Guide to Fabric Slitting Line Tension Rolls - FKM USA

The architecture of fabric rolls is vital and 

enduring because it brings quality; it drives 

innovation, and brings us closer to producing 

flawless metal strip. - Dr. Ulrich Freudenberg 

FKMUSA 

G u i d e to Fabric SlittinG 

line t e nSion rollS 

Examine | Understand | Improve 

FKM USA, LLC | 400 S. LaGrange Rd., Unit A | Frankfort, IL 60423 

tel. 815-469-2473 | fax. 815-469-3591 | www.fkm-usa.com


NOTES 

© 2006 FKM-USA and Industry Scope. All rights reserved. www.fkm-usa.com • www.industry-scope.com. Program designed and produced by Industry Scope. pg.

Section 1 

Roll Introduction 

Coefficient of Friction per Roll 

Type...ability to grip metal. 

Nonwoven tension rolls 

Wet or Dry CF: .3 to .35 

Flat-face polyeurethane 

tension rolls 

Dry CF: .4 to .5 

Wet CF: .1 to .2 

Pattern-cut polyeurethane 

tension rolls 

Wet CF: .2 to .25 

Pattern-cut polyeurethane 

tension rolls 

CF: Same as above 

Introduction 

The composition and construction of a 

roll, its fabric, and how it is finished are 

critical elements in understanding how 

a roll works. Knowing how a roll works 

is the first key step toward being able 

to optimize a roll in your environment.


1 

Non-woven Fabric Basics 

What is non-Woven fabric? 

A non-woven fabric is a combination of 

natural or synthetic fibers and, or mol- 

ten plastics that are entangled together 

through various processes to form a 

base or web. 

What makes a non-Woven 

fabric special? 

1. Combination of fibers and binders 

– Roll fabric is a combination of differ- 

ent kinds of fibers where the fibers may 

have varying diameters and lengths. 

This combination gives the fabric 

strength and flexibility based on the fact 

that different fibers have different prop- 

erties. The fibrous web can be further 

enhanced through the introduction of a 

polymer-binding agent that is added to 

the fabric to enhance the mechanical 

properties of the fabric. 

2. Engineered for a specific purpose 

– FKM rolls are developed and manu- 

factured by Freudenberg Nonwoven 

Group for FKM. Fabrics are specifically 

designed for FKM’s roll business. 

Section 1 – Roll Introduction 

3. Void Volume – The fabric is designed 

to have a great deal of void (or open) 

spaces. This open structure allow the 

fabric to pick up and hold dirt and fluid 

much like a sponge does, (see image 

below). As fabric is compressed onto 

a roll core some of the void, or open 

structure is compressed. Thus a roll at 

93 ShA will potentially have less open 

structure than the same fabric being 

compressed to a net hardness of only 

85 ShA. Some fabrics allow for more or 

less compression of their fibers. 

Magnification of fabric showing void volume 


How Fabric is Made 

hoW fabric is made 

To understand how non-woven fab- 

ric works, it’s important to first learn 

how it is made. There are many 

different processes and technolo- 

gies used to produce non-woven 

fabrics, but they all share three 

general steps: One, web forming; 

1. Web forming can be dry, wet, 

or spunmelt 

Two, bonding; and three, finishing. 

Forming is where individual fibers 

of various diameter and length are 

brought together and somewhat 

entangled to form a random pat- 

tern or web. Bonding is sometimes 

applied to provide specific mechani- 

cal enhancements, such as added 

2. Web bonding can be adhesive, 

thermal or mechanical (needling 

or hydroentangling) 

resiliency against cuts, tears and 

abrasions. Finishing may employ the 

use of sealers or repellents or even 

include printing or embossing. 

Adding color to the fabric does not 

change the mechanical values, it is 

simply a means of identification. 

3. Fabric finishing/treating such as 

embossing, craping, printing, 

perforating, adding chemical 

binders (like rubber) or topical 

treatments (surfactants, repellents, 

UV, FR, etc.)

oll manufacturing 

process 

The roll production process comprises 

five steps: testing and engineering, die 

cutting, pressing, finishing, and vali- 

dating and documenting. Each step is 

described below: 

1. Testing & Engineering – Pressing 

tests at our labs in Germany simulate a 

customer’s machine where we use the 

customer’s fluids and a roll covering 

that we believe will best suit the appli- 

cation. Next, a finite element analy- 

sis (FEA) study is completed on the 

customer’s roll core to determine the 

natural bending of the roll. 

