The owner of the North Charleston paper mill has completed a $29 million upgrade that began about 18 months ago, on time and on budget.

The investment by KapStone Paper and Packaging Corp. involved one of the three paper-making machines inside the Cooper River facility.

The replacement of the press sections and other related projects were completed on schedule earlier this month, the Northbrook, Ill.-based company said.

The investment is expected to improve the efficiency and capabilities of the so-called No. 3 machine, which KapStone said makes "ultra high-performance" grades of lightweight linerboard for manufacturers of corrugated cardboard. The company called that product "strategically important" to its business.

"The quality of the product coming off the presses appears to be outstanding off the machine," CEO Roger Stone said during a recent conference call with paper industry analysts.

The KapStone mill makes various grades of containerboard paper and specialty products that are used in flooring and laminates, such as Formica.

The No. 3 machine is newest on the factory floor, having been installed in 1957, according to an investor presentation from KapStone. It was last upgraded in 2008.

Before the improvements, the machines in North Charleston could make a combined 882,000 tons of paper products a year. When asked by an analyst, Stone declined to say specifically how much more the newly improved No. 3 can turn out.

"It will add tons to the organization," he said.

Stone added that the investment also improves the mix at KapStone's mill in Roanoke Rapids, Va., "because they will not have to run some of the products ... that will now run in Charleston."

"So, overall, it's a winning situation and exciting situation for us," Stone said. "And I am most impressed by the quality reports that I am getting today."

KapStone acquired the 77-year-old North Charleston paper mill from MeadWestvaco Corp. in 2008.