FINISHINGFINISHING

CALENDERINGCALENDERING

WINDING WINDING

ROLL FINISHINGROLL FINISHING

SHEET FINISHINGSHEET FINISHING

CALENDERINGCALENDERING

The paper web is pressed between The paper web is pressed between two or more rolls. two or more rolls.

The paper is molded by mechanical The paper is molded by mechanical work and plasticizing of the web.work and plasticizing of the web.

The main target : The main target : – to modify the surface structure and/or to modify the surface structure and/or

caliper of the paper to the level needed caliper of the paper to the level needed by the following processesby the following processes

CALENDERING VARIABLES CALENDERING VARIABLES

Calendering result depends on four Calendering result depends on four main factors:main factors:

- Nip pressure- Nip pressure

- Nip dwell time- Nip dwell time

- Paper plasticity- Paper plasticity

-Replications of the roll surface.-Replications of the roll surface.

The main variables are as follows:The main variables are as follows:

Paper variables affecting plasticity:Paper variables affecting plasticity:- Moisture- Moisture- Temperature- Temperature- Furnish- Furnish- Coating color formulation- Coating color formulation

Other paper variable:Other paper variable:- Formation- Formation

Calendering variables affecting plasticity:Calendering variables affecting plasticity:

- Roll temperature- Roll temperature- Steaming- Steaming

Calendering variables affecting mechanical work:Calendering variables affecting mechanical work:- Linear load- Linear load- Number of nips- Number of nips- Speed- Speed- Soft roll material (elastic modulus, Poisson factor)- Soft roll material (elastic modulus, Poisson factor)- Others (roll diameters, roll surface smoothness).- Others (roll diameters, roll surface smoothness).

CALENDER STACKCALENDER STACK

CALENDER TYPECALENDER TYPE HARD NIP CALENDERHARD NIP CALENDER

Web is pressed between two or more hard rollsWeb is pressed between two or more hard rolls

SOFT NIP CALENDERSOFT NIP CALENDER

Soft nip calender has a soft roll cover on at Soft nip calender has a soft roll cover on at least one of its two nip rolls. Most commonly, least one of its two nip rolls. Most commonly, one of the two rolls is a soft roll and the other one of the two rolls is a soft roll and the other is a heated hard roll similar to the hard nip is a heated hard roll similar to the hard nip calender heated rolls.calender heated rolls.

HARD NIP CALENDER (1)HARD NIP CALENDER (1)

Two-roll calenders are primarily used for Two-roll calenders are primarily used for calendering webs that do not need heavy calendering webs that do not need heavy calendering: for pre-calendering before calendering: for pre-calendering before coating and for finishing of uncoated coating and for finishing of uncoated woodfree papers. woodfree papers.

Multiroll calenders most commonly have Multiroll calenders most commonly have four or six rolls and are used for newsprint, four or six rolls and are used for newsprint, smooth woodfree papers, and specialty smooth woodfree papers, and specialty papers papers

HARD NIP CALENDER (2)HARD NIP CALENDER (2)

Process PrinciplesProcess Principles– densifying the web with pressure densifying the web with pressure – copying the surface of the rolls to the copying the surface of the rolls to the

web.web.

Control ParametersControl Parameters– linear pressure between the rolls linear pressure between the rolls – the roll surface temperaturethe roll surface temperature– the number of nipsthe number of nips

HARD NIP CALENDER (3)HARD NIP CALENDER (3) Advantages of hard nip calendering:Advantages of hard nip calendering:

- Cost-efficient operation- Cost-efficient operation- Effective influence on caliper profile- Effective influence on caliper profile- Simple tail threading.- Simple tail threading.

Drawbacks of hard nip calendering:Drawbacks of hard nip calendering:- Danger of blackening- Danger of blackening- Mottled surface of the web (gloss mottle and oil-- Mottled surface of the web (gloss mottle and oil-absorption differencesabsorption differences- Loss of strength- Loss of strength- Loss of bulk- Loss of bulk- Limited printing results- Limited printing results- Runnability of the process limits operating range- Runnability of the process limits operating range- Severe operational problems caused by barring and - Severe operational problems caused by barring and vibration.vibration.

Web Handling ProblemWeb Handling Problemin a hard nip calenderin a hard nip calender

SOFT NIP CALENDER (1)SOFT NIP CALENDER (1) The major difference in the nip behavior of soft calenders is The major difference in the nip behavior of soft calenders is

that both the web and the roll cover are compressing, that both the web and the roll cover are compressing, which results in a significantly lower actual pressure in the which results in a significantly lower actual pressure in the nip compared to hard nip calenders.nip compared to hard nip calenders.

