The Art of Owning & Operating Rubber Calenders

Rubber & Tyre 

Knowledge On-The-Go Special Supplement 

Machinery 

http://rubbermachineryworld.com / http://tyremachineryworld.com 

World 

The Art of Owning 

and Operating Rubber 

CALENDERS 

Also 

Inside 

7 Proven Strategies To Methodically Grow Your Business

Contents 


Machinery 

http://rubbermachineryworld.com / http://tyremachineryworld.com 

Knowledge On-The-Go Special Supplement 

World 

July 2016 

8COVER STORY 

The Art of Owning 

and Operating 

Rubber Calenders 

A cover story that you will like for all the right 

reasons as it covers the different facets of 

rubber calenders. 

5 

37 

INSIGHT 

7 Proven Strategies To Methodically 

Grow Your Business 

RUBBER&TYREMACHINERYWORLD 

INFORMATIONONEQUIPMENT,TECHNOLOGY,INNOVATION&SUPPLIERS 

KNOWLEDGE-ON-THE-GO 

Through A Gadget Of Your Choice 

 

INFORMATION PORTAL | E-MAGAZINES | INTERVIEWS | KNOWLEDGE PARTNERS | DOWNLOADS 

........... And More

| Editor’s Note | 

The Art of Owning & Operating Rubber 

Calenders 

Calendering is one of the oldest rubber processing 

technologies. This is a mechanical process by which rubber 

is pressed into textiles (cloth, fabric, tire cord) forming 

composite sheets. 

Rubber Calendering is classified into two based on what you 

are calendering. Your guiding principle for calender line 

operation should be consistency and continuity. 

The machinery that helps you do rubber calendering is 

known as a Rubber Calender and it performs various 

functions. This is a heavy-duty machinery consisting of 

two or more rolls that revolve in opposite directions. 

Today, you have a wide range of new and used calender 

purchase options. 

Choosing the right Rubber Calender is important; learning 

to operate it smartly is equally key for your success with 

this machine. This edition covers all these aspects in a 

descriptive manner. 

In addition, we have the ‘Insight’ section that is an 

infographic on ‘7 Proven Strategies To Methodically Grow 

Your Business’. I hope you enjoy this issue. 

Choosing the right 

Rubber Calender 

is important; 

learning to operate 

it smartly is equally 

key for your 

success with this 

machine. 

7 

As always, I welcome your feedback on 

rubbermachineryworld@gmail.com. 

Best Regards 

Prasanth Warrier 

rubbermachineri 

rubbermachineryworld 

+Rubbermachineryworld1 

grp/home?gid=8252803 

rubbermachineri 

(Disclaimer: The pictures and statements in our special supplements are shared by the respective companies and/or sources mentioned. 

Rubber & Tyre Machinery World does not verify/vouch for their genuineness, hence will not be liable for any misrepresented data) 

Rubber & Tyre Machinery World | JUL 2016

| CALENDERS | 

8 

Image: Rodolfo Comerio 

The Art of Owning and Operating 

Rubber Calenders 

Prasanth Warrier 

Calendering is one of the oldest rubber 

processing technologies. This is a 

mechanical process by which rubber is 

pressed into textiles (cloth, fabric, tire 

cord) forming composite sheets. 

The machinery that helps you do rubber 

calendering is known as a Rubber 

Calender. The word 'calender' itself is a 

derivation of the word kylindros – the 

Greek word that is also the source of the 

word 'cylinder'. 

Despite its development in 1836, 

calendering as a process became 

popular only after the 1930's 

(almost 200 years later)! 


| CALENDERS | 

Delayed rise to popularity 

In 1836 Edwin M. Chaffee, of the Roxbury 

India Rubber Company, patented a fourroll 

calender to make rubber sheet. He 

worked with Charles Goodyear with the 

intention to 'produce a sheet of rubber 

laminated to a fabric base'. 

Despite this development, calendering as a 

process became popular only after the 

1930's because it was difficult to adjust the 

desired gap between rolls. Consequently, it 

was difficult to get an accurate rubber 

sheet thickness. 

Since the calender machines became easier 

to adjust, features have evolved. Modern 

calenders' can achieve tolerances around 

±0.005mm and their lines are adaptive for 

most sophisticated precision requirements 

of your product. 

Purpose of Rubber Calendering 

In calendering process, you pass pre-selected 

fabric and rubber through a series of rolls to 

flatten, smoothen and sandwich the 

materials. 

- On the other hand, a 'supported' sheet has 

textile fabric or steel cord coated with a 

film of rubber (also known as 'skim stock 

rubber') on both sides and into the material. 

Supported rubber sheets give you higher 

strength or tear resistance. 

The adhesion of rubber to the fabric or steel 

cord is critical to final performance. And the 

rubber compound that you coat the fabric is 

different from the one used to make the 

tread or that which coats the cords. 

Coating of fabrics has been done for almost 

200 years. Steel cord and fabric cord topping 

is a process in your tire manufacturing. 