FKM tests rolls to determine their 

performance in real-world condi- 

tions so that there are no unintended 

results. 


1 

How Rolls are Made 

These tests include: 

• Fluid film thickness 

• Construction and structural properties 

• Roll hardness 

• Roll finish 

• Cover durability 

• Particle pick-up 

• Operating force 

• Deflection 

• Coefficient of friction 

2. Die Cutting - A computer-controlled 

die cutter cuts separate discs from a 

sheet of non-woven fabric. 

3. Pressing – Discs are pressed onto 

the roll core using the correct loading 

procedure for the type of non-woven 

material. Pressing provides a uniform 

density and hardness of the covering 

along the length of the roll face. The 

material is then compressed onto the 

roll shaft at an approximate rate of 1:3. 

The inside diameter of the fabric disc 

is undercut to allow for an engineered 

interference fit onto the core, which 

assures a tight assembly, eliminating 

the danger of pocket formation 

Testing bench 

Die cutting of cover discs 

Pressing of discs to core 

Finishing to shape 


etween the cover and core while the 

roll is under the influence of load in a 

machine. 

4. Finishing – The roll is then turned 

and ground to the finished size and 

appropriate diameter using computer- 

controlled equipment. This allows 

FKM to achieve precise, repeatable 

results and matched sets of rolls for 

repeatable results. 

5. Validating & Documenting – After 

the roll has been completed it is 

inspected for surface finish (Ra) 

as well as for consistent hardness 

(ShA) and all aspects of the jour- 

nals and bearings (if included) are 

inspected prior to and after crating 

for shipment. A complete report 

(certification) of the roll’s condition 

at shipment is provided to the cus- 

tomer as well as specifics related to 

the roll are saved onto an RFID tag 

imbedded in the roll core for track- 

ing and future reference. 

matched sets of rolls 

During production, rolls for common 

drive systems are manufactured in 

pairs with the exact same diameter. 

This enables rolls to rotate at identi- 

cal speed, which, in helps ensure that 

rolls will perform correctly. If rolls are 

not matched, they will operate at dif- 

ferent speeds/RPMs, causing several 

problems: 

• Loose coils 

• Premature wear of the roll 

• Roll skidding 

• Part damage, including steel 

binding, tearing, wrinkling 

• Steering problems 

• Oil lines or streaks on steel 

• Uneven strip tensions 

• Premature bearing wear

At the most basic level, non- 

woven fabrics work like a sponge 

that pumps fluid off and onto the 

steel as the rolls rotate. To achieve 

optimal tension, three critical ele- 

ments of rolls work together during 

roll operation: 

1. Void volume 

2. Pressure (PLI) 

3. Roll footprint 

Each is described below. 

void volume 

Definition 


1 

How Rolls Work 

Void volume is an indication or 

measure of the amount of open 

space between the combined 

fibers and binder material web in 

a non-woven fabric. Void volume 

has a real and direct impact on the 

ability of a non-woven roll to pick 

up dirt and wring oil off of steel. 

Why Void is Important 

1. The void must be efficient at 

letting liquid in and out again. This 

means that the holes in the void 

must be the optimal size for a roll 

application. 

2. The void area allows for high 

coefficient of friction, which enables 

rolls to grip metal. Consequently, 

when the void is inadequate for 

a given application, it can fill up, 

causing the rolls to lose coefficient 

of friction and allowing the metal 

to skid or slip between trapped oil 

and the glazed surfaces of the rolls, 

thus, decreasing performance. 

3. The void impacts how long a roll 

will perform in a line—dirt loads up 

the void. The issue in this setting 

is how long a roll can perform and 

still maintain the proper character- 

istics. 

pressure (pli or 

pounds per linear inch) 

Definition 

PLI and PSI are not one in the 

same. 

PLI is used to communicate the 

amount of pressure, in pounds, 

per linear inch across the face of 

two rolls as they come together. 

PLI is a method used to calculate 

roll force; a common term that 

the roll producer, machine builder 

and end user can use to describe 

the force being exerted on and 

through the rolls. FKM tests to 

determine the optimal PLI for each 

roll application. 