The nip is longer, allowing better heat transfer and The nip is longer, allowing better heat transfer and subsequent deformation of the calendered web. subsequent deformation of the calendered web.

The compression of the web in both high and low spots is The compression of the web in both high and low spots is more evenly distributed. more evenly distributed.

The deformation of the soft cover reduces the maximum The deformation of the soft cover reduces the maximum local nip pressure resulting in more uniform calendering. local nip pressure resulting in more uniform calendering.

A hard nip calender tends to equalize the caliper of the A hard nip calender tends to equalize the caliper of the paper web resulting in small-scale density variations in the paper web resulting in small-scale density variations in the web. The soft calender tends to equalize density of the web web. The soft calender tends to equalize density of the web resulting in differences in caliper resulting in differences in caliper

HARD NIP Vs SOFT NIP (1)HARD NIP Vs SOFT NIP (1)

HARD NIP Vs SOFT NIP (2)HARD NIP Vs SOFT NIP (2)

Soft Nip CalenderSoft Nip CalenderPrinciples and Process VariablesPrinciples and Process Variables

The soft calendering process is different from the The soft calendering process is different from the hard nip calendering process in one significant hard nip calendering process in one significant way: the nip backing roll has a soft surface.way: the nip backing roll has a soft surface.

The process variables are:The process variables are:- Linear pressure- Linear pressure- Running speed- Running speed- Hot roll surface temperature- Hot roll surface temperature- Soft roll cover material- Soft roll cover material- Steaming- Steaming- Soft roll position (against top or bottom side of - Soft roll position (against top or bottom side of the web).the web).

The Benefits of Soft Nip CalenderingThe Benefits of Soft Nip Calendering

The more uniform density, the absorption The more uniform density, the absorption properties of the web and printing results properties of the web and printing results are more uniformare more uniform

As the local high spots are not compressed As the local high spots are not compressed very hard, there is less gloss mottling in very hard, there is less gloss mottling in the printed image. the printed image.

Lower maximum pressure allows the web Lower maximum pressure allows the web to be calendered to better smoothness to be calendered to better smoothness without danger of blackening. without danger of blackening.

The strength properties of the web are The strength properties of the web are maintained better compared to hard nip maintained better compared to hard nip calendering.calendering.

Soft Calender ConceptsSoft Calender Concepts Gloss calenderGloss calender

-The predecessor to today's soft calender. -The predecessor to today's soft calender. -For high basis weight board grades, formation sets limits for hard -For high basis weight board grades, formation sets limits for hard nip calendering. nip calendering.

Two-roll soft calenderTwo-roll soft calenderGloss calendering is a good process for board grades, but it cannot Gloss calendering is a good process for board grades, but it cannot be used for paper because the required pressures are higher than be used for paper because the required pressures are higher than can be tolerated by the gloss calender.can be tolerated by the gloss calender.

Three-roll soft calenderThree-roll soft calenderOne nip per side of the paper is not always enough for finishing One nip per side of the paper is not always enough for finishing the sheet.the sheet.

Four-roll soft calenderFour-roll soft calenderIt is an interesting unit for two-sided finishing It is an interesting unit for two-sided finishing

GLOSS CALENDERGLOSS CALENDER

LAYOUTS OF SOFT CALENDERSLAYOUTS OF SOFT CALENDERS

Two-Roll Soft Calender (1)Two-Roll Soft Calender (1) The main components of a two-roll soft The main components of a two-roll soft

calender are the deflection compensated calender are the deflection compensated soft covered roll and the heated roll with a soft covered roll and the heated roll with a smooth, polished surface. smooth, polished surface.

The linear pressure range of a soft The linear pressure range of a soft calender is much higher than that of a calender is much higher than that of a two-roll hard nip calender; two-roll hard nip calender;

also, the roll diameters are larger. also, the roll diameters are larger. The dimensioning linear pressure of soft The dimensioning linear pressure of soft

calender varies from 150 to 450 kN/m.calender varies from 150 to 450 kN/m. The surface temperature of the hot roll The surface temperature of the hot roll

can be up to 220°C -230°C.can be up to 220°C -230°C.

