Soft Calender

Soft Calender
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The fixed crown soft calender (single nip and double nip) is suitable for calendering paper with a deckle less than 1880 mm. The internal multi-zone crown controllable roll soft calender (single nip and double nip) is suitable for calendering paper with a deckle more than 1880 mm.

Using a soft calendering machine for paper processing greatly improves the uniformity of sheet density and ensures less dots or imperfections and better printing on paper. Consequently, soft calendering machine has replaced the hard calendering machine in many paper mills.

Working Principle
Calendering is a repeating process between a smooth roll surface and a coarse web surface after the paper web comes out of the drying section. The working principle of a paper calendering machine is very similar to ironing, yielding smooth paper through the action of heat and pressure. Both the common calendering machine and the super calendering machine achieve great calendering effects through the repeated pressure of multiple rolls. The soft calendering machine accomplishes the calendering process by rising the surface temperature of rolls and the width of nip. After process is finished, the smoothness of paper can be increased by 30% to 40% while the paper thickness reduces by less than 10%.

Advantages
When pressurizing, elastic deformation of soft roll leads to surface contact between hard roll and soft roll. The surface contact width of soft calender is 10-25 mm, which is 15 times wider than that of a hard calendering machine. The unit pressure of the soft calendering machine is generally 20-40 N/mm2, which is just 1/2-1/4 of that of the hard calendering machine. Owing to the wide nip, the sheet stays longer in the nip and the energy consumption converts into heat which passes to the paper and makes the paper fiber plastify. The softened fiber is easier to be calendered, thus increasing smoothness.

The rebound resilience of surface material enables the soft roll surface to suit any bad flatness of sheet, so the soft calendering machine can achieve better softness than common hard calendering machines. Color spots can be eliminated and printability is greatly improved.

Another advantage of the soft calendering machine is paper sheet can be in motion with high moisture under the condition of elimination of paper blackening and color spots. The temperature, nip pressure, width and number of the soft calender all have impact on the calendering effect.

Main parameters

Item Index
Paper Web 1880-10000 mm
Speed 50-1000 m/Min
Linear pressure 50-300 kN/m
Temperature 180 ℃ Max.

Applications of the CCR Soft Calender
1. Standard newsprint (DIP)
2. Improved newsprint
3. SC-B rotogravure
4. LWC (Light weight coating paper) offset
5. Coated or uncoated woodfree paper
6. Coated or uncoated board
7. Print and writing paper

We are a China-based soft calendering machine manufacturer and supplier. We offer various types of products such as super soft calendering machine, hard calendering machine, friction calendering machine and two roll fabric calendering machine.

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