Case history: Thickness monitoring

The problem at Enhance Packaging Technologies (Whitby, ON) wasn’t so much with the thickness measuring system, but with the mismatch of measuring technology and the company’s range of film products. Enhance produces mostly LLDPE film, but the colors vary and some formulations are highly filled with EVA, explains Jim Johnson, engineering group leader. This created problems for the infrared gauge measurement system because the IR opacity of the various film products differed, and required changes to the calibration curve for each product change.

“Film thickness is one of the more important parameters for our clients, because it affects the package’s seal integrity,” says Johnson.

Two years ago, Enhance began a switch to capacitive thickness measurement systems from SolveTech Inc. (supplied in Canada by Control Solutions Inc., Brampton, ON).

“We found SolveTech’s technology is virtually immune to problems related to product changeover. There’s no significant difference in the capacitance transmittance of our various film formulations,” says Johnson.

Enhance, a subsidiary of DuPont Canada Inc., has now installed four SolveTech BF200 thickness gauges on its monolayer blown film lines. Johnson expects to purchase three more for other lines. The monitoring head is installed after the layflat, along the edge of the film. On production lines with rotating haul-offs, which is the case at Enhance, the BF200 unit allows both average and profile thickness to be measured.

In the future, Johnson is planning to experiment with on-line gauge control using the SolveTech thickness gauges. He will interface the gauges with the drive of the top nip to adjust nip speed as needed.

Jim Johnson, engineering group leader at Enhanced Packaging Technologies, says a film-thickness measurement technology from Solvetech has eliminated downtime needed for re-calibration.