An Embedded Sensing System for Paperboard Tubes
Research by
Huldah Gronvall/ Prof. Lawrence Bank
Dept of Civil & Environmental Engineering

Over the past few decades, due to increased speeds and capacities of manufacturing equipment, there has been a steady increase in the performance requirements for spirally-wound paperboard tubes (also known as "cores") on which paper, film, metals, and textiles are wound.

Paperboard tubes are usually made from recycled paperboard materials like cardboard boxes and office paper. Such paperboard tubes range in size from diameters as small as 1 inch to as large as 36 inches with tube-wall thicknesses from as little as 0.1 inches to 1.0 inch. The mechanical and physical properties of paperboard tubes have significant influence on numerous production variables including speed of the winding operation, amount of material that can be wound on the tube, and long-term stability of the material on the tube. The moisture content (MC) in particular is a key physical property that influences many mechanical properties of a core.

Professor Bank's Composite Structures Research Group at the University of Wisconsin-Madison is working with Sonoco Products Company, the world's largest manufacturer of paperboard tubes, to develop new embedded sensing technologies for these tubes. The objective of this research is to develop a method that provides a fast, accurate, non-destructive, and perhaps contact-less way of measuring the MC in these cores. Presently, the most accurate way to measure the MC of paperboard is by calculating the difference between a sample's "original" weight and that of its "dried" weight. By this method, the weight difference between the "wet" and "dry" condition is used to calculate the moisture content as follows:

Necessary to this method, however, is that a sample has to be drawn from the paperboard. In other words, a piece of the core has to be destructively removed to use for the oven-drying. A prevailing objective of the current project is to develop a non-destructive method to measure MC. This objective is presently being explored through strain-gauging cores and finding a relationship between mechanical strain and MC.

Strain-Gauged Tube

Presently, Sonoco is examining ways to develop an inventory-control system for paperboard tubes using Radio Frequency Identification (RFID) Tags. The contact-less aspect of this research involves interfacing a MC sensor with this inventory system so that the MC of these tubes can be read at any point in storage, shipment, and/or distribution. The principal, guiding objective is that such a system would supplant today's rudimentary methodologies which are currently characterized by destructive and/or inaccurate MC-measuring techniques including oven-drying and moisture meters that use electrical resistance to measure MC. Non-destructive, remote techniques for measuring tube properties, such as those being developed through these joint efforts, would be of great interest - and value - to the industry.

RFID Tag

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