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3D Printing Myths and Methods

Engineers are intrigued by the potential of this next-generation technology.

July 1, 2014
Trans

Depending on who you listen to, 3D printing (or, as it’s more formally known, additive manufacturing) is either the biggest thing to hit the manufacturing world since the screw or the biggest tech fad since the fax machine. It’s actually a little of each.

Additive manufacturing “prints” solid objects from a digital file by depositing one layer of material on top of another, rather than starting with a piece of steel and cutting, sawing or milling it away. It allows companies to more easily manufacture complex shapes and structures that have traditionally been difficult to make. There’s also less waste compared to traditional manufacturing techniques, which require longer setup times and higher material and labor costs.

One-third (33 percent) of respondents to ASSEMBLY Magazine’s 2014 State of the Professionsurvey claim they are actively exploring additive manufacturing. That’s 7 percentage points higher than in 2013.

“We believe that 3D printing will prove a game changer for large swaths of industry and that its impact will be felt far sooner than many people expect,” says Stefan Deutscher, a principal at the Boston Consulting Group Inc. “In short, 3D printing is on a fast track to mainstream adoption—and the time for companies to weigh the ramifications for their business is now.”

However, some people question the long-term potential of the technology for high-volume parts production. They believe it will only be used for prototyping, sample production runs, making replacement parts and other niche applications.

“[The technology] does not pose a threat to traditional processes, because the materials used in 3D printing are not appropriate for the vast majority of applications,” claims Jacob Prak, CEO of Michigan Manufacturing International, which supplies assemblies, castings, stampings, machined parts, gears, bearings and other components to OEMs. “Furthermore, the cost of 3D printing techniques is at least an order of magnitude higher than traditional methods when more than a few parts are made.”

Other observers see things differently. “This is a technology which enables and inspires,” argues Richard Devon, Ph.D., a professor of engineering design at Pennsylvania State University. “You can achieve much more than you might be capable of otherwise when you have a 3D printer next to you.

 “3D printing can’t compete on price over traditional mass production,” adds Devon. “It competes on customization [and] uniqueness.”

Objects that are impossible to create with traditional machining and molding techniques can be produced with 3D printing. “[Engineers] are beginning to realize that intricate shapes can be produced that a lathe or stamping machine could not attempt,” says Devon. “It’s also theoretically possible to mix different raw materials and print fully assembled complex items with all components already in place.

“Imagine a cell phone that can be printed from a mix of materials, including plastic and metal and ceramics, complete and functional in three dimensions, with all circuit boards and even batteries included,” Devon points out. “Or, consider car dashboards with all internal components, such as wiring harnesses, dials and knobs, coming out of the printer ready to install.”

Those potential applications are still a few years away. However, engineers need to start thinking about additive manufacturing today.

“3D printing eliminates tooling costs and the time it takes to build a tool,” notes Tim Thellin, senior product manager at RedEye, the service bureau division of Stratasys Ltd. “It also gives engineers freedom to design complex geometries that would be impossible to build with traditional manufacturing technologies, improving overall part quality and performance.”

Additionally, engineers can consolidate multiple components or assemblies into one part, eliminating time and assembly costs.

“Consolidation is a key term in our industry,” says Scott McGowan, vice president of marketing at Solid Concepts Inc. “How can we make this part more lightweight, stronger and incorporate all necessary features? Additive manufacturing provides that solution.

“Consolidation means cutting down on manual labor, machining time and assembly work, which in turn means saving costs and opens the door to design more, and better,” argues McGowan. “‘Fail often,’ we say, because additive manufacturing gives you an economical way to fail fast and succeed faster.”

Dynamic Market

Additive manufacturing is more than just a fad. In fact, the technology is projected to grow by leaps and bounds during the next decade. As 3D printing speeds and material quality improve, more manufacturers will be adopting the technology.

According to the Freedonia Group Inc., the worldwide market for 3D printing equipment, materials and software will grow 21 percent per year between now and 2017, reaching $5 billion. Some of the fastest growth will be seen in the medical market, especially for dental applications such as braces, bridges, crowns and prostheses. Other big markets for 3D printing technology include automotive, aerospace, electronics and consumer products, such as jewelry and toys.

Medical device applications include custom-fit hearing aids, orthopedic implants and orthodontics that perfectly match a patient’s anatomy. “Additive manufacturing enables medical device companies to prototype and test fast, which is incredibly important in a highly regulated industry,” says Thellin. “Making improvements is as simple as updating the part’s CAD file and printing out a new part.

“In addition, medical device companies typically sell lower volumes,” Thellin points out. “If a company only produces fewer than 1,000 units, it doesn’t always make sense to invest in an injection molding tool, especially for trial runs where the risk for design changes is high.”

Aerospace and defense manufacturers have also been early adopters of 3D printing, especially for nonstructural components and replacement parts.

