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Heavy metal impact: ASU engineer improving 3-D printing of metals

New technique by ASU prof, team is a game-changer in 3-D metal printing.
September 9, 2016

As an example of an engineering breakthrough, the tiny metal arch Owen Hildreth keeps in his office at Arizona State University isn’t anywhere close to visually impressive. But it is something special once you understand how it was made.

It represents potentially game-changing progress in the emerging realms of 3-D printing and additive manufacturing — an advance that could have a dramatic impact on how things are made from metals.

Hildreth, an assistant professor of mechanical and aerospace engineering in ASU’s Ira A. Fulton Schools of Engineering, has collaborated with several colleagues to develop a technique that promises to make manufacturing of metal components, devices and structures less expensive, technically complex and labor intensive.

Significantly, the process overcomes what has been a nagging difficulty for the 3-D printing of metal objects.

Alternative to laborious machining processes

3-D printing has been a major driver of additive manufacturing. Conventional manufacturing is essentially a subtractive process. Manufacturers start with a mass of material and remove — or subtract — parts of the mass to produce a desired object.

“It’s like sculptors working with blocks of marble,” Hildreth explained. “They remove parts of the marble blocks until they get the shape of whatever kind of sculpture they wanted to create.”

Additive manufacturing, particularly with the use of 3-D printing technology, is the opposite, he said: “You just add layers of material until you get what you want. You extrude products. The printer just pushes things out in one piece.”

The process works great with lightweight and flexible plastics and polymers. But with weighty metals, it’s much more of a challenge.

That’s because when objects made of plastics and similarly “soft” materials emerge from a 3-D printer with extraneous material, the unneeded material can usually be easily cut away to give the object its intended form.

With metals, however, the high temperatures required to print them cause objects to warp as they are being printed, and so the process requires metal supports strong enough to prevent this warping. After printing, the supports must be removed to produce an object with its intended shape.

The only way to remove such supports has been through heavy-duty, laborious and painstaking machining techniques, involving the use of computer numerical control milling machines and wire electrical discharge machining.

Electrochemical etching and chemical baths

Even when 3-D printing of plastic and polymer materials does require supports, “it’s easy to make them go away,” Hildreth said. “You just break them off, or you melt them off with a soldering iron.  Or better yet, you print supports made out of a water-soluble material. You can just dunk your object in water for an hour and the support material is gone.”

That doesn’t work in printing metal objects because they require metal supports during the printing process — and metals are not water-soluble.

But here is where the new technique demonstrated in the making of Hildreth’s tiny metal arch comes into play.

Combining his expertise with that of his collaborators, they employed a printing method — called directed energy deposition — that enables the printing of an object using two kinds of metal at the same time in combination, and then electively dissolving the “sacrificial” material with a simple electrochemical etching technique.

To demonstrate their new approach, they printed the stainless steel arch supported by carbon steel.

“The stainless steel is very chemically resistant. The carbon steel is not very chemically resistant,” Hildreth said.

The printed metal structure was immersed in a “chemical bath” of nitric oxide and bubbling oxygen capable of dissolving metals that are not chemically stable — in this case, the carbon steel supporting the top of the arch.

two people in ASU lab
Arizona State University engineer Owen Hildreth (right, with ASU engineering graduate student Avinash Mamidanna) is part of a team that has developed a technique to enable more efficient and less costly manufacturing of 3-D-printed metal materials. Photo by Jessica Hochreiter/ASU

 

Combining team's wide range of expertise

“We took advantage of the differences in the chemical and electrochemical stability between the two metals,” Hildreth said. “The carbon steel was etched away without any machining. The stainless steel wasn’t affected. So what we have is the world’s first 3-D-printed metal arch made with directed energy deposition.”

What that makes possible is a big reduction in the amount of post-processing required to remove support structures from 3-D-printed metal components.

“We’re fairly certain our method is going to be applicable to a broad range of metals used in manufacturing,” Hildreth said.

To achieve the advance, Hildreth teamed up with Timothy Simpson, a professor of mechanical and nuclear engineering as well as industrial and manufacturing engineering at Pennsylvania State University, and a leading expert in both 3-D printing of metals and additive manufacturing.

