Almost Real: 3D printing hooks users with prototypes that bring designs to life (Cadalyst Labs Report)

Cadalyst Labs dives into the capabilities and applications of today's 3D printers.

Printing, a term generally associated with images on flat surfaces, might soon need to be redefined to include the creation of 3D shapes. In some cases, the fabrication device, or the printer, might be only slightly bigger than a standard fax machine. In other instances, you don't even have to own a machine. You can simply upload a digital model online to a 3D printing service bureau. In a matter of days, a scale model representing your idea — be it a new residential high rise, a pocket-size cell phone charger, or a custom-configured elf warrior from the World of Warcraft Online — could be on the way to your doorstep via UPS or FedEx.

This realistic prototype of a fishing reel from manufacturer Zebco is the result of parts created using an Objet Eden 3D printer and the finish work of Zebco model maker Brad Ruprecht. For more information, see the sidebar "Zebco Tackles Prototyping Tasks with Ease".

Once reserved for the creation of mockups, 3D printing has evolved into an alternative manufacturing discipline for producing parts with complex geometry in smaller volumes. At the same time, a number of technology suppliers are introducing smaller, more affordable desktop models, teasing engineers with the promise of personal prototyping machines. To help you find the right 3D printing technology and service for your business, we speak to the industry leaders, take an account of the latest models entering the market, and outline the pros and cons of certain materials and methods involved.

New Form of RP

Traditional forms of prototyping — most of which are anything but rapid — involve subtractive methods that create shapes by removing materials, such as hand sculpting, clay modeling, and laser cutting. 3D printing encompasses a new generation of rapid prototyping (RP) technologies, such as fused-deposition modeling (FDM), selective laser sintering (SLS), stereolithography (SLA), and a few others. Emerging over the past two decades with the advance of CAD, they rely on digital models as their guides and have become part of the RP lexicon. Most are considered additive fabrication because they build layers of materials to create solid models rather than cutting materials away.

Above and Beyond the Floor Plan

The definition of 3D printing, like the technologies it refers to, is still evolving. Some use it loosely to refer to all additive fabrication methods. Others prefer to limit its scope to fabrication methods derived from ink-jet printing, exemplified by the machines from Z Corp. and a few others. Terry Wohlers, the founder of Wohlers Associates and the author of Wohlers Report 2008: An in-depth global study on the advances in additive fabrication, defines 3D printing as "a less costly variation of additive fabrication (AF) technology," citing machines from Z Corp., the Dimension series from Stratasys, the PolyJet machines from Objet Geometries, and the lower-cost options from 3D Systems as examples. This article uses Wohlers' definition of the term. In the table provided here, the acronym 3DP is used to identify machines using ink-jet–based methods.

The most commonly used file format for 3D printing is STL, now an available file export option in most architectural and mechanical CAD software. In most cases, the operation to convert a CAD model to STL may be as simple as File / Save As / STL (as is the case with Autodesk Inventor, SolidWorks, Pro/ENGINEER, and Alibre Design). Some programs, such as Autodesk's Revit and 3ds Max, provide additional tools and options to parse or mesh models for the best 3D print results.

Additive Fabrication at a Glance

Applications

Because they're comparatively cheaper and faster to produce, 3D-printed prototypes have begun to replace traditional mockups in clay, wood, or foam in various industries. In architecture, 3D-printed models are used not just for design review but also for sales presentations. The ability to print embossed text strings and logos on the model's surface (a feature provided by some service bureaus such as the Colorado-based LGM allows additional branding opportunities in building models left for display at project sites. Many architectural models consist of sections and parts that are not closed volumes, or solid geometric shapes that can be printed. Architectural firms new to 3D printing should consider working with full-service 3D print shops that offer assistance to help them convert the CAD model into a 3D-printable STL file.

For civil projects, 3D printing offers a way to produce the target site's ground conditions as a scale model. To cover a large area, the user may need to print the geospatial data stored in GIS formats in smaller sections and manually assemble them into a single piece; therefore, for such projects, printers with larger build areas offer an advantage. For converting GIS files into 3D printable files, machine maker Z Corp. recommends exporting the file in VRML format.