“The aircraft of the future will have a fuselage composed of complex parts printed using additive layer manufacturing,” claims Peter Sander, vice president of the Innovation Cell at Airbus Operations GmbH.

“From prototypes to end-use parts, aerospace has taken advantage of time and cost savings associated with additive manufacturing by producing complex geometries and combining multiple components into one part,” says Thellin. “Aerospace companies have introduced many new 3D printing applications, such as carbon-fiber layups, manufacturing tools and wind tunnel modeling.”

Process Variables

Several different additive manufacturing processes exist. And, a handful of materials can be used to print parts and subassemblies. Each option has pros and cons that engineers must carefully consider.

“While there are similarities in terms of process among different 3D printing technologies, not all printers are equally fit for the same purpose,” warns Wendy Kneissl, senior technology analyst at IDTechEx. Options include electron beam additive manufacturing, fused deposition modeling (FDM), selective laser melting (SLM), selective laser sintering, stereolithography (SLA) and ultrasonic additive manufacturing.

SLA was one of the earliest commercial methods of additive manufacturing. “[It] is one of the highest resolution approaches to 3D printing,” claims Kneissl. “As such, it is much beloved by design engineers for prototyping purposes.

“Mechanical engineers, however, prefer the FDM approach, which employs the engineering thermoplastics with which they are familiar,” adds Kneissl. FDM makes it possible for components of almost any size to be produced, because there are no predetermined space requirements to pose any restrictions.

Electron beam additive manufacturing is favored by aerospace manufacturers, such as Lockheed Martin. It is ideal for producing large-scale, near-net shape parts made of Inconel, tantalum, titanium and other high-value metals. “The process can replace a long lead-time component or unitize what was formerly many components into a single preform,” says Bob Salo, sales manager at Sciaky Inc.

With SLM, step by step laser radiation is scanned across a powder bed, which traces out the form of the component within this specific layer. Wherever the laser radiation impacts the powder, the metal powder initially melts and then solidifies to form a solid mass as the component is built-up layer by layer.

Selective laser sintering was invented in the mid-1980s at the University of Texas and commercialized in the late 1990s. “Selective sintering uses a diode-pumped fiberoptic laser that allows engineers to process higher melt-point alloys, as well as reactive alloys, such as aluminum and titanium,” says Andy Snow, senior vice president of EOS of North America Inc.

“Our process is best utilized to produce complex geometries that cannot be made by traditional manufacturing methods,” adds Snow. “This is design-driven manufacturing, as opposed to manufacturing-driven design. It gives manufacturers the ability to functionally integrate and customize products on demand.”

Ultrasonic additive manufacturing is a relatively new process, but it has big potential. It uses sound to merge layers of metal drawn from featureless foil stock. The process works with a variety of metals such as aluminum, copper, stainless steel and titanium. In combining additive and subtractive process capabilities, it can create deep slots, hollow, latticed, honeycombed internal structures and other complex geometries.

“[Between now and 2025], stereolithography and FDM approaches will continue to enjoy the majority of the share of the market, although significant growth will occur with the laser and electron beam technologies, albeit from a much smaller installed base,” predicts Kneissl.

Materials Matter

The biggest changes in the next few years will occur on the materials side. Traditionally, plastic has been the most common raw material used for 3D printing, because of cost and versatility. But, many items can now be printed in aluminum, ceramic, glass, paper, stainless steel and titanium.

“Each 3D printing technology is compatible with a different class of materials, which will have differing temperature resistance, tensile strength, elongation at break and chemical resistance,” says Kneissl. “[Engineers] need to match their application to their material, resolution and other requirements, and choose a technology accordingly. Simply choosing the cheapest printer with an adequate build-volume would likely constitute a costly mistake.

“Achieving the desired mechanical, thermal and chemical resistance properties of a 3D- printed object is a complex interplay between process parameters and feedstock material properties for any [additive manufacturing] technology,” claims Kneissl. “[Engineers] want to 3D print with the materials they are used to and want the final properties to match those possible with traditional manufacturing methods, such as plastic-injection molding. However, this is no easy task.”

Plastics such as acrylonitrile butadiene styrene (ABS), polylactic acid (PLA) and nylon were the first types of materials used in 3D printing, and remain the simplest to work with. According to the Freedonia Group, plastics will continue to account for the majority of materials demand, but faster growth is projected for metals, based on their greater strength and resistance, as well as rapid gains in markets such as aerospace.

Thanks to recent advancements in high-performance materials for FDM, such as Nylon 12 and polyetherimide, automotive engineers have started to 3D print duct work and interior parts.

