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Sonoco makes crush tester for high-speed films

By: Bill Bregar

April 12, 2013

HARTSVILLE, S.C. — Sonoco Products Co. is making its radial crush tester — which measures the radial strength of paper cores for winding strength and shrink film — commercially available.

The device simulates the pressures applied during the winding processes of rolled products. Sonoco initially developed the testing instrument for its own use, since the company is the world's largest producer of the spiral-wound paperboard tubes and cores.

Now, Sonoco is offering the radial crush tester to outside companies. Customers for the testing device include film producers, distributors and end users, said Ginny Jones, Sonoco marketing associate.

Sonoco, based in Hartsville, S.C., manufacturers the tester and ships to customers. The user cuts a section of a core tube to install in the tester.

"In response to the needs of our tube and core customers, we have been committed to understanding the properties of radial crush technology for many years," said David Rhodes, director of global industrial technology. "We developed radial crush testing so we could help customers prevent failures during the winding process and optimize tube designs."

Rhodes said Sonoco still uses the testing device for its cores.

Sonoco's crush tester has approved by the Composite Can and Tube Institute as an accepted test method, the CCTI standard testing procedure T-158.

The process of high-speed winding of film — especially stretch and shrink film — can build up a huge amount of radial and retractive forces, Rhodes said. The film can lock the core onto the shaft, shutting down the winder, or the core failure can happen after the film is removed from the shaft.

In storage at the customer's facility, the temperature of the film or a high humidity environment can cause the core to fail, making that roll unusable, Rhodes said.

"As you wind up those film layers on the core, those film layers are creating a compressive force all the way along the tube. The film is squeezing the core," he said.

Big factors that influence radial force include the properties of the film, the web winding tension and the lay-on roll pressure/force.

It can cause big problems if a film manufacturer has to shut down a winder to remove a crushed film core from a shaft. "They make a lot of rolls very quickly," Rhodes said.

The tester also measures radial strength of paper cores for winding textiles, tapes and other products.