Two-Roll Soft Calender (2)Two-Roll Soft Calender (2) Threading method : open nipThreading method : open nip

Critical component : soft roll coverCritical component : soft roll cover- do not direct contact with the hot roll- do not direct contact with the hot roll- cooling the edge of the soft cover with cold air - cooling the edge of the soft cover with cold air - taper the edges of the soft roll- taper the edges of the soft roll- use edge slitters after the calender and run overwidth- use edge slitters after the calender and run overwidth- The soft covered roll wears more rapidly- The soft covered roll wears more rapidly

Other major components : Other major components : - spreader rolls before the nips- spreader rolls before the nips- paper lead rolls- paper lead rolls- steam showers- steam showers- doctors- doctors- roll edge cooling devices- roll edge cooling devices- caliper actuator- caliper actuator

WINDINGWINDING A paper web is usually stored and transferred in the form of A paper web is usually stored and transferred in the form of

rolls. This requires winding. rolls. This requires winding.

There are two basic winding processes in the paper There are two basic winding processes in the paper industry namely :industry namely :

- The - The reeling reeling process is used to produce large diameter process is used to produce large diameter rolls of paper, parent reels, for example at a paper rolls of paper, parent reels, for example at a paper machine, for further processing in the mill. Equipment used machine, for further processing in the mill. Equipment used for this process is called the reel. for this process is called the reel.

- Another winding process is called - Another winding process is called windingwinding, i.e., the term , i.e., the term "winding" means winding in general and a windup process. "winding" means winding in general and a windup process. The main function of the winding process is to produce The main function of the winding process is to produce customer rolls from parent reels. The equipment used for customer rolls from parent reels. The equipment used for winding is a winder.winding is a winder.

Three Basic Types of Winding Processes.Three Basic Types of Winding Processes.

WINDING REQUIREMENTSWINDING REQUIREMENTS The winding process can be defined as a function The winding process can be defined as a function

where a continuously manufactured or unwound where a continuously manufactured or unwound flat web is changed to a roll form for further flat web is changed to a roll form for further processing (with or without slitting)processing (with or without slitting)

General requirements for all rolls can be defined General requirements for all rolls can be defined as follows:as follows:- Correct roll dimensions- Correct roll dimensions- Round rolls and core in the center- Round rolls and core in the center- Straight roll edges - Straight roll edges - Good roll structure- Good roll structure- Clean and dust-free- Clean and dust-free- Absence of roll defects- Absence of roll defects

Internal roll tension and pressure, as well as forces during winding, can Internal roll tension and pressure, as well as forces during winding, can result in plastic deformations to the webresult in plastic deformations to the web

Machine direction (MD) plastic elongation, which Machine direction (MD) plastic elongation, which is most severe close to the core and in the is most severe close to the core and in the periphery of the roll, where positive tension periphery of the roll, where positive tension remains during roll storage, can decrease remains during roll storage, can decrease runnability in the following process.runnability in the following process.

CD variation of the MD plastic deformation, which CD variation of the MD plastic deformation, which causes bagginess and wrinkles in the following causes bagginess and wrinkles in the following process.process.

Plastic deformation in the z-direction and its Plastic deformation in the z-direction and its variation, which causes loss of caliper, bulk, and variation, which causes loss of caliper, bulk, and compressibility. The inside of the roll is affected compressibility. The inside of the roll is affected more than the periphery, where the radial more than the periphery, where the radial pressure is smallest.pressure is smallest.

Effect of Paper Properties on WindingEffect of Paper Properties on Winding

CD profile variation can be quite severe in CD profile variation can be quite severe in the winding process. Important profiles the winding process. Important profiles are:are:

- Web length profile- Web length profile- Web strain profile (MD tensile stiffness)- Web strain profile (MD tensile stiffness)- Caliper profile- Caliper profile- Compressibility profile- Compressibility profile- Moisture profile and- Moisture profile and- COF profile.- COF profile.

Effect of Winding on Paper PropertiesEffect of Winding on Paper Properties

Paper PropertiesPaper Propertiesin the radial direction from the periphery to the in the radial direction from the periphery to the

area near the spool.area near the spool.

Effect of WindingEffect of Winding

calipercaliper decreaseddecreased

stiffnessstiffness decreaseddecreased

bulkbulk decreaseddecreased

smoothnesssmoothness increasedincreased

glossgloss increasedincreased

air permeabilityair permeability decreaseddecreased

absorptionabsorption decreaseddecreased

REELINGREELING A full width sheet is wound around a reel A full width sheet is wound around a reel

spool made out of steel. spool made out of steel. The reel spool can have a cover such as The reel spool can have a cover such as

polyurethane or rubber. polyurethane or rubber. The resulting paper roll around the reel The resulting paper roll around the reel

spool is referred to as a parent reel. spool is referred to as a parent reel. It may weigh from 20 to 120 tons while the It may weigh from 20 to 120 tons while the

diameter ranges from 2 to 4 meters, 10 m diameter ranges from 2 to 4 meters, 10 m wide web, which is almost 100 kN/m as a wide web, which is almost 100 kN/m as a nip load against the spoolnip load against the spool

FUNCTIONS OF THE REELFUNCTIONS OF THE REEL

The main function of the parent reel The main function of the parent reel is to be a temporary storage unit for is to be a temporary storage unit for the paper web along different the paper web along different process steps in a production line. process steps in a production line.