They were joined by Pennsylvania State University engineering research associate Abdalla Nassar and Kevin Chasse, a corrosion engineer with the Naval Surface Warfare Center.

Together they authored the report “Dissolvable Metal Supports for 3D Direct Metal Printing” published in a recent edition of the research journal 3-D Printing and Additive Manufacturing that attracted immediate attention from manufacturing industry news outlets.

Mapping steps to further engineering advances

The team is already at work refining their techniques and mapping the next step forward. They hope to help develop methods that would apply the capabilities of 3-D printing to manufacturing metal products and structures to further eliminate the need for multiple parts and multiple assembly steps.

Along with private industry, they see the Department of Defense and NASA being particularly interested in supporting their endeavors.

They have also submitted a proposal to the National Science Foundation for support of research to look more deeply at the fundamental physics and chemistry involved in 3-D printing and additive manufacturing.

“We want to see what we can learn from mixing different materials together and printing them on top of each other,” Hildreth said. “We want to more closely study the diffusion and corrosion mechanisms involved in manipulating metals, with a focus on stainless steel, aluminum, titanium and an iron-nickel-chrome alloy.”

Local support put research on fast track

Hildreth’s recent research in these areas has been funded in large part through a Bisgrove Scholars Program award he received in 2015 from Science Foundation Arizona.

Bisgrove Scholars awards are given to academics and researchers whose work is deemed to have “the potential to transform ideas into great value for society.”

Hildreth said the support “gave me the freedom to pursue this work, which so far has led to seven patent applications and the development of two startup companies.”

 

Top photo: The making of this small metal arch involved a novel technique that promises to make it easier to produce metal objects using 3-D printing. The arch was formed by first printing a stainless steel arch supported in the center by carbon steel. After printing, the carbon steel was electrochemically removed in a mixture of nitric acid with bubbling oxygen. Since carbon steel is easily dissolved while stainless steel isn’t, this simple process leaves behind a free-standing stainless steel arch that didn’t require any of the expensive machining operations that typically plague 3-D metals printing. This process is expected to dramatically simplify 3-D metals printing. Photo courtesy of Owen Hildreth

Joe Kullman

Science writer , Ira A. Fulton Schools of Engineering

480-965-8122

 
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No internet, no power, no problem: ASU solar library empowers schools abroad

September 12, 2016

Many islands in the Pacific Ocean lack two things that are essential for accessing information and performing educational pursuits: a library and the internet.

Without this access, many teachers are without strong lesson plans or curriculum and community members lack books and multimedia.

But a new Arizona State University faculty member has figured out a way to deliver a digital library that doesn’t depend on existing internet connectivity — rather, it comes with its own Wi-Fi hotspot.

SolarSPELL,solar,ASU,education
Laura Hosman

Laura Hosman is an assistant professor who began a joint appointment in ASU’s Ira A. Fulton Schools of Engineering and the School for the Future of Innovation in Society this semester.

Her innovative device, the Solar Powered Educational Learning Library, known as SolarSPELL, is a digital library full of educational resources that generates its own Wi-Fi signal and solar power. All that is needed to access the information is an internet-capable device, such as an iPad, laptop or smartphone. Basically, it’s a self-powered plug-and-play kit, portable enough to fit into a backpack.

The plastic case containing the technical components is waterproof and weatherproof, and it is covered with a compact solar panel.

The real genius of the device lies in its small, durable, credit-card-size computer — known as a Raspberry Pi — that is used as a server and delivers the educational content over its own Wi-Fi hotspot.

“The server is one directional, so the Wi-Fi doesn’t connect to the internet, but it serves up our offline library in the form of a website, so it looks and feels as though you’re online,” Hosman explained.

Curating localized content

On the SolarSPELL website are thousands of educational resources, including videos, ranging from math and English lessons to agricultural information to overviews of climate change.

Just like a community library, SolarSPELL can be a hub for people of all ages — from young children looking to watch instructional videos to community members looking to improve their agricultural practices.