Cross section of used roll 


Why PLI is Important 

• Language of PLI is carried through 

the entire process 

• Proper PLI ensures that the 

contacting points of the rolls 

create an adequate footprint. 

• Allows you to establish roll loading 

or footprint to establish the desired 

results 

• Once you establish PLI, every 

thing else follows related to proper 

machine setup 

Factors that Impact 

Roll Performance 

fluid coatings on 

incoming steel 

The thickness of the oil coating can 

vary because steel mills put different 

thicknesses of oil on the coils they 

produce. Further, if the steel has 

been in storage for a long time, the 

oil coating migrates and certain elements 

within the oil may evaporate, 

making the oil coating even more 

viscous. 

As fluid viscosity and solids increase, 

the voids in the roll fabric fill up more 

quickly, thus reducing the coefficient 

of friction.


NOTES 

© 2006 FKM-USA and Industry Scope. All rights reserved. www.fkm-usa.com • www.industry-scope.com. Program designed and produced by Industry Scope. pg. 10

Module 2 

Roll Handling, Set-up, 

and Start-up 

Introduction 

Rolls and roll covers are precisely 

engineered components that, when 

properly cared for, can be refinished 

multiple times to yield a long, useful, 

and cost-efficient life. Handling a non- 

woven roll is different than handling 

other types of steel rolls because of the 

potential for damage to the covers. In 

this section you will learn the “dos and 

don’ts” of handling rolls.

When rolls come in to FKM-USA 

for service, we often see problems 

that are a direct result of improper 

handling. Unfortunately, these 

problems can add expensive 

repairs to what may have been a 

normal maintenance routine, such 

as regrinding a roll. Typically, dam- 

age results from any or all of the 

following handling mistakes: 


2 

• Bumping the roll on the 

framework of the machine 

while removing it 

• Improperly loading the rolls 

into packing crates 

• Impressing tool marks on the 

cover while removing the roll 

from the machine 

• Damage due to weld splatter 

from storing a roll near a work 

site 

• Allowing rolls to move inside 

packing crates because rolls 

were 

not fastened in place 

• Setting the roll down on the 

floor 

Section 2 – Roll Handling, 

Set-up, and Start-up 

Problems Occurring From Improperly Handling Rolls 

• Picking a roll up with a fork lift 

in the middle rather than by 

using straps on the journals 

ends 

Properly handling rolls isn’t complicated, 

but there are several key 

guidelines you’ll need to know 

before installing or removing rolls. 

general roll handling 

guidelines 

• Always pick up and support a 

roll from the journals using 

straps to contact the journals 

• Always use a soft strap to 

touch the journals, never 

chains or other steel items 

• Never rest the roll where the 

body or cover or journals 

contacts anything 

• Leave the packing material on 

the cover until after the roll 

is installed within the machine 

• Never weld near the rolls; 

weld splatter will burn holes in 

the fabric 

• Never attempt to remove an 

end-plate from a roll. This can 

result in injury. 

Strap down assemblies 

Heal blocks to eliminate lateral 

movement during transportation 

Bubble-wrap covers 


proper handling tips 

Take care in where you touch the roll. Contact with the 

cover can cause damage that may result in undesired 

performance. Follow these general guidelines when lifting 

or setting a roll. 

• Always follow plant safety procedures. 

• Always pickup the roll from the journal ends. 

• Always use a soft strap to touch the journals. 

• Never rest the roll where the body or cover contacts 

anything— always support the roll on solid, dished blocks 

that provide clearance for the cover to stay clear of other 

objects or the floor. 

• Never rest anything against the roll where meterial comes 

into contact with the roll body or cover. 

• Leave the packing material on the cover until the roll 

is installed within the machine. 

GOOD GOOD 

BAD 

machine installation 

guidelines 

Overview 

Proper roll installation and machine 

setup are critical to optimal roll perfor- 

mance. Since each machine builder 

approaches the design of a roll stand 

in a slightly different way, we can- 

not provide specific, step-by-step 

instructions and recommend that 

you consult your machine builder for 

the proper steps to roll installation. 

We can however, provide general 

guidelines that will supplement your 

machine builder’s instructions. 

