Machining or molding this heptagon shape would be either impossible or prohibitively expensive. Instead, it was produced via rapid manufacturing, the emerging technology that shows promise for low-volume, complex parts. Impossible shapes? How about this chair, inspired by a Mobius strip? EOS worked with Siavash Mahdavi at University College London and world-renowned designer Assa Ashuash to create Osteon. The chair was RM’ed in plastic on EOS equipment, and the design was driven by Mahdavi’s artificial intelligence software. 3D Systems recently introduced a new material called Accura55, an ABS-like resin designed to increase productivity with its low viscosity and substantially reduced postprocessing and finishing requirements. The company says that this material also provides engineers and designers with strong, functional models featuring fine detail and smooth surface finish. An example of RM’s efficiency for low volumes, shown here, is the ability to nest smaller parts together to produce an entire production run in one pass. Burton received an award from 3D Systems in 2004 for its snowboard bindings. Prototypes produced via SLA equipment were field-tested daily until Burton’s designers felt they had optimized the binding. These are examples of products that could be made via RM for low-volume, niche markets. New materials are bringing better properties to RM parts. For example, DSM Somos recently introduced DMX100 with an impact strength up to 0.80 J/cm, a flexural modulus ranging from 2000-2400 MPa, and the stiffness of standard ABS with more than twice the impact strength, along with up to 20% elongation at break. Custom shapes for implants are more easily and quickly rendered in RM. This implant, made in an EOS direct metal laser sintering unit, was created in days. Traditional manufacturing requires weeks. RM can also refer to parts used in manufacturing other products, such as the assembly jig shown here and used by BMW to fabricate automobiles. When Klock Werks Kustom Cycles, which builds one-of-a-kind motorcycles, entered Discovery Channel’s Biker Build-Off, it had 10 days to build a custom bike that would go on to win the top award at a national show. Its engineers worked with Stratasys to RM all plastic parts in five days from polycarbonate, including the gauge pod, fork tube covers, headlight bezel, floorboard mounts, floorboard undercovers, and wheel spacer cover. All parts withstood speed testing at 147 mph, and cost about 75% less to produce than comparable IM parts.

Advances in rapid manufacturing lie beneath the technology’s promising status as the best answer for low-volume, complex-geometry parts. But the experts agree: It is no replacement for injection molding.

Rapid manufacturing has been called many things—from a disruptive technology and Star Trek wannabe to brand-specific labels such as e-manufacturing (EOS), direct digital manufacturing (Stratasys and the Society of Manufacturing Engineers), and even instant manufacturing (3D Systems). But no matter what the moniker, this emerging technology shouldn’t be ignored or feared by the molding industry. For one thing, it’s not just for military and aerospace parts any more.

In fact, applications in production today range from knee implants in stainless steel to low-volume camera housings in ABS. And for those who see RM as a threat to injection molding, industry expert and consultant Todd Grimm (T.A. Grimm & Assoc. Inc., Edgewood, KY) confirms this is hardly the case. “Rapid manufacturing can’t compete with injection molding, and no one is predicting it will. For one, it makes sense only in low volumes—less than 1000 in general—and is only viable when the part has some degree of complexity.”

Perhaps a dose of RM is just what the doctor ordered for molders who want to broaden portfolios, add value, and offer alternatives to both established and potential customers. Further, the wide variety of service bureaus in the United States makes this technology one that can be sampled without risk. Initial jobs can be outsourced to test the waters without a heavy investment in equipment. Interested yet?

From the ground up

Let’s define the process of RM before going any further, because it is subject to a degree of misconception. This is neither rapid prototyping nor rapid tooling. It is an additive fabrication method that uses digital data to create a physical object for series production or to be used in production, according to sources that range from Wikipedia to the Society of Manufacturing Engineers’ Rapid Technologies & Additive Manufacturing community. Further, additive fabrication refers to methods such as fusion, sintering, and polymerization of materials.

Generally speaking, a part that is RM’ed is built the same way as a rapid prototype or rapid tool, with one of the additive processes such as stereolithography, fused deposition, or laser sintering. With most additive techniques, a layer of powdered or liquefied material is deposited on a building platform and then “cured” by laser, light, electron beam, or other means to form a solid. Each layer is defined by the part’s CAD file, which is sliced up into thin horizontal cross sections and stored as an STL file that additive equipment can process. Layers are built up and cured until the part is complete. Materials from polymers to metals can be used.

Of the rapid technologies now available, RM is currently ranked number one as far as growth predictions are concerned. Industry consultant and analyst Terry Wohlers of Wohlers Assoc. (Fort Collins, CO) contends that RM will become the single largest application of additive fabrication in the future, eclipsing the other two major rapid categories—design models and fit-and-function prototypes. “Every year, we survey service providers and system manufacturers and ask them, based on their interaction with customers, how are the systems being used? In 2003, 3.9% of their customers’ business was RM, but early in 2007, that number rose to 11.7%,” Wohlers says (see graph, p. 34). “It is now a significant piece of the pie, and future growth trendlines are expected to continue rising at a similar pace.”

What makes an application a good candidate for RM? Most industry pundits agree that there are several requirements:

• Geometric features are complex. This can be anything from an impossible-to-machine or -mold shape to those that conform to the body.
• Traditional methods are expensive. Forging, investment casting, diecasting, injection molding, and the direct machining of these shapes requires time, secondary processes, and/or expensive tooling.
• Volumes are low. Niche markets, mass customization, and specialty products are the environments in which RM makes sense from a cost perspective.
• There is a need for speed. For industries such as aerospace and motorsports, where OEMs may need only 100 parts but they need them quickly for repair or replacement, having products on demand is a major plus.
Time to market is another recurring theme in the RM story. “Medical implant manufacturers have begun to look at laser sintering as a more cost-effective way to make products,” adds Wohlers. “The traditional lead time to create a hip replacement is six to eight weeks after the tooling is available. It takes three weeks just to get the surface rough enough so the bone will attach to it, because they have to send it out for a special sintering process. With RM, the surface can be programmed to be built as rough and porous.”

