor
> in the School of Engineering.
>
> The first step is to figure out where to cut crosssections through a
> part's or tool's design. In simple thin-sectioning, all the layers are
> the same thickness. In SDM, however, the thickness of each layer
> varies, and is carefully selected in order to reproduce the shape with
> the fewest number of layers possible. After the thickness and shape of
> all the layers are determined, the object is built up by the
> successive deposition of layers of molten prototype material usually
> a wax that is not water soluble supported by a matrix of
> space-filling, water-soluble wax. After each layer is added, it is
> allowed to cool and then it is machined to achieve the precise
> geometry required. The process is repeated for each layer. When all
> the layers have been deposited and machined, the supporting matrix is
> dissolved away by immersion in water.
>
> Using SDM, Prinz said, "you can make any shape you want" in principle,
> no matter how complex. So it can reproduce extremely intricate
> engineering parts. And because it uses thicker slices than existing
> alternatives and therefore requires fewer of them SDM is faster than
> other methods, he noted.
>
> One of the current limitations of SDM, he said, is that it cannot yet
> produce quality engineering artifacts. Another problem, shared with
> other layered manufacturing techniques, is that the deposition of each
> new layer can change the properties of layers already deposited; this
> is especially true if the materials deposited are metals, whose
> crystal structure is altered by heat or exposure to other substances.
>
> For layered manufacturing to work well with metals, suitable alloys
> must be found. Several Stanford graduate students working under Prinz
> and Cutkosky discussed their research on alloys and the fine-tuning of
> deposition techniques to solve problems of shrinkage, deformation,
> lack of strength and surface roughness. Ceramics are another promising
> material type.
>
> Cutkosky, who is the Charles M. Pigott Professor of Mechanical
> Engineering, walked participants through technical details of the SDM
> design process, whereby the part or tool to be built is efficiently
> "decomposed" via various mathematical methods into the smallest number
> of layers that can accommodate its particular geometry. The ability to
> make extremely complex 3-D structures as well as to vary material
> composition gives a huge range of possible design characteristics,
> Cutkosky said. Moreover, the process is flexible enough so that
> subcomponents such as sensors or even moving pieces such as pistons
> can be embedded in the prototype at various stages of the deposition
> cycle.
>
> As you gain the capacity to embed intelligence in parts, you begin to
> produce parts that keep track of their own fatigue history (what
> stresses they've undergone, whether they're about to fail, etc.), said
> Prinz.
>
> Layered manufacturing is ideal for making "mesoscale" items whose
> dimensions are measured in the tens to hundreds of microns. Electronic
> devices in this size range bestow portability on such gadgets as
> computers, telephones, radios, watches, medical devices, and various
> sensors. Beyond that, small motors generate more power per unit of
> weight than large ones do. In theory, large arrays of tiny jet
> engines, made with shape-deposition techniques, could replace the
> giant solo engines currently mounted on airplane wings. Designers
> could build in enough redundancy say, by using 500 of these small
> engines when only 450 are actually required so that the plane still
> will fly even if 10 percent of the microengines fail, an outcome far
> preferable to the catastrophe arising from the failure of a single
> large engine.
>
> Using shape-deposition techniques, the Prinz lab has created a
> "mesicopter," a tiny flying machine made of ceramic components and
> weighing a mere 1.7 grams. In tests, the mesicopter has proven capable
> of lifting itself into the air, although it is not yet aerodynamically
> stable enough to fly without external support. The mesicopter is
> actually an array of four propellers -- each sporting fully shaped,
> 80-micron-thick blades -- occupying the four corners of a square
> plastic connecting frame and powered by a tiny commercial motor. The
> motor was acquired from a European company, said Rudy Leitgib, a
> Stanford graduate student working under Prinz's direction; but in the
> next two or three years Leitgib and his colleagues hope to have
> produced a superior, smaller micromotor of their own design.
>
>
> Rapid prototyping in automotive industry
>
> Participant Dawn White, a technical staff specialist in the
> Manufacturing Systems Department of the Ford Research Laboratory (an
> arm of Ford Motor Co.), said the era of fast prototyping already has
> arrived in the automotive industry, where, she said, even
> "experimental" processes must be able to support volumes of 50,000
> units per year or more. In this environment, she said, "pennies
> matter." Piggybacking on this, she said, is unrelenting pressure to
> reduce the product-cycle time.
>
> "Traditionally in the automotive industry, when a new model is
> designed, it's first built as a hand-built prototype for show and
> tell," White said. Conventional means take three or four months. But
> the new methods reduce this to five or six weeks. One that Ford is now
> employing, metal spray forming, operates more or less according to the
> ink-jet principle, she said.
>
> "We've been working with this technology for about five years. We can
> get up to 200,000 parts out of a tool produced this way. This may be
> enough for an entire product run of a niche product, like a new
> Thunderbird," White said. "Spray forming appears to be cheaper than
> conventional techniques."
>
> Another locale with an obvious affinity for rapid prototyping would be
> a military aircraft carrier, which might spend six months at a stretch
> out on the high seas. Spare arts could simply be produced aboard as
> needed.
>
> But the real high-impact payoff of layered manufacturing may be much
> closer to home in fact, right in the home, in the form of a 3-D
> printer that could quickly produce anything from a Star Wars toy to a
> replacement bracket for the one you just broke at 2 a.m. As
> far-fetched as this scenario may sound, White suggested that this
> capability might not be so far off.
>
> "Someday everybody will be able to print 3-D models at their desktop,"
> she said.
>
> Here's how it might work. Imagine the printer connected to your home
> computer used not only four colors of ink but, say, four colors of
> polyurethane (or some other kind of plastic) and a water-soluble wax
> to serve as a temporary space-filling support. You could go online,
> connect with the website for Hasbro or your friendly neighborhood
> hardware store, and for a small fee download a set of instructions for
> "printing" the necessity du jour. You turn on your printer, press the
> "3-D print" option and get out your nose plugs to fend off the
> olfactory assault as the "Desktop Factory" fires up. The plastic and
> wax are extruded in a skinny, fastdrying liquid jet, layer by thin
> layer, until a complex shape is built up. Stick it in a tub of water
> for a while to remove the wax, and there's your geegaw, punctual and
> pristine.
>
> White's musings were echoed by Paul Fussel, a senior technical
> specialist in product design and development at Alcoa Technology.
> Fussel suggested that the prospect of having your own 3D printer,
> capable of creating complex artifacts, is perhaps as little as five
> years off. "You'd have to get the price of one of these down below
> $500 to ignite a mass market," he said.
>
> Quite likely these 3-D printers won't appear initially in the home,
> but will first show up in a neighborhood copy shop or in the back room
> of the retail supplier itself. Said White: "Maybe this is where a
> Kinko's would come in. Or maybe it'll just be a good way for Toys 'R'
> Us to keep their inventory down."
>
>
> Other relevant sites:
>
> Stanford Rapid Prototyping Laboratory
>
> http://rpl.stanford.edu/
>
>
> Stanford Dextrous Manipulation Laboratory
>
> http://cdr.stanford.edu/html/Touch/touchpage.html
>
>
> -30-
>
> By David F. Salisbury
>
>
>
>
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