Activity in standards development, industry initiatives and R&D are fueling the growth of additive manufacturing (3-D printing) technology in industry

The field of additive manufacturing (AM) — often referred to as three-dimensional (3-D) printing — has seen explosive growth in the past three years, and seems poised to have a profound and lasting impact on manufacturing decisions across many industry sectors. Activity in the field has been largely motivated by the technology’s potential to lower manufacturing costs, and enable revolutionary designs for a wide range of components and equipment that are simply not possible with traditional manufacturing methods. Further, a significant shift is underway in which AM technology is increasingly used for manufacturing final products for industrial use, rather than as a tool for prototyping and research and development (R&D).

However, the degree to which the well-hyped technology will infuse the industrial world in general, and the chemical process industries (CPI) in particular, depends greatly on how effectively industry stakeholders resolve a host of questions, including: How can the measurement of raw-material properties be standardized? How can the consistency and quality of final products be ensured? How will qualification and certification of final products be accomplished? How will the cost of production be managed?

Current developments in three main areas are now helping the industry address those questions and are serving to catalyze the more widespread use of AM as a commercial manufacturing method. These developments include drafting and adopting voluntary consensus standards for AM, the establishment of industry-wide consortia, and targeted R&D efforts, including the emergence of process simulation tools designed for AM.

“A confluence of factors is now coming together behind a maturing technology to accelerate the expansion of AM,” says Brent Stucker, University of Louisville (UL; www.louisville.edu) industrial engineering professor.

The expansion and maturation of AM technologies are creating opportunities for CPI companies, including the use of AM-derived components to improve the performance and efficiency of chemical processes, as well as opportunities to meet a growing demand for new raw-material formulations specifically for use in one or more of the seven distinct processes that comprise AM (see section on AM processes and materials below).

Growth and promise

The 2014 edition of the annual Wohlers Report, an AM-industry publication authored by the firm of consultant Terry Wohlers (Wohlers Associates Inc.; Fort Collins, Colo.; wohlersassociates.com), estimates that the market for 3-D printing worldwide surpassed the $3-billion mark in 2014, and saw the highest compound annual growth rate (CAGR) for the industry in 17 years, at 34.9%. From 2011 to 2013, the industry CAGR averaged 32.3%, and strong growth is expected over the next several years, Wohlers Report 2014 says.

Projections by Lloyd’s Register (London; www.lr.org) suggest the market for AM is set to grow by 390% over the next seven years.

The report further notes that growth will be fueled by sales of “personal” 3-D printers, as well as by the expanded use of the technology for producing final parts (especially metal) that go into commercial use.

Wohlers Report 2014 found that revenues from the production of parts for final products now represent 34.7% of the entire market for AM. Since 2003, this market segment has grown from less than 4% to over one-third of the total revenues from AM products and services worldwide.

AM approaches enable significant advantages over conventional formative manufacturing processes. Shane Collins, director of program management at Incodema3D (Ithaca, N.Y.; www.incodema3d.com), says key advantages include “tool-less fabrication, just-in-time inventory control, point-of-sale manufacturing, freeform fabrication, mass customization and design democratization.”

“Without doubt, AM technologies present opportunities for tighter supply chains, reduced logistics costs, more complex designs and a greater degree of customization,” adds Claire Ruggiero, technical vice president of inspection services at Lloyd’s Register Energy.

In addition to complex internal features and highly customizable parts, AM processes also have the potential to allow variable material functionality for load paths and locally altered material for wear- and corrosion-resistance. AM processes also minimize material waste and reduce the time between design and production.

“When final parts or products require a complicated geometry, and when a good method of making something is lacking, AM processes tend to be very effective and economic at delivering,” says Dave Bourell, professor of mechanical engineering and materials science at the University of Texas at Austin (UT; www.utexas.edu).

Reproducibility and materials

AM processes expose raw materials to different process physics than those in traditional manufacturing methods. And the different types of AM processes can have different raw-materials requirements. Understanding how process conditions affect the materials and the final products made from them is critical to the widespread use of AM. Questions such as “How dependent are the properties of final parts on the variables of the process?” and “How reproducible are mechanical property results?” must be addressed for AM to flourish in industrial applications.

