Cutting Painted Metal is Easier, Research Shows… Um, What?

Late last month, researchers at Purdue University announced two significant discoveries re: the cutting and forming of metal. First, they discovered a previously unknown form of metal deformation, called sinuous flow, that creates microscopic folds in the metal as it is being cut. Second, they discovered relatively quick and easy a method of suppressing sinuous flow.

That’s just about the most efficient scientific research ever—“hey guys, we found this new problem and then also fixed it right away.”

Hey Hey, Ho Ho, Sinuous Flow Has Got to Go!

Using high-speed microphotography and analysis to study what happens to ductile metals when cut, the Purdue researchers found that, contrary to popular belief, metal does not necessarily shear uniformly. “When the metal is sheared during a cutting process it forms these finely spaced folds, which we were able to see for the first time only because of direct observation in real time,” said Ho Yeung, a postdoctoral research associate and member of the research team.

The brainy Boilermakers then discovered that, by simply coating the area to be cut with standard marking ink, these folding tendencies can be suppressed. Their research also discovered that adding ink at the cut allowed for a 50 percent reduction in the necessary cutting force. This leads to a 50 percent reduction in energy consumption, and allows for faster, more efficient machining.

More good news for those in the custom steel fabrication game: using less force causes less heat and vibration, which reduces wear to machine tooling and minimizes damage to the part being fabricated. This allows for greater process accuracy and, in theory, reduced part prices. Faster and cheaper manufacturing is good for everyone—if it costs less to make something, it should cost less to buy it, too, no matter what it is.

A reminder that the team did not research the effects of sinuous flow on wood or plastic.

A reminder that the team did not research the effects of sinuous flow on wood or plastic.

“The fact that the metal can be cut easily with less pressure on the tool has significant implications,” said W. Dale Compton, Purdue University’s Lillian M. Gilbreth Distinguished Professor Emeritus of Industrial Engineering and leader of the research group. “Machining efficiency is typically limited by force, so it is possible to machine at a much faster rate with the same power.”

What’s With the Ink, Do You Think?

The research team was intrigued and a little befuddled by their findings, as the marking ink was not added between the cutting tool and the cut material. Rather, it was added to the free surface of the metal and had no direct contact with the tool. One set of experiments saw the researchers applying ink to only half of the sample; once the cutting tool reached the marked section, the force required immediately dropped by half.

“It seems that the ink used commercially to mark metal is very good at suppressing sinuous flow,” said Srinivasan Chandrasekar, a Purdue professor of industrial engineering and part of the research team. “Probably because it is designed to stick well to metals.”

Research is ongoing. Funded by the National Science Foundation and conducted through Purdue’s Center for Materials Processing and Tribology, future studies will include the development of a sinuous flow model that will allow the team to better investigate the physical mechanisms at work and to study coating properties that may lead to further advances in suppression.

The team’s research paper can be found in the July 28, 2015 edition of Proceedings of the National Academy of Sciences.

Photo credit: Steve Snodgrass / Foter / CC BY

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