“Materials have had the most incredible evolution over the past decade,” says Solid Concepts’ McGowan. “The materials available to additive manufacturing processes far exceed the PLA filaments available to the average desktop 3D printer. We print with cobalt chrome, Inconel, polyetherimide and polyether ether ketone—all incredibly durable, chemical-resistant and high-quality materials.”

“3D printers continue to get faster and more economical with an almost Moore’s Law regularity,” adds Buddy Byrum, vice president of product and channel management at 3D Systems Inc. “SLA 3D printing has doubled in speed about every 18 months over the last 10 years, approaching speeds for some parts that are nearly comparable to injection molding.

“A vast number of fab-grade materials already exist to address numerous end-use applications and new materials are being regularly released to expand capabilities,” Byrum points out. “Today, we 3D print with more than 100 different materials, ranging from food ingredients and waxes to various plastics and metals.”

Engineers are trying to figure out how to print objects from more than one material at a time. In fact, some printers are currently available that can handle more than one type of similar material at a time, such as two types of plastic. The big breakthrough will occur when there’s a machine that can print metal, plastic and other dissimilar materials.

“Most printers cannot efficiently handle multiple materials,” notes Hod Lipson, an associate professor of mechanical and aerospace engineering and computer science at Cornell University. “It’s also difficult to find mutually compatible materials. For example, conductive copper and plastic coming out of the same printer require different temperatures and curing times.

“The more dissimilar the materials are, the more exciting the design space is,” adds Lipson, who also serves as the director of the Creative Machines Lab at Cornell. “Developments will continue to be gradual. We’re going to see more and more materials available for 3D printing.” But, Lipson believes that the one-machine-that-can-do-it-all concept is still at least five years away.

Fact vs. Fiction

Unfortunately, additive manufacturing is surrounded by numerous myths and misperceptions. For instance, some tech evangelists are preaching about “the end of the assembly line.” They claim the technology will soon become as widespread as personal computers, cell phones, laptops and other devices, with consumers printing all kinds of products at home.

“People who aren’t familiar with the technology think you can fire up your 3D printer, press a button and print out a new pair of shoes in an hour,” notes RedEye’s Thellin. “That’s just not the case. First, you have to be able to design for the technology. Secondly, build time is much longer than people expect.

“Among manufacturers and engineers, expectations are unrealistic,” claims Thellin. “Our customers who haven’t worked with 3D printing often expect an injection molded-like finish from FDM technology, because it uses the same engineering-grade thermoplastics. But, since it is an additive technology, there are layer lines.” Depending on the application, some parts have to be finished and painted.

“The accuracy and tolerance are the same, but customers aren’t used to the aesthetic,” adds Thellin. “Some customers will also design 3D-printed parts the same way they would for traditional manufacturing technologies. They continue to design within the constraints of design for manufacturability rules when many of those rules don’t apply to 3D printing technology. They have more design freedom than ever before, but just aren’t aware.”

“The biggest misconception about additive manufacturing is that all 3D printers can be used for actual manufacturing applications,” says EOS’ Snow. “The term ‘additive manufacturing’ doesn’t necessarily mean that.

“There is also the belief that patent expiration is going to stimulate a tremendous amount of competition at dramatically reduced market prices,” adds Snow. “For laser-sintering technology, this simply isn’t the case. While there are groups that may want to develop their own laser-sintering technology, they don’t understand how expensive the laser alone is, never mind the platform that is built around it, in addition to quality control measures.”

As additive manufacturing moves beyond the prototyping stage, engineers are debating, “At what point does 3D printing break even with plastic-injection molding and other forms of mass production?”

“I think that’s the wrong question to ask,” says Cornell’s Lipson. “Depending on the complexity of the part, the answer is probably somewhere around 1,000 units.

“But, it’s better to ask ‘How can I take advantage of 3D printing’s ability to create a huge variety of complex parts that would not be viable using traditional mass production techniques?’ Companies that can answer that question in an interesting way can create a new business model.”

Another big misperception is that 3D printing is too slow for serious manufacturing operations. “Production-grade 3D printers are now available with large-volume print platforms (up to 1,500 millimeters) with the ability to manufacture hundreds of regular-sized items, either all the same or all unique, within a few hours,” says 3D Systems’ Byrum.

An additional myth is that part costs are higher with 3D printing vs. traditional manufacturing processes. “The key to employing 3D printing for manufacturing is to take advantage of the design freedoms and unlimited geometry freedoms inherent with 3D printing to rethink the entire product design and manufacturing strategies,” says Byrum. “It usually does not make sense to just replace a traditional manufacturing method with a 3D printer, while retaining the original product design that was developed around traditional manufacturing limitations.”

With unlimited design freedoms, new levels of product performance, with increased value and competitiveness, can be brought to market. “Numerous SKUs can be dramatically reduced allowing for more efficient and lower total cost manufacturing,” explains Byrum.