As AM approaches are more widely used in manufacturing final products, there is increased pressure to improve process reproducibility and to expand the range of materials that can be used in the processes. UL’s Stucker sees reproducibility as a key limiting factor. “The materials that are currently available would be more widely adopted if we just had more predictability and repeatability,” he says.

“Developing new materials for AM processes requires adapting the material for the thermal history associated with that process, which is different than what you would see in conventional processes like injection molding,” explains Stucker. “Materials developed for injection molding often don’t work well for AM,” he says.

Establishing the correct process parameters for the properties of a given raw material is essential to obtaining a product with the desired properties, says John Slotwinski, a researcher at the Johns Hopkins University Applied Physics Laboratory (JHU-APL; Baltimore, Md.; www.jhuapl.edu).

“There is significant demand for the ability to use more different types of materials in AM, but so far, the leading companies have not really pushed the envelope in terms of really going after a wide range of new materials yet,” Wohlers remarks. “There’s going to be a lot of interesting activity in the area of expanding the materials, both in high-end performance materials to low-end, less expensive materials,” he predicts.

UT’s Bourell says one of the “holy grails” of AM is to have a systematic way of evaluating materials for use in AM, which doesn’t exist yet, he says.

Currently, most AM materials are developed in-house by the vendors who also sell AM machines, as a way to help ensure that the materials will work well in the process. In the future, as standards come online, materials will come from a wider variety of sources, Wohlers explains, meaning a more competitive environment in the future.

“There are many opportunities for the chemical industry to develop new polymer formulations and material chemistries that work with AM processes,” says UL’s Brent Stucker.

Cost and qualification

To fully realize the potential of AM technology, the cost of producing parts by that method will be a key parameter. “If you dissect the part cost, it turns out that the largest segment arises from the AM machine cost, followed closely by the feedstock cost,” explains UT’s Bourell, so if machines get faster and less expensive, and that is coupled with low-cost feedstock, “the markets will boom.”

However, to be able to reliably use a material in AM processing, a better understanding is required of the microstructure of a product and its degree of porosity, Bourell says.

With AM-derived products, consistency and quality control of the final parts are major concerns. “The use of final AM-made metal parts is limited primarily by the industry’s ability to certify and qualify the parts,” says JHU-APL’s Slotwinski. “The industry is still trying to figure out how to do qualification and certification quickly and easily, but it’s a tough problem.” AM’s full impact will be felt when that can be done routinely, he says.

Standardization efforts

Voluntary consensus standards represent a critical aspect of addressing the questions raised in the development of AM, and a committee at ASTM International (West Conshohocken, Pa.; www.astm.org) is working on that front. First established in 2009, ASTM Committee F42 on Additive Manufacturing Technologies now includes over 300 members from 22 countries. “We’re seeing an important wave of activity around industry standards for AM,” says Terry Wohlers, “but there’s still much work to be done.”

“Among the top industry barriers is a lack of standards,” notes Slotwinski, an F42 member who chairs the Test Methods subcommittee. “Standards help ensure correctness, confidence, consistency and common terminology.” Standardized practices, materials and techniques must be identified and validated for AM, he says.

“Currently, there is no standardized means of evidencing the safety and integrity of additive manufactured products,” says Claire Ruggiero, technical vice president for inspection services at Lloyd’s Register Energy. This is a major focus for Lloyd’s Register Energy, including participation on the British Standards Institute Committee for additive manufacturing, which is working towards generating a collection of ISO standards.

“Consensus standards programs help provide a bridge between R&D work and commercialization,” remarks Pat Picariello, ASTM director of developmental operations and staff manager of Technical Committee F42.

The efforts of ASTM Committee F42 will have a huge positive influence on the confidence of companies that want to use AM-produced parts, or those who want to enter the market as producers of raw materials, Picariello explains. “Standardization efforts have been incredibly helpful in making companies feel confident about entering the space, and using the technology,” he says.