ALWAYS take the proper precautions 

to ensure that you adhere to the safe- 

ty recommendations of the machine 

builder as well as those of your plant.

introduction 

The installation of nonwoven rolls 

is critical to the performance and 

long term life cycle. Improper care 

and installation can result in the 

following operating conditions: 

• Tracking or Steering of individual 

slit strands or the entire width of 

slit section. 

• Over pressuring and or the need 

to apply excessive brake force. 

• Uneven tightness of individual 

slit coils. 

• Excessive or uneven roll cover 

ware or damage. 

pre-installation checks 

Handle Incoming Rolls 

• During uncrating, inspect for 

damage in transit 

• Keep rolls wrapped until 

installed in machine 


2 

• Ensure that rolls to be 

installed on a machine with a 

common drive are matched 

sets and are the exact 

same diameter. If the rolls 

are not matched, then do not 

install them and consult with 

FKM and/or your machine 

builder before proceeding 

Ensure Correct Bearing 

Installation 

• Install bearings using the 

appropriate tools and accoring 

to bearing makers’ specifications 

for proper journal fit, 

which can include heating the 

bearings prior to installation 

• Ensure that the bearings are 

in the correct position for 

a common fixed and float end. 

Typically, the fixed end will be 

the same as the drive end of 

the machine 

inspection and 

start-up checklist 

Review the incoming or shipped 

inspection report of new or reground 

rolls to insure the rolls are 

manufactured or service correctly. 

Inspection Items 

1. Roll cover diameters must be 

matched to within a .005” to .010” 

when a common drive is used. If 

separate drives are used for each 

roll the roll speed or RPM should 

be match within 1% variation. 

2. The roll cover concentricity or 

run out must be within .005” to 

.010” when compared to the bearing 

journals. The rolls must not 

have a taper from end to end that 

exceeds .003” to .005” 

3. The Shore “A” or Durometer 

must be within 3 to 5 points across 

each roll face to insure even tensioning. 

4. A dimensional check of the 


earing journals to insure they are 

within the bearing manufactures rec- 

ommended tolerances. 

5. Ensure that rolls are paired accord- 

ingly, particularly driven rolls 

6. Confirm that the machine is on a 

common centerline with the straight- 

ener, feeder and balance of machine 

in the line 

7. Install rolls on center, level and 

parallel to one another and the 

machine 

8. Adjust the machine to ensure the 

roll intersect is at passline 

9. Fit the keyways on drive pulleys 

At left: Ensure rolls are a matched set. 

10. Remove the packing material 

on the cover after the roll is in the 

machine 

installation into the 

tension stand 

1. The installation of rolls into the ten- 

sion stand requires attention to main- 

tain cleanliness of the roll cover sur- 

face. The accidental transfer of bear- 

ing grease, oil or dirt will cause the 

roll to improperly tension the metal. 

It is a good practice to wrap the roll 

covers with paper, plastic shrink wrap 

or bubble wrap during the installation 

process as added protection. 

2. The bearings should installed in 

compliance with bearing manufac- 

tures or machine tool builders guide 

lines and lubricated prior to installa- 

tion into the tension roll stand. 

3. Upon completion of the installation 

of the roll into the tension stand an 

alignment process must take place to 

insure the roll surfaces are parallel. 

Bottom Roll 

Most tension stands manufactures 

utilize mechanical jack screws or 

other means to adjust the bottom 

roll up or down in order to maintain 

the roll surface to the original pass 

line of the machine. This is a very 

critical part of the installation process 

and must be properly adjusted for 

re-ground rolls or new rolls. Various 

aids are used during this process that 

includes the following: Levels, Laser 

Level, Straight Edges, Gage Blocks 

or Machine Tool Builder supplied tools 

or recommendations. Upon comple- 

tion of the bottom roll installation the 

top roll installation will follow. 

Top Roll 

The top roll should be installed using 

the same process as the bottom roll 

with exception to the type of align- 

ment devices provide by the machine 

tool manufacture. In some cases 

when mechanical jack screws are 

used there is tie rod that connects

2 

the two jack screws together. A tie 

rod may or may not utilize a coupling 

that with allow each jack screw to be 

independently adjusted. The ability to 

independently adjust each end of the 

top roll will provide additional insur- 

ance that the top and bottom roll face 

are exactly parallel. 