SolarSPELL's digital library connected to a smartphone.
SolarSPELL’s educational library is accessed using an internet-capable device, such as an iPad, laptop or smartphone. It operates like a self-powered plug-and-play kit. Photos by Pete Zrioka/ASU

In curating the content, Hosman insists on including as much localized information as possible. Currently, most educational content available to Pacific Islanders is provided by the governments of the U.S., Australia or New Zealand, and is not localized at all.

“When identifying content for SolarSPELL we try to think like a Pacific Islander, with a goal in the future of empowering locals to create their own unique content,” she said.

This means the device has a dual purpose of teaching things like science and geography, but also preserving and communicating local, traditional and indigenous knowledge. One example, preserved and accessible in the device, is a series of more than 70 Micronesian Seminar videos that cover 100 years of Pacific Islands history.

The importance of providing localized content came to Hosman several years ago during what she refers to as “a lightbulb moment.”

“I was showing a Micronesian Seminar video to a teacher and student, and their amazement at seeing the country’s president on the screen made me realize that these two had never actually seen a Micronesian — someone who looked like them — in a video before,” Hosman said. “It makes a huge difference if you can see yourself and your culture in the curriculum.”

Integration with Peace Corps

SolarSPELL has a strong working relationship with the U.S. Peace Corps in Vanuatu, Micronesia and Samoa. Peace Corps volunteers in the Pacific Islands are stationed at remote, rural schools for two years and have a mission to teach English and, where possible, technology in the schools.

“SolarSPELL provides a synergistic approach to the Peace Corps volunteers’ educational responsibilities, particularly when introducing technology into schools for the first time,” Hosman said.

She has learned that introducing technology in rural areas is successful only when the instructors are both technically proficient and embedded in the local community — a perfect fit for Peace Corps volunteers who know the local educational environment.

“It can take a long time to change the locals’ mind-sets and skill sets toward using technology. But Peace Corps volunteers are tech-savvy and are integrating SolarSPELL into schools in a successful way,” she said.

There are more than 100 SolarSPELL devices in the Pacific Islands, with 90 devices being managed by active Peace Corps volunteers.

A future at ASU and beyond

In January, Hosman will be taking SolarSPELL to Tonga for the first time. She is working with four engineering students in the Polytechnic School, one of the Ira A. Fulton Schools of Engineering, on curating content specific to Tonga and creating hands-on lesson plans for teaching about solar power.

With the help of ASU students, Hosman said SolarSPELL will continue to evolve and improve — from enhancing the library’s website features to identifying more cost-effective assembly methods and components to potentially coordinating a SolarSPELL build day on location in the Pacific Islands with teachers or high school students.

Hosman said the project seems to “exponentially expand” with student interest and enthusiasm. 

“What’s exciting is I don’t know what direction it will take next because ASU has an unlimited outlook and mentality,” Hosman said.

Long term, she hopes to see the device’s use expanded to all islands with Peace Corps volunteers, and then beyond.

“With time and dedication from ASU students, it could go across Africa and Asia,” she said.

Lofty aims like expanding SolarSPELL’s reach around the globe is what attracted Hosman to ASU.

“Teaching innovative concepts at a school that’s No. 1 in innovation in the country is the dream,” Hosman said.

She was attracted to the Polytechnic School for its project-based classes, especially with engineering students. 

“At many schools, engineers learn a lot of theory, but don’t get their hands busy … yet being able to tackle hands-on projects is a main reason why many of these students became engineering majors,” she explained.

Hosman has taken previous students to Haiti, Micronesia and Vanuatu. She said bringing students into the field to see their work take fruition is a life-changing experience that alters their trajectory.

“ASU supports social justice, inclusivity, hands-on teaching and multidisciplinary learning. It’s a perfect fit because that’s what I’m all about.”

A group of engineering faculty and students at a table.
Laura Hosman is working with engineering students in the Polytechnic School to introduce the device to Tonga in January 2017. From left: James Larson, electrical engineering junior; Laura Hosman, assistant professor; Bruce Baikie, engineering mentor and implementation manager/lead; Tyrine Jamella Pangan, software engineering junior; and Miles Mabey, robotics engineering junior. Photo by Pete Zrioka/ASU

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Rose Gochnour Serago

Communications Program Coordinator , Ira A. Fulton Schools of Engineering