Above: Any type of image can be printed digitally with the line Globus has invented, and the pattern can be repeated exactly.

Art meets science as major steelmaker bets on digital printing technology to take coil coating to a new level

December 2019 - A team at Steel Dynamics Inc. that is already proficient with high-tech coil coating methods is making another leap by adopting digital printing.

The Fort Wayne, Indiana-based company, a producer of hot-rolled, cold-rolled and coated sheet and coil at multiple facilities, has paint lines in Butler, Indiana (300,000 tons of capacity), Jeffersonville, Indiana (190,000 tons) and Columbus, Mississippi (250,000 tons). A fourth paint line will be built at Sinton, Texas, as part of a new melt shop/rolling mill complex. Construction will begin in Texas in 2020. SDI’s painted material is consumed by such end markets as building and construction, appliance, transportation and durable goods.

This autumn, SDI contracted Globus S.r.l., Torino, Italy, to build and install a continuous digital printing coil line at Butler Works. It will be the first of its kind anywhere.

The technology developed by Globus’ president, Luigi Bagnasco, and which he named and which is marketed under the Coilor brand name, allows the user to print any digital picture—a photograph, computer-designed image or a combination of both—using Raster Image Processing (RIP) software, on a continuously running prepainted strip.

The Coilor digital printing line will be able to paint an unlimited variety of custom patterns, prints, logos and designs from a few feet long to over 30 feet. The print will be applied by a four-color digital printer, after which the coil moves through in-line UV curing equipment that’s being developed now. The printed patterns can be repeated or can be changed to another one on the fly without stopping the line and without any loss of material. After the printing is cured, a protective clear coat will be applied to protect the print and enhance its durability and life.

The line will process cold-rolled and galvanized steel coils with from 0.01-inch to 0.03-inch thick, with widths ranging from 32 to 64 inches. The maximum line speed will be 200 feet per minute.

“Ideally, SDI is interested in entering the printing market in a way that others are not involved in yet,” says Ed Traczyk, proposal and engineering manager for Double Globus Inc., the U.S. subsidiary of the Italian machinery manufacturer. “Right now they don’t have it but are being asked to do it all the time.”

“With Coilor, users can apply unlimited patterns and colors, and very long repeat patterns compared with the current technology,” explains Bagnasco.

“Our customers have been asking for us to do print coatings for some time,” says Don Switzer, sales manager at SDI’s Flat Rolled Group, Columbus Division.

Steel Dynamics will feed the digital printing line, to be installed next year, from its existing coil coating line.

Repeatability

“We are a major supplier to the garage door market. That market has transitioned from five colors to more colors and also prints, like wood grain,” explains Switzer. “They want their doors to look like wood. We hadn’t done it until now because we weren’t convinced the process was as repeatable as it needs to be.”

Currently coil coaters employ specially made print rolls that repeat patterns but, according to Switzer, “The problem with that technology is that it’s more of an art than a science. Coil coating—and everything we do because we are a steel mill—we must drive toward science and repeatability.

“We have the three newest paint lines in North America so we wanted to take an art and turn it into a science. We have been very effective with our existing paint lines. The problem was current print technology is a challenge to repeat.”

In a garage door, for example, all the sections top to bottom may not be the same size, and running coil at different times and then matching them up later is difficult, says Switzer.

He likens this to a tailor making a pinstriped suit. The stripes in the sleeves have to match up precisely to the stripes in the body of the jacket or the suit appears to be poorly made.

“With a garage door, there may be four or five sections with some being 27 inches and another 24 inches tall. The pattern on the coils may not match with existing roll printing techniques. That’s the reason we were hesitant. We wanted a technology that is highly scientific. We studied digital printing technology for years, and it was available—but not for moving strip.” With Coilor, he says, “That’s the breakthrough.”

Seamless switching

In many cases, he says, SDI is already providing the substrate for such applications. “There are a lot of those other systems, where material is run through the same line multiple times. And many companies perform that process well. A lot of people are making many prints.”

Using the Globus-built line, however, “We can put multiple prints in the same coil. Instead of having to do an entire coil with an oak wood grain, then another coil with mahogany, we now can put mahogany and oak in the same coil, and it’s just that seamless,” Switzer says. “It all a matter of computing power.”

“We are excited about that. We think there will be other applications in construction. An architect may want their building to look a certain way. You can make the surface look like brick or stone. Perhaps it could have applications in the appliance realm: Could we do a carbon steel that looks like stainless?”

Traczyk at Double Globus says the equipment will be delivered to Butler during the fourth quarter of 2020. “Then it will take several months to install and ramp up.”

Switzer is eager for the new line. “I wish the equipment would be in here faster,” he says, but acknowledges that the equipment is “very complex. It’s never been done at 64 inches wide before. We are putting up a new building for it already, next to the existing coil line. We will run steel through our paint line with a base color,” then run it through the digital printing line.

“It will be concise, repeatable and very sharp looking. This will help the steel industry and the customers,” Switzer predicts. “We will be in production mode in January of 2021.” MM