“No tooling is required, reducing the upfront fixed manufacturing investments,” Byrum points out. “And, product modifications can be made at any time without additional investments in hard tooling. In short, design complexity is free with 3D printing.”

Practical Applications

Additive manufacturing can be used to create just about any type of part or component imaginable. Some proponents have even demonstrated ways to print entire guns, automobiles and airplanes, which have attracted widespread media attention.            

But, most applications are much less glamorous and much more practical. For example, General Electric has been leading the additive manufacturing charge. It recently announced an ambitious plan to use 3D printers to produce fuel nozzles for its next-generation LEAP passenger jet engine, which will enter service in 2016.

The nozzles are expected to be lighter and stronger than those produced using conventional production techniques. GE Aviation engineers plan to print up to 19 nozzles per engine. Additive manufacturing will allow them to use a simpler design that reduces the number of brazes and welds from 25 to just five.

Rocket engine parts are also being built with similar technology. Space Exploration Technologies Corp. (SpaceX) plans to print components for its SuperDraco thruster, an engine that will power the Dragon spacecraft’s launch escape system and enable the vehicle to land propulsively on Earth with pinpoint accuracy. Inconel parts for all 18 thrusters will be created with direct metal laser sintering.

“Through 3D printing, robust and high-performing engine parts can be created at a fraction of the cost and time of traditional manufacturing methods,” claims Elon Musk, chief designer and CEO at SpaceX. “[We are] pushing the boundaries of what additive manufacturing can do in the 21st century, ultimately making our vehicles more efficient, reliable and robust than ever before.”

Additive manufacturing is typically used for more down-to-earth applications. For instance, engineers at MBX Systems, a leading manufacturer of custom server appliances and storage solutions, use the technology for prototyping new products. They have been able to shave weeks off the time previously required to create models of mechanical parts, such as battery backup mounting brackets, a motherboard input-output shield and cover plates that protect external connector ports. Most parts are printed with ABS plastic.

“We started using 3D printing [last year] because we were frustrated with the lead-time and cost of outsourcing custom-designed part prototypes,” says Jeff Luckett, director of engineering at MBX Systems. “If the fit and quality weren’t right on the first run, the cycle would start all over again until accurate, and these delays would slow down our customers’ time to market.

“The 3D printer also allows us to provide a better out-of-the-box experience for our customers, since we can send a more complete prototype, and it doesn’t arrive with a gaping hole where the custom part belongs,” Luckett points out.

“Our 3D printer saves weeks during system prototyping, due to the quick physical validation of custom parts,” adds Luckett. “For example, when part samples were fabricated in metal by outside vendors, they took three to six weeks to arrive, and reworks could take just as long. With our 3D printer, we get proof of concept more quickly and move customers into production sooner.”

There is significant cost savings, too. “Going from metal to plastic and doing the part prototyping ourselves, we’ve lowered the part cost by up to 90 percent,” claims Luckett. “What may have cost $3,000 outsourced is now $300 printed in-house. Also, by getting customers into production sooner, it’s reflected in our revenue.”

A group of Cornell University students recently 3D-printed a working loudspeaker, seamlessly integrating the plastic, conductive and magnetic parts. The device is ready for use almost as soon as it comes out of the printer.

“This simple demonstration is just the tip of the iceberg,” claims Lipson. “3D printing technology could be moving from printing passive parts toward printing active, integrated systems. Rather than assembling consumer products from parts and components, complete functioning products [will] be fabricated at once, on demand.”

Engineers at Disney Research concur with Lipson. They are experimenting with ways to print electrostatic loudspeakers that can take the shape of anything, from a rubber ducky to an abstract spiral.

The speaker technology could be used to add sound to toys, games or other consumer products. Because the same speakers that produce audible sound also can produce inaudible ultrasound, the objects can be identified and tracked so that they can be integrated into interactive systems.

“The objects can be touched or held in a user’s hand without a noticeable decrease in sound quality, so simple tactile feedback may also be possible,” says Yoshio Ishiguro, a post-doctoral associate at the lab, which is housed at Carnegie Mellon University.

The speakers are based on electrostatic speaker technology that was first developed in the early 1930s, but never widely adopted. This type of speaker is simpler than conventional electromagnetic speakers and includes no moving parts, which makes it suitable for additive manufacturing.

The simple speakers require little assembly, but even those few manual steps might be eliminated in the future. “In five to 10 years, a 3D printer capable of using conductive materials could create the entire piece,” Ishiguro predicts.

 Ishiguro and his colleagues created conductive surfaces by spraying a nickel-based conductive paint. They developed a method for making full-body compliant diaphragms using negative molds produced by 3D printing, and spraying them with the conductive paint and a polyethylene coating. Once multimaterial 3D printers are developed that can print functional electrical circuits and electrodes, these manual steps could be eliminated.  

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