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In mechanical and industrial design, especially in the production of consumer goods, product developers often use 3D-printed prototypes to study the design options available. More recently, because of the increased integration of finite-element analysis (FEA) software in mechanical CAD packages, it has become possible to output the color-coded analysis results using 3D printers. For these applications, machines with color printing ability should be considered.

For prototyping medical equipment, some manufacturers prefer to create transparent prototypes, even if the shipping product is designed to be manufactured in opaque materials. The transparent prototype allows engineers to examine the liquid flow inside the chambers and, if necessary, correct the geometry before mass production. This practice is especially useful for manufacturing artificial heart valves, automatic glucose delivery devices, and similar products. Manufacturers involved in producing rubber-based products, such as shoes, may prefer machines that can print models in flexible materials, as the texture and tension of the printed prototypes will better mimic the final product.

In this article

Methods

Because SLA employs photocurable resins, machines using this process tend to produce models that are slightly brittle. By contrast, the SLS machines use polymer powders, resulting in models with thermoplastic properties and surfaces with powdery texture. Many consider SLA to be a better process for producing fine, smooth parts with intricate details. But more often, SLA parts need support structures. In some rare cases, the removal of the support structure may leave behind marks that compromise the dimension of the part.

FDM uses rigid ABS plastics, producing parts similar to the thermoplastic SLS parts. Materialise, a Belgium-based prototyping firm, noted, FDM is "less appropriate for parts with living hinges," but "more appropriate for large, flat parts . . . with fewer small details," compared with the SLS process. Stratasys uses eight unique thermoplastics materials in its equipment.

Zebco Tackles Prototyping Tasks with Ease

3D printing derived from ink-jet technology uses ink-jet nozzles to create models in layers, with a liquid binder to seal them in place. The process uses a liquid agent instead of a laser, as in SLS. This method is generally considered more affordable and quicker compared with others.

Desktop Revolution

One recent advance in 3D printing involves the evolution to desktop units. Among the vendors that believe the time is right for desktop RP machines is Objet Geometries, headquartered in Rehovot, Israel. The Objet Alaris30 debuted in October 2008. It measures 32" x 34" x 41" — approximately twice the size of a typical desktop ink-jet printer — weighs 183 lb and has a build area measuring nearly 12" x 8" x 6". The machine is priced at less than $40,000.

Newcomer Desktop Factory plans a 2009 release for its 125ci 3D printer, priced at less than $5,000.

Also in October, 3D Systems announced the return of the V-Flash FTI 230 Desktop Modeler, priced at $9,900. At this price, the company hopes the machine will appeal not only to engineers and designers but also to hobbyists and students. "This affordable, easy-to-use and office-friendly 3D printer is the first product from 3D Systems based on its new Film Transfer Imaging (FTI) technology platform," the company reported. The machine is designed to operate quietly and plug into a standard electrical outlet.

The V-Flash FTI 230 re-enters the market after an April 2008 introduction led to the discovery of "several technical difficulties that affected the modeler's performance" according to the company, and sales ceased. Julie Graham, 3D Systems communications specialist, explained, "We plan to continue with carefully managed, phased rollout plans through the first quarter of 2009 and, pending the successful outcome of this phase, commence full commercial activities for the V-Flash FTI 230 Desktop Modeler in early 2009." The machine is expected to ship with Alibre Design, a familiar mid-range 3D mechanical CAD product.

Pay by Piece: The 3D Printer Service Bureau

Undercutting V-Flash's low price, Desktop Factory is planning to sell its premiere model, the 125ci, for less than $5,000 sometime this year. Although not yet available, the machine already has garnered headlines: "Printing 3D Gets Practical," hailed BusinessWeek (October 6, 2008); "Desktop Factory's Cheapo 3D Printer is Coming," reported the technology blog Engadget (www.engadget.com).

Cathy Lewis, Desktop Factory CEO, admitted, "We're not here to be best in class. We're here to bring awareness and accessibility to the market that we think has been way overpriced and way too complex for way too long."

Desktop Factory's debut machine measures a mere 25" x 20" x 20" and weighs less than 90 lb. But some sacrifices are required for its compact form factor. Its build area is only 5" x 5" x 5". Currently, it prints using only one rigid material. Color, transparent, and flexible options aren't on the menu yet.

