Heavy Metal Impact: Dissolving Away the Drawback

3D printing, addtive manufacturing, metals maufacturing, chemical reactions, machining techniques
The making of this small metal arch involved a novel technique that promises to make it easier to produce metal objects using 3D 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 3D metals printing. This process is expected to dramatically simplify 3D metals printing. Photo courtesy of Owen Hildreth.

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 3D 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 3D printing of metal objects.

Alternative to laborious machining processes

3D 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 explains. “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 3D printing technology, is the opposite, he says: “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 3D printer with extraneous material, the unneeded material can usually be easily cut away to give the object its intended form.

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