A modern reel should also be able to A modern reel should also be able to perform turnup, tail threading, and perform turnup, tail threading, and grade change.grade change.

REELING PARAMETERSREELING PARAMETERS NIP LOADNIP LOAD

- Generated at the contact surface of two - Generated at the contact surface of two rolls when they are pressed together.rolls when they are pressed together.- Usually generated with either hydraulic - Usually generated with either hydraulic or pneumatic cylindersor pneumatic cylinders

WEB TENSIONWEB TENSION- The web tension is limited by the - The web tension is limited by the runnability of the web. runnability of the web. - Tension should be low enough to ensure - Tension should be low enough to ensure a minimum amount of web breaksa minimum amount of web breaks

NIP LOAD & WEB TENSION CONTROLNIP LOAD & WEB TENSION CONTROL

Stresses Inside Parent ReelStresses Inside Parent Reel

the parent reel structure has to be dense enough to disable internal movements.

In order to achieve this goal, the reel hardness must be adjustable.

REELING PHILOSOPHYREELING PHILOSOPHY

If the entire parent reel is wound too densely, the structure will become extremely rigid and internal nip stresses will increase.

For this reason, the reel structure has to be softer as the radius increases. This type of reeling philosophy is referred as "hard center structure" or "tight start"

POPE REELPOPE REEL

Reel change sequenceReel change sequence

Drum supported windingDrum supported winding

REEL PART (1)REEL PART (1)TURNUP DEVICETURNUP DEVICE

Gooseneck turnup device. Tape turnup device

REEL PART (2)REEL PART (2)PRESSING DEVICEPRESSING DEVICE

To keep the layers To keep the layers in place when in place when there is no nip there is no nip contact with the contact with the reel drum and to reel drum and to prevent air from prevent air from entering between entering between the surface layers the surface layers of the parent reel of the parent reel during the turnup during the turnup sequencesequence

REEL PART (3)REEL PART (3)Tail-threading equipmentTail-threading equipment

Tail threading to the reel is usually carried Tail threading to the reel is usually carried out with : out with : – RopesRopes– air chutesair chutes– air tubes air tubes – vacuum vacuum

In some cases, the reel drum can have a In some cases, the reel drum can have a suction zone to ensure efficient traction suction zone to ensure efficient traction between the drum surface and the tail. between the drum surface and the tail.

REEL PART (4)REEL PART (4)DriveDrive

REEL PART (5)REEL PART (5)Reel SpoolReel Spool

The diameter of the spool must be large The diameter of the spool must be large enough to support the full-width roll being enough to support the full-width roll being wound.wound.

Increasing the diameter of the spool : Increasing the diameter of the spool : – the paper mass falls on a larger area causing the paper mass falls on a larger area causing

the pressure affecting the bottom paper layers the pressure affecting the bottom paper layers to decrease considerablyto decrease considerably

– The stiffness of the spool increases, decreasing The stiffness of the spool increases, decreasing the reel interior pressures brought about by the reel interior pressures brought about by spool bendingspool bending

– the nip pressure decreases with increasing the nip pressure decreases with increasing diameter and the nip effect is gentler, diameter and the nip effect is gentler, especially at the beginning of reeling.especially at the beginning of reeling.

REEL PART (6)REEL PART (6)Frames & RailsFrames & Rails

The main purpose of the frames is to The main purpose of the frames is to support the reel equipment and the support the reel equipment and the reeling rails. reeling rails.

Most of the reeling happens with the Most of the reeling happens with the reel being supported by the rails reel being supported by the rails from the spool bearing housings. from the spool bearing housings.

REEL PART (7)REEL PART (7)Reel drum doctorReel drum doctor

to prevent the web from wrapping around the drum during a web break can be used when the web is run into the pulper or during tail threading

Another purpose for the doctor is to keep the drum surface clean.

REEL PART (8)REEL PART (8)Reels with lay-on roll for sensitive gradesReels with lay-on roll for sensitive grades

REEL PART (9)REEL PART (9) RereelerRereeler

to prepare a good and continuous parent reel for processing at the next operation.

PERKEMBANGANTEKNOLOGI REELPERKEMBANGANTEKNOLOGI REEL

ROLL FINISHINGROLL FINISHING

SHEET FINISHINGSHEET FINISHING