3D Printers

Material Worlds

15 Nov, 2011 By: Cyrena Respini-Irwin

3D printing is finding myriad applications — from rapid and custom manufacturing to DIY projects to parts production in space — as reliability, affordability, and functionality reach new heights.

Environmental issues. Unlike a digital prototype, which leaves behind no tangible debris, a 3D-printed model often ends up at the dump after it has served its purpose. The energy and chemicals required for various printing processes also raise concerns.

“Over time, we’re all going to have to look at environmental issues [associated with 3D printing],” said Cathy Lewis, vice-president of global marketing at 3D Systems. “For instance, today ... we offer PLA (polylactic acid) in a wide range of colors. PLA is a biodegradable thermoplastic that has been derived from renewable resources such as cornstarch and sugarcane. This makes PLA environmentally friendly and very safe to work with. The last thing we want to see is a future where we’re printing more junk, versus customized products built from biodegradable materials.”

Wohlers believes that users need to become better informed about the environmental impact of 3D printing — which includes the electricity consumed by the machine itself; the cost of shipping machines, materials, and parts to customers; and the energy used to produce raw materials — so they can make better decisions.

Plastic laser sintering, for example, requires a mix of 30% to 45% fresh material for each build. With metal sintering/melting, in contrast, almost all the material can be reused. Shochet pointed out that some polymers can be recycled to make the raw material for new prints, or ground up to create playground surfacing compounds.

On the other hand, manufacturing only the number of items needed promises waste-eliminating benefits for the environment and businesses alike. “With additive manufacturing technology, we can turn out a few of something, put it out there on the market, and if there’s sufficient demand, only then make more,” said Wohlers. “It can be the production method, or it can be used as a bridge to high-volume production.”

Matching Methods to Applications

Before selecting a method, companies must first determine that they have a legitimate need for 3D printing. It’s not appropriate for every application, such as large-volume production of end-use parts. Fischer likens the decision-making process to choosing a high-definition television: Buyers must first determine if — and how — the technology would benefit them, then decide which broad category of system would be most useful, and finally evaluate various products to find one that meets their needs.

“The technologies very much do matter, and they differ substantially,” Fischer continued. For example, FDM doesn’t offer the surface finish and level of detail required for jewelry designs, and it can’t print in full color, which is often desired for GIS applications and late-stage architectural designs. What it does provide is stable, durable, heat-resistant thermoplastic models that functionally test at 75%–80% of the strength of their injection-molded counterparts, Fischer said.

Laser-sintering machines, such as those from EOS and 3D Systems, also produce thermoplastic models that are strong enough for final products and rigorous testing. Sintering usually requires high temperatures, however, and the technology is more resistant to the ongoing slide in prices than are inkjettype methods, said Shochet.

Photopolymers, which are among the materials used by Objet and 3D Systems printers, are susceptible to warping as a result of exposure to heat, light, and humidity. “Photopolymers work well for concept modeling and prototyping a design,” said Wohlers, “but they don’t hold up over time.” He noted that such materials are also suitable for finished products that won’t be put under stress.

According to Wohlers, the costs of the various methods are “fairly comparable” at the professional level; one of the most important criteria is not price, but material properties. Does the user require a rubbery compound to test the tread on a new running shoe, or a clear plastic to observe fluid flow inside a medical device? Is the item composed of multiple materials, or is it homogeneous? Will the model undergo rigorous testing, or will it simply be passed around the room at client meetings?

To avoid disappointment, buyers should research options thoroughly and compare not only capabilities and purchase price, but the cost of ownership over time (including materials, maintenance, and electricity). Labor is also a factor: Does the machine produce support structures that will have to be cut or washed away from the printed item? Will the user need to apply a coating to strengthen or preserve the finished model? Is any sanding required to attain the desired surface finish?

Print it yourself, or order in? In addition to deciding on a method, companies must also consider a delivery model: purchase one or more machines for in-house use, send designs out for printing by a service bureau, or both? In addition to budget, the volume of items, frequency of projects, turnaround time, and security are all factors in this decision.

“When you reach a certain volume, it often makes sense to bring it in-house,” said Wohlers, but he noted that with some companies, demand frequently exceeds on-site resources, to the extent that it is actually faster to outsource. In-house printing also makes sense for sensitive designs that companies are anxious to keep under wraps. Will service bureaus be phased out as 3D printers of every type become more affordable? No, said Shochet and Fischer. They both believe 3D printing will evolve as 2D printing did, with users embracing its diverse options and using different delivery models for different applications.

David Munson created the “WTC Triptych” to show the World Trade Center site before and shortly after 9/11, as well as in its future rebuilt state (depicted here). The 17-inch-square models were 3D-printed on a Z Corporation ZPrinter and draw data from sources including 2D satellite imagery, Google Earth, photographs, publicly available 3D models, and Wikipedia. Image courtesy of Z Corporation.

Modeling the Future

The past couple of years have wrought big changes in the 3D printing industry; what can we expect in the near future? (Read the sidebar, “Zero-Gravity Tests Hint at a Galaxy of Applications.”)

Shochet has observed a consistent pattern: Technologies that are reserved for high-end machines today will be transferred to entry-level solutions tomorrow. “It’s usually three to five years from high-end to medium-range or entry pricing, but it depends on the technology. Ten years ago, if you wanted to use a clear material, you had to use a stereolithography machine that cost $300,000 to $500,000. Today, that same machine is down to $200,000, and you can print clear with an inkjet machine that costs less than $100,000 — and within a year will be less than $50,000.”

That doesn’t mean that the definition of “high-end” is static. Shochet compared the technology transfer to computing: “We had supercomputers ten years ago, that were similar in speed to what you have in your iPad now; at the same time, we have new supercomputers that are much stronger, much faster.” Likewise, printer capabilities — including material variety, versatility in colors, and material properties — are continually being expanded and enhanced. “The market is still not at the point where there is nothing left to add,” said Shochet.

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