Specifications and tolerances for calendered 

cords are tough. So you will find it difficult 

to fulfill the thickness variation across the 

calendered ply and the cord density. 

For example, you use calendared textiles for 

casing, cap plies and chafers in tyre industry. 

And you use calendered steel cord for belts. 

Calendering process is also well adopted in 

plastic industry (say, PVC sheeting). 

Image: JM Machinery 

9 

Depending on your end-use, the calendered 

sheets could have multiple layers 

'sandwiched' together. 

A Rubber Calender can help you get either 

'supported' or 'unsupported' calendered 

sheets. 

- Unsupported' sheets contain only layers of 

rubber that has been joined together. 


| CALENDERS | 

Image: Maxxis Canada 

10 

Types of Rubber Calendering 

Rubber Calendering is classified based on 

what you are calendering, (A) Fabric 

calendering and (B) Steel cord calendering. 

Each of these is different yet similar in 

operations and sensitive to environment 

influence for your high quality product. 

This textile is arranged in a flat and parallel 

manner. Under proper tension they are 

continually pressed through two rolls. 

Simultaneously, you add the rubber 

compound to the opening area or nip 

between the rolls. As a result, a thin layer of 

rubber is applied into top of and the bottom 

layers of the fabric. 

A. Fabric Calendering 

The materials that go into your fabric 

calendering are your softened rubber 

compound (from mills) and Nylon or 

Polyester from the Dip Unit. 

In this process, the tension, temperature 

and humidity are critical parameters of 

your fabric cords before they are 

calendared with the rubber compound. 

And hence is the reason you will observe 

that the fabric cord is kept in a room 

(where temperature and humidity are 

controlled well) once this raw material 

arrives in your shop floor. 

Then you make this continuous sheet of 

fabric and rubber go through many 

additional rolls to ensure that rubber is 


| CALENDERS | 

12 

penetrated properly between the cords 

achieving the desired adhesion between 

rubber and the fabric. 

The sheets are cut at required angles so that 

the cords are set at predetermined angles 

across the sheet. 

Even inner liners for tyre manufacturing are 

calendered the same way into sheets of 

required thickness and then cut into 

appropriate widths for use in tire 

construction. 

Finally, your calendered fabric sheets are 

wound into rolls with layers of woven fabric 

liner to prevent the surfaces of sheets from 

sticking together. 

B. Steel Cord Calendering 

In the tire industry, steel cord calendering is 

for the radial tires. 

Here, the body plies and reinforcing strips 

incorporate polyester cord that is coated in 

an adhesive liquid. This cord is passed 

between large, heated rolls of a rubber 

calender machine. Woven fabric is similarly 

prepared and calendered for the anti-chafing 

strips. 

Since your rubber compound will not adhere 

to bare steel, the steel cord wires for the steel 

belts are coated with a very thin layer of 

brass. These high-tensile brass-coated 

rubber-encased steel cords (multi-strand 

cables) become the steel belts. 

You pass preset number of steel 

cords under proper tension from 

the creel room on rolls through 

aligning combs into the calender 

where the wires are coated with 

a thin sheet of skim stock rubber. 

You may note that the steel cords come in 

various arrangements like cross-section of 

pairs, triplets and so on. 

The brass-coated steel wires used in the 

manufacture of tire components are also 

extremely moisture sensitive. Hence, they 

must be protected in a temperature and 

humidity controlled environment – right 

from procurement, to during shipment 

and at the tire plant location. More 

importantly, any exposure to moisture can 

result in corrosion and a breakdown in 

rubber adhesion when calendered. 

At your plant, these wires are stored in an 

environmentally controlled 'Creel Room' 

until it is processed in your rubber calender. 

You pass a preset number of steel cords 

under proper tension from the creel room 

on rolls through aligning combs into the 

calender where the wires are coated with a 

thin sheet of skim stock rubber. For 

maximum adhesion, the rubber should also 

penetrate these steel cords. Maximum 

adhesion also means least rusting. 

These steel cords are cut at specified angles 


| CALENDERS | 

and widths for use in tire building process. 

In ground reality, the distance between the 

creel room and your rubber calender 

(varying between 20 – 60 feet depending on 

your layout) is usually not environmentally 

controlled and, hence the wire may be 

exposed to moisture prior to its being 

encapsulated in rubber. 

This problem is worsened by slowdowns, 

temporary shutdowns, humidity spikes and 

failure to adequately control temperature 

and humidity within the creel room. Once 

the belt wire becomes contaminated with 

moisture, it becomes more difficult to 

obtain proper adhesion of the rubber to the 

brass-coated wire. 

The strongest possible bond between the 

rubber and the belt wire is critical in the 

construction of your steel belted radial 

tyres. 

Judging Quality 

So, how do you judge the quality of a 

calendered sheet? 

Well, you could quantify the quality of your 

fabric calendered sheet in terms of your 

pre-desired 

- Thickness of the sheet 

- Spacing between cords 

- Number of cords and 

- Penetration of rubber into the space in 

between cords. 

Recently, an industry friend confided that