The F42 group includes four technical subcommittees (test methods, design, materials and processes; and terminology) that have developed 10 standards to date. Another 15–20 work items are in various stages of development, with several expecting approval in 2015. ASTM is working with the International Organization for Standardization (ISO; Geneva, Switzerland; www.iso.org) to jointly develop standards for AM.

Among the approved standards the Standard Guide for Characterizing Properties of Metal Powders Used for AM Processes. The document is expected be critical for determining the properties of the feedstock powder used in AM processes — a necessary condition, ASTM says, for establishing industry’s confidence in powder selection and its ability to produce consistent components with known and predictable properties.

The standard will serve as a starting point for the future development of a suite of specific standard test methods that will address each individual property or property type that is important to the performance of metal-based AM systems and the components produced by them.

Industry initiatives

Many in the field recognize that realizing the potential of AM technology for production of engineered metallic components requires the collaboration and collective expertise of organizations involved in all aspects of the technology. And indeed, alongside the consensus standards efforts, there are also significant industry initiatives designed to foster those linkages.

Industry consortia will play a significant role in accelerating the adoption of AM, notes UL’s Stucker.

For example, the organization America Makes (Youngstown, Ohio; www.americamakes.us) is a network of over 100 U.S. government agencies, companies, academic research institutions and non-profit groups focused on AM. And the Additive Manufacturing Consortium is a group operated by engineering and technology organization EWI (Columbus, Ohio; www.ewi.org) that is designed to foster technical interchange among academia, government and industry.

Incodema3D’s Collins says industry-wide consortia will play a key role in creating the expensive material-properties databases that engineers can use to make accurate designs and that AM is currently lacking.

Meanwhile, Lloyd’s Register recently announced a new Joint Industry Project (JIP) on AM that seeks to foster collaboration among the key parties in the industry, from material and machine suppliers, manufacturers, end-users and research organizations. By collectively considering the risks and control measures from different perspectives, the JIP hopes to shape best practice standards in AM.

R&D aims

As the adoption of AM gains steam, R&D work in the field will continue to be intense. UT’s Bourell says “The AM research community needs to focus on the following areas: increase materials offerings, increase part-property reliability, reduce defects in final products, and enhance the user experience, through the development of better computer-aided design (CAD) software.”

In addition to focusing on the predictability, repeatability and reproducibility issues, and developing new materials, UL’s Stucker says that AM machine performance (speed) is an important focus of R&D, as is “learning to control material properties in the as-built and heat-treated state, and learning to overcome residual stress-induced inaccuracies.”

JHU-APL’s Slotwinski adds that developing a high-fidelity industry database of AM material properties, advancing qualification and certification protocols, and improving in-process sensing and control should be key research goals.

“In-situ process sensors and monitoring combined with closed-loop feedback will be the next step in process control capability,” Incodema3D’s Collins elaborates.

Another aspect noted by Slotwinski — developing physics-based modeling systems of AM processes — is something that UL’s Stucker is heavily involved with, and one that Stucker thinks will have a huge impact. “Accurate simulation can dramatically reduce the need for experiments,” says Stucker. “You can ‘train’ modeling software to evaluate a wide range of ‘what-if’ scenarios in AM proceses without spending as much time and resources on the experiments.”

To date, growth in AM has been based on empirical experiments, he explains, and simulations designed for the complexity and details of AM are not currently available.

Stucker started a company known as 3DSIM (Louisville, Ky.; www.3dsim.com) to commercialize modeling software and tools to fill the gap. “Simulation ability of the software we are developing can significantly increase the rate of innovation in AM,” says Stucker, because it moves the industry from an experiment-based paradigm for innovation to a simulation-based innovation paradigm.

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AM processes and materials

Additive manufacturing (AM) refers to a set of seven distinct processes for applying successive layers of a raw material in a directed fashion, according to a computer file that renders objects in three-dimensions. All AM technologies begin with 3-D models created by computer-aided design (CAD) tools. The 3-D model is converted into stereolithography format, which “slices” the model into a series of cross-sections. AM machines are considered a form of industrial robot. They use the cross-sectional slices from the computer file to lay down layer upon layer of material, eventually forming a 3-D shape that matches that of the computer file that guides it.

