The roll covers used in soft and supercalender applications impart certain surface characteristics to the sheet and need to perform under extreme pressures.
The high loads and surface requirements of soft and supercalenders test the mettle of roll cover developmental engineers. Stowe Woodward researchers led the way to calendering performance with Superok, a superior epoxy composite cover.
Ivory and Ivory Xtreme, products of Stowe Woodward's advanced research and development, are the first commercial covers to bring the exponential benefits of nanoparticle technology to supercalender applications.
Nanoparticle covers now reach previously unattainable surfaces and wear-life when applied over steel shells, cotton rolls, on all types of calenders and even a special high-temperature formulation for Janus and Opti-load and embossing rolls.
The supercalender stack rolls give the paper a more uniform density, better smoothness and higher gloss through a series of nips created by chilled cast iron rolls mated with high modulus covered rolls.
Composite covers, some with advanced nanotechnology, achieve a more homogeneous surface for a superior surface finish and provide superior wear resistance and an exponential increase in resistance to impact damage.
Soft Calender Roll
In a soft calender, a composite-covered, variable crown roll runs against a heated metal roll to produce the desired sheet surface finish and gloss. Two reverse stacks may be used to calender both sides of the sheet.
Composite cover technology has proven to provide the best surface finish, mark resistance and "wearability" for the longest run time.
Gloss Calender Roll
The gloss calender roll presses the paper against a heated metal roll to impart high levels of gloss on heavy basis-weight coated paper and board.
Gloss calender rolls utilize rubber, polyurethane or composite covers to provide a gloss finish to the sheet while maintaining resistance to the temperature, heat age hardening and abrasion that are inherent to this application.
In calenders, it is essential to have a web free of any wrinkles to ensure high paper quality and to avoid any damages on calender rolls. Therefore, spreader rolls have to spread the web in cross direction.
To avoid paper breaks in supercalenders, the web tension has to be reduced at the edges. Simultaneously, the web should be spread. Stowe Woodward offers tripartite guide rolls (Flyroll, Take out roll) called Trioroll.
Triorolls have a special design with a very low temperature difference on the surface to avoid gloss stripes. Triorolls are maintenance free and the bearings are greased for life, meaning there is no need for regreasing and no risk of grease leaking.
Triorolls can be manufactured in steel or composite compound design. The special design TRIO-One is designed without any gaps.
Other Products and Services
Stowe Woodward Application and Service Engineers are equipped with special tools to ensure optimal sheet quality and cover performance in supercalenders, gloss calenders and soft calenders.
Advanced technologies combined with years of application expertise ensure correct nip profiles and crown calculations as well as quick turnaround from state-of-the-art mechanical roll services.