There are several methods used to 

insure the roll faces are parallel upon 

completion of the top roll installation. 

A feeler gauge can be used along the 

roll face(s) to check the consistence of 

the gap between the rolls. Depending 

on the type slitting line and means of 

adjustment the amount of consistence 

can vary .010” to .015 across the roll 

faces. 

Upon completion of the roll installation 

it is recommended that the machine 

tool builder’s guards and electrical 

interface controls are correctly rein- 

stalled and functioning properly. 

hoW to ensure and check 

for proper roll load 

1. Adjust roll force on cylinders or jack- 

screws in accordance with roll and 

machine builder’s recommended oper- 

ating pressure 

2. Check pressure using one of the fol- 

lowing three methods: 

2.1. Place a continuous strip of 

cardboard in-between the rolls 

and bring the rolls down to ‘clamp’ 

onto the paper at the set, operating 

pressure. After about 30 seconds 

open the rolls and remove the 

cardboard. If proper, even load 

distribution is occurring, there 

will be a consistent contact 

patch image along the length of 

the cardboard. 

2.2. Insert “Stowe Foil” or 

another type of pressure-sensitive 

paper or film to check the footprint 

across the face of the roll 

2.3. Carefully (as to not damage 

the roll surface) check for gaps or 

break using a feeler gauge 

4. Vary the pressure setting, ensuring 

that the pressure is balanced from 

side-to-side, to bring the footprint into 

proper conformance with the specification. 

Note that this may vary 1-10% 

5. If after adjustments there are 

doubts, then use a load cell to take a 

direct reading at each cylinder or jackscrew 

site to ensure even pressure 

application on each end of the roll 

roll run-in 

Due to the amount of internal stress 

within a new nonwoven roll cover that 

are produced during the assembly of 

the cover onto the core it is recommended 

an initial run in procedure be 

performed. The process is simple and 

only requires rotating the rolls in jog 

control at normal operating tension 

pressure or roll force. This allows the 

rolls to redistribute the internal stress 

evenly across the entire roll face. If 

this is “not” performed and for example: 

a narrow coil is slit the roll cover 

will experience a stress relieving only 

in the area of the narrow coil width.

oll removal guidelines 

• During removal, inspect for damage. 

• Remove bearings according to 

bearing makers’ specifications using 

the proper tools (pullers). 

• Avoid bumping the roll on the frame 

work of the machine while removing 

it. 

• Ensure that exit and exit rolls are 

tagged and paired accordingly. 

• Always pick up and support a roll 

from the journals using straps to 

contact the journals. 

• Always use a soft strap to touch the 

journals, never chains or other steel 

items. 

• Never rest the roll where the body or 

At left: Proper packaging will reduce the 

potential for roll damage in transit. 

cover or journals contacts anything. 

• Never weld near the rolls; weld 

splatter will burn holes in the fabric. 

• Never attempt to remove an end-plate 

from a roll. This can result in injury. 

roll packaging guidelines 

• Ensure that the packing material, 

such as bubble-wrap, is placed 

around the cover to protect it in 

trasit. 

• Use crates or preferably steel cases 

provided by the roll manufacturer to 

ship rolls. 

• Block the rolls within the cases to 

avoid shifting. Block against the 

shoulder of the journal or end-plate 

as shown in the photo at right. 

• Use flat bed or open access ceiling 

trucks to avoid handling by fork 

trucks. 

• Block, secure and tarp the load.


NOTES 


Section 3 

Roll Operation and 

Troubleshooting 

Introduction 

Rolls and roll covers are precisely 

engineered components that, when 

properly cared for, can be refinished 

multiple times to yield a long, useful, 

and cost-efficient life. Monitoring their 

performance and recognizing prob- 

lems can further extend their life and 

improve your part quality.

overvieW 

Nonwoven tension rolls are used 

on modern slitting lines because of 

their ability to generate the highest 

degree of coefficient of friction 

or gripping action on oiled surface 

when compared to any other types 

of roll products. 

The nonwoven roll utilizes an open 

structure or porosity to achieve 

high gripping action. A simple comparison 

of the nonwoven structure 

is similar to a sponge. For these 

reasons it is critical to maintain the 

open structure of the roll surface 

to maintain the gripping action. 

