The case for precision grinding linerboard machine calender rolls

Corrugated cardboard — from the boxes Amazon delivers to your door to the packaging used to protect and ship nearly every product imaginable — is made from linerboard. It’s known and judged for its durability; not for being pretty. Like a linebacker.

It’s for this reason that many linerboard manufacturers don’t consider calender roll grinds to be critical. The thinking, unfortunately, is that linerboard is driven by the strength of the paper — not by fine paper quality. So, a linerboard machine should not require precision grinds. Such grinds would be an unjustifiable waste of money.

Ironically though, it’s the opposite that’s quite true. You’re actually wasting money by not having the calender rolls on your linerboard machine precision ground. Precise, proper roll grinding is an investment in your equipment that will pay you substantial returns. Data proves it.

Let’s look at how strength variation is derived from calender roll “barring” and grind variation. Paper industry researchers (FP Innovations) have proved that short-term calender variation leads to strength variation in the lab. We here at PRG have validated these findings in our customers’ mills — saving them hundreds of thousands of dollars in the process.

Customer case study #1

• STFI variation before PRG calender grinds — 3.7
• STFI variation after PRG calender grinds — 1.7
• Caliper variation of 5-10 UM = strength variation of 20%
• 54% improvement led to BWT reduction of 35.3# to 35.1# = savings of $500,000/year

Properly ground calender rolls yield additional quality improvements and savings for linerboard manufacturers as well. Poor calender roll grinds, on the other hand, result in losses at each turn-up, which in turn yield poor winder runnability.

• Saving 250# of spool loss per reel = 1,000 tons every year = $300,000/year of savings
• Improved winder runnability = $100,000/year of savings
• Extended roll life — increased from six months to 18 months

Plus...
 

• CD Caliper 2sigma was reduced from 0.6 to 0.3
• Mullen Variation was reduced from 12.4 to 7.5
• Sheffield Smoothness was reduced from 380 to 365
• CalCoil/Air Hoses – removed
• Crowns – in control

To learn more about how our precision roll grinding can deliver improved profitability and savings to your operation, contact us today. We’ll be happy to provide you more details and validated data.