September 28, 2016
At the recent 15th-anniversary celebration of AICC Mexico, there was a breakout session on the movement to low basis weight packaging. It was standing room only for an audience ready to hear about this movement and what one needs to do to participate.
Containerboard
The lead-off presentation focused on the increasing supply side of linerboards and mediums, and also the proliferation of modern corrugators and flute profiles. Several mills are able to produce linerboards below 26# per MSF (125g/m2). Grades at 32# and below now represent more than 13.5 percent of all linerboard production in the United States.
While the industry has seen the conversions of uncoated freesheet, newsprint, and solid bleached sulfite machines, to make a category Test 1 linerboard sheet with 100 percent old corrugated containers (OCC) and/or mixed waste requires a greenfield mill or one that has been built from bare bones. These products, which fall into different test categories, are available, and so is the demand for the packaging that fits these newer offerings.
Europe is more than 15 years ahead of us in this respect and also in delineating their linerboards into five different quality statuses based on performance criteria. When looking at European specifications, one will soon discover additional physical property attributes such as machine direction and cross-direction tension and tear and taber stiffness. One will also learn that STFI and not cross-direction ring crush is the preferred method of testing for stacking strength potential.
Corrugating the Low Caliper Substrates
Greg Grdinich, national sales manager from BHS Corrugated–North America, spoke on their commitment to improving corrugated board, reducing washboarding, and offering new flute profiles to increase stacking strength. Grdinich also reiterated the European push into the 15–18# linerboard range, noting it will be a long time before we see that here in North America. Because short-span compressive test falls off rather abruptly below 18#, the thought is that this substance will be the line in the sand for our countries for some time.
To obtain the highest box compression test and not sacrifice edge crush and flat crush, we will expect flute heights to increase and pitch to decrease. Just the large proliferation of flute designs such as D, S, R, and T would indicate that the corrugated board pioneers are willing to take calculated risks with new board combinations and right weight constructions. In conjunction with that is the need to change the division ratio in double-wall combinations so we have more flute tip to flute tip adhesive contact points.
Converting the Combined Board
Rick Putch, director of technical services at National Steel Rule, next took the audience on a journey through the gentle converting of combined board, which is less robust and less strong than what we have used in the past. He related significant board crush to four areas in the converting process, not including feed roll crush during printing:
- Cutting die construction.
- Cutting die wear and tear.
- Machine conditions and maintenance.
- Structural design of the corrugated board itself.
Like Grdinich before him, Putch also talked about how combined board has changed the aspect ratio on double wall. He went on to talk about the changes that need to occur when die cutting hot board.
A New Way of Assuring Excellence
Randy Banks from SHARP International shared new testing and monitoring technology to assess the loss of bending or torsional stiffness from the hidden aspects of board crush. Known performance targets for specific board combinations and flutes can be compared to the actual test results. Software, which is an integral part of the testing apparatus, measures the actual retained stiffness property of the combined board after combining and after converting. Results are immediate, and corrective action can be taken on the plant floor before other combined board is compromised.
Ralph Young is the principal of Alternative Paper Solutions and is AICC’s technical adviser. Contact Ralph directly about technical that impact our industry at askralph@aiccbox.org.