The picture illustrates the nonwoven 

surface under magnification. 

Roll Build Up 

The ability to remove excess oil, 

dirt or metal particles from the roll 

surface will provide longer life and 

consistent tensioning. When the 

rolls are returned for service or 

re-grinding they are essentially cut 


3 

Section 3 – Roll Operation and 

Troubleshooting 

down to remove the excess dirt 

and oils that have loaded the surface 

voids or structure. The loading 

of the roll surface reduces the 

coefficient of friction or grip to the 

metal surface. 

In Line Maintenance 

It is recommended that rolls be 

run under normal roll force in jog 

mode to allow excess oil and dirt 

to be wrung from the roll surface 

and void areas. This will assist in 

maintaining the coefficient of friction 

and provide equal tensioning 

across the roll face. This operation 

can be performed between slitter 

head set ups or during periods of 

down time. 

This operation will also provide 

a re-leveling of the roll surface. 

Example: if a narrow coil is slit the 

entire roll face is not completely 

engaged with the metal. This will 

result in minor waves or edge 

marks in area of the metal path. 

When roll force is applied to the 

entire roll face the waves and 

edge marks will self heal to a great 

degree and provide improved tensioning 

on wider coils. 

Slitter Head Set Up 

It is recommended that the slitter 

head set up be center on the slitter 

mandrel when ever possible. 

Continuous set up to one side of 

slitter head mandrel will cause 

uneven ware on the tension rolls. 

Uneven ware will create a condition 

that will cause steering and 

tracking problems. If this condition 

is excessive the service life cycle 

is shortened and a re-grind operation 

will be required. 

Tension Stand and Roll 

Operation 

The machine tool manufacture 

provides operational instructions 

relative to the tension stand operation. 

Due to variations in tension 

designs it is recommended that 


manufactures operational instructions 

be followed. 

As general rule, the amount of roll force 

and brake force should only be enough 

to provide equal tension of each slit coil 

section. Amount of force and brake will 

vary depending on the metal gauge, 

coil width and the number of slit sections. 

Generally more force and brake 

is required on the first 5 to 10 wraps 

on the re-coiler and then the force and 

brake should be reduced to a lower 

value. 

At left: Scars from damage and wear to 

a roll after normal operation. 

Single Strip in... Multiple Strip out... 

Slitting Rolls Tension Rolls 

Look for inconsistent strip tension 

and seering issues as clues to roll 

wear indicating the need for service.


3 

troubleshooting 

Steering of Slit Strips 

Check the following points when 

you experience steering issues: 

• Improper roll installation. 

• Rolls are not parallel. 

• Uneven roll ware. 

• Over pressuring and or 

excessive brake. 

• Excessive variation of roll 

hardness across the roll face. 

• Improper grinding resulting in 

roll taper. 


mismatched diameters. 


excessive roll run out. 

• Roll surface are loaded with oil 

and dirt and require grinding. 

• Frequent slitter head set ups 

that are not centered. 

• Excess camber in the coil. 

• Slitter head set ups that place 

the coil sections to close to. non 

woven roll locking collars. 

Roll are Slipping 

Check the following points when 

you experience slipping issues: 

• Roll surfaces are loaded with 

oil, pre-lube, dirt and metal fines 

requiring a wring out procedure 

or roll re-grinding. 

• Excessive roll force, brake force 

and combination of both. 

• Excessive roll ware through the 

center section of the rolls 

causing the majority of roll force 

to be applied to the larger roll 

ends. 

• Excessive mismatch in tension 

rolls and re-coiler speed. 

• Rolls require servicing, normal 

service cycles are 6 to 12 

months based on metal type and 

operational hours. 


At left: Feeler guage shows wear 

patterns on a used roll. 

At left: Feeler 

guage shows 

condition of a 

new roll. 

At left: Check to 

ensure that end- 

plates are prop- 

erly machined 

down to avoid 

interference with 

footprint genera- 

tion while under 

load.



FKM USA, LLC | 400 S. LaGrange Rd., Unit A | Frankfort, IL 60423 

tel. 815-469-2473 | fax. 815-469-3591 

www.fkm-usa.com

Guide to Fabric Slitting Line Tension Rolls - FKM USA

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