Conceptually, the seven different processes are similar, but important technical differences exist. The descriptions here are adapted from the ASTM F2792 Standard on AM terminology. Several of the seven main types have various subcategories.

1. Binder jetting (used with metals, plastics and ceramics). Powder material is spread over a build platform, and a liquid binder adhesive is deposited to join powder materials.
2. Directed-energy deposition (metal only). Focused thermal energy is used to fuse materials by melting as they are being deposited. The focused thermal-energy source could be a laser, electron beam or plasma arc focused to melt materials being deposited.
3. Material extrusion (polymer only). Raw material is selectively dispensed through a nozzle or orifice. Examples include fuse-deposition modeling (FDM).
4. Material jetting (polymer). Droplets of build material are jetted onto a build surface, where it solidifies. Examples include photopolymers and wax
5. Powder-bed fusion (both metal and plastic). Thermal energy (for example, a laser or electron beam) selectively fuses regions of a powder bed.
6. Sheet lamination (metal sheets, paper and plastic sheets). Sheets of raw material are bonded together to form an object. Examples include ultrasonic additive manufacturing and laminated object manufacturing.
7. Vat photopolymerization (polymer only). Liquid photopolymer resin in a vat is selectively cured by light-activated polymerization.

“Powder-bed fusion processes, like polymer laser sintering, laser-metal sintering and electron-beam melting are the leaders right now, and they have a head start on being used for direct production and manufacturing of final products,” says UL’s Brent Stucker. “Other technologies are useful for niche applications, and could move ahead rapidly, but powder-bed fusion is the sweet spot right now,” he says.

Materials used in AM are varied and include the following:

Polymers

• ABS (acrylonitrile butadiene styrene)
• PLA (polylactide), including soft PLA
• PC (polycarbonate)
• Polyamide (nylon)
• Nylon 12 (tensile strength 45 MPa)
• Glass filled nylon (12.48 Mpa)
• Epoxy resin
• Photopolymer resins

Metals

• Titanium alloy Ti6Al4V,
• Aluminum AlSi10Mg alloy
• Various types of steel (maraging steel, 15-5 PH stainless steel
• Cobalt-chromium alloy
• Inconel
• Gold and silver

Ceramic powders

• Silica/glass
• Porcelain
• Silicon carbide

Additional thoughts on Additive Manufacturing

In a recent article, Stephen Copley, director of the Center for Innovative Sintering at Penn State University (State College; www.psu.edu), wrote that “broad adoption of [AM] technology will provide an immediate impact on the suitability, affordability, and availability of critical components throughout industry, as well as enabling the exploitation of innovative designs and materials not possible using traditional manufacturing methods.”

Dan Greenfield, ATI Metals (Pittsburgh, Pa.; www.atimetals.com) says although AM is a relatively new science, its potential is huge. AM has been “gaining momentum, especially in metals, over the past 3-4 years,” Greenfield says, adding that AM has entered a transition phase in which companies are developing the ability to use it for commercial production on a larger scale than what was seen previously in earlier prototyping applications. “There are tremendous opportunities [for AM], but it’s still in the very early stages,” he says.

“AM tends to work well when companies need smaller production runs or lower numbers of products,” he adds.

“No single large technical breakthrough allowed the current fast growth of AM, but rather, it was an accumulation of many small innovations over time that eventually allowed wider use and better performance, says UL’s Stucker.

“Polymer AM is further along than metal AM, which is more complex and has more difficult technical challenges,” says John Slotwinski,. “But metal AM could be more valuable because of the high-value metal parts that can be made in that way.”

Most CPI companies have only recently started to seriously examine the technical and commercial viability of additive manufacturing, something that Lloyd’s Register says reflects the industry’s unique and challenging operating conditions and minimal risk appetite.

Scott Jenkins