When, why, and how?

Answers are generally mixed when rapid technology gurus are asked how soon RM is likely to become a significant force in the world of manufacturing. “Not in our lifetime,” “Perhaps as early as 10 years from now,” and “There are few clear indicators” are examples of the current thinking. Most agree, however, that it is not a question of if, but a matter of when.

These experts also agree on the answers to why. Cost is one. RM eliminates several steps from the process of either molding plastic parts or creating metal ones, especially the need to create a mold, tool, or die. Aside from the expense involved in making them, molds and dies are time-consuming to produce (with rare exceptions). Compare the two weeks it may take for a rapidly machined mold or mold insert to the 20 hours needed to make the part itself via RM. Finally, the “riches in niches” are best served by a technology that’s fast and cost-effective at low volumes.

The answer to how can be found among the major additive system vendors—Arcam, 3D Systems, EOS, and Stratasys. These equipment makers offer models and material choices for RM, including (but not limited to):

• EBM (Arcam): Titanium, Ti alloys, and other metals
• HiQ (3D Systems): PA, glass-filled PA, metals, elastomers
• Eosint P-Class (EOS): PA, glass-filled PA, carbon-fiber PA, aluminum-filled PA, flame-retardant PA, polystyrene, metals
• FDM (Stratasys): ABS, PC, PPSU, polymer blends

Accuracy and layer depth are the two factors most critical in RM applications. As layers get thinner, surface finish improves. While no one has achieved a Class A surface with RM equipment, the push to improve surface quality is on. One of the first manufacturers to adopt laser sintering for making production metal parts, Morris Technologies Inc. (MTI; Cincinnati, OH), is able to produce layers as thin as 20 µm (0.0008 inch) and feature details down to 0.203 mm (0.008 inch).

Reality check

In 2003, MTI was the first company in North America to acquire DMLS (direct metal laser sintering) equipment offered by EOS. Today, MTI produces direct parts for a variety of applications and industries including aerospace, automotive, medical, electronics, and others. Greg Morris, principal and COO, tells IMM that he believes this niche of producing complex metal parts via laser sintering will be revolutionary.

“In very niche markets like aerospace and medical, there can be a significant time savings to produce parts over traditional manufacturing methods, plus economies of scale when producing hundreds of parts,” Morris says. “We’re at the very beginning of what this technology can do, and I believe it will still be growing and maturing 20 years from now. The future for certain applications and geometries will clearly be in additive fabrication. As materials, machines, and tolerances improve, the potential for these services will be in the billions of dollars. It does not take a huge stretch of imagination to foresee this technology continuing to evolve and advance over the next five to 10 years. During that period of time, people will get smarter about it. Any company looking at rapid technologies will see many compelling reasons to get involved.”

Grimm also believes in the growth of RM, but says it is best not to overhype this technology, especially for moldmakers and custom and captive molders. “Direct digital manufacturing offers these groups an outlet to augment their business, but it will be a couple of years before this movement gains steam.”

Wohlers disagrees. Already, he is seeing it pick up steam, not only in the United States, but also in Europe and other parts of the world, such as South Africa. “New types of products are being designed and manufactured that before were impossible or impractical due to cost,” states Wohlers. He cites examples such as custom jewelry, dental restorations, lighting designs for businesses and homes, collectables such as action figures, awards and corporate gifts, custom parts for commercial business jets, and high-end infrared cameras.

The equipment manufacturers are headed toward thinner layers, according to Grimm, but the thinner the layers are, the more time it takes to build a part. “Even at half a thousandth in layer thickness, you can’t reach a Class A surface. We’ll need another order of magnitude below that to mimic molded parts. And there are other caveats. With RM, machines have more variability. I could have two of the same machines from the same manufacturer and still have slight variations between the parts. It’s not unlike the beginning of the IM industry.”

But forward-looking manufacturers aren’t waiting around for features that match injection molding, says Stratasys’s product marketing manager, Fred Fischer. “They are taking advantage of the technology for competitive advantage. In a statistically sound 2006 survey of Stratasys customers, a surprising 42% of FDM users said they are already using their machines for at least some rapid manufacturing. And more than 30% of our RedEye service bureau jobs are now rapid manufacturing jobs.”

When asked to summarize the benefits of RM, Fischer adds an idea that designers may find intriguing. “In addition to its other many positive aspects, RM enables great design freedom. For instance, you can change a design without penalty in under an hour by making a small change to a CAD file. Contrast this to the weeks or months it can take to rework a tool. Also, RM eliminates design-for-manufacturing constraints because even impossible geometries are possible.”

Contact information Arcam AB | +46 (31) 710 32 00 | www.arcam.com EOS | (248) 306-0143 | www.eos.info T.A. Grimm & Assoc. Inc. | (859) 331-5340 | www.tagrimm.com Morris Technologies Inc. | (513) 733-1611 | www.morristech.com Society of Manufacturing Engineers | (313) 425-3000 | www.sme.org Stratasys Inc. | (952) 937-3000 | www.stratasys.com 3D Systems Corp. | (803) 326-4080 | www.3dsystems.com Wohlers Assoc. | (970) 225-0086 | www.wohlersassociates.com