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From Prototypes to Functional Parts

In 2005, recognizing the emerging market for printing functional parts, 3D printer developer Stratasys launched a new business unit initially called RedEye RPM and later renamed RedEye On Demand. The new division is a service bureau that produces not just prototypes but also end-use parts. The company has been asked to produce, among other things, a set of air ducts for a light aircraft manufacturer and a series of syringe storage units for a doctor.

These 3D printed parts and products are intended for daily use, not as prototypes. Joe Hiemenz, Stratasys public relations manager, pointed out, "Although rapid manufacturing (RM) is the original term, the Society of Mechanical Engineers uses the term direct digital manufacturing (DDM)" to describe this application.

From Concept to Production Mold Master in 24 Hours

For high-volume parts numbering in the thousands, traditional manufacturing methods — tooling, machining, and injection molding — remain the preferred options. But RM can produce certain parts with complex geometry, negative angles, and undercuts that present challenges for traditional methods. Because the typical turnaround time for RM is two to five days, it's ideal for making a few dozen alpha and beta units to test a product's form, fit, and function or a few hundreds parts to launch a new product while waiting for tooling setup.

In April 2006, roughly six months after its launch, RedEye On Demand began offering a flexible, rubber-like photopolymer material known as FullCure Tango. "Tango is expected to be of interest to manufacturers of products with pliable features, such as tires, toys, shoes, gaskets, keypads, overmolding, and flexible automobile trim components," announced the company.

Z Corp.'s ZPrinter 650 has five print heads that produce two to four layers per minute in full-spectrum, 24-bit color.

With the introduction of its Overnight Build service in June 2007, RedEye On Demand began providing next-day shipment for orders placed before 4 A.M. Eastern time. Several months later, in November 2007, RedEye On Demand added Ready Part, a premium service for producing parts with mold-quality smooth finishes. "The Ready Part technology also prepares models and parts for painting, plating, and postfinishing processes," according to the company.

Office and Earth Friendly

Objet Geometries describes its new Alaris30 as being "ideally suited for an office environment." Dimension, a division of Stratasys, usually describes its product line as "a fast, office-friendly, low-cost alternative."

The ubiquitous term office friendly indicates the RP machine developers' recognition that standard RP materials require careful handling. Many companies now strive — especially in designing desktop machines — to minimize or prevent user exposure to toxins and heat. They also have introduced disposable, recyclable materials.

"All current Stratasys systems use thermoplastic materials," explained Hiemenz, so printed parts can be recycled by industrial recycling firms that process plastic scrap. "Compared with subtractive manufacturing, such as machining, the additive RP process uses, for the most part, just the volume of materials needed to form the shape, so you have virtually no waste," Hiemenz added.

Joe Tiltlow, director of product management at Z Corp., said, "Beginning with the Z450, down to the latest ZPrinter 650, we use a technology that automatically recaptures the unused powder. Ninety-nine percent of that unused powder gets put back into the machine for future builds. That's a tremendous cost savings for the user. Several years ago, we used heaters to cure the parts. We realized the noise and the heat weren't suitable for office environment, so we've moved away from it. Our current technology uses heat only near the end of the build cycle."

Workhorses and Ponies

"Using additive fabrication machines to create end-use parts requires high performance, meaning larger build envelope, higher throughput, speed, accuracy, and greater material strength," explained Hiemenz. These requirements can be met only by the larger 3D printers.

"On the other end of the spectrum, there's also a trend to drive the price and footprint down for conceptual modeling," added Hiemenz. He predicts that soon 3D printing will no longer be a workgroup function but a feature available to individual design engineers, allowing them to create prototypes on the fly. If Hiemenz is correct, expect to see a divergence: the rise of larger, faster production workhorses devoted to rapid manufacturing of end-use parts and a proliferation of smaller, affordable, even personal machines for printing prototypes.

Cadalyst executive editor Kenneth Wong explores the innovative use of technology and its implications. Read his blog at www.cadalyst.com/kw. Nancy Spurling Johnson is Cadalyst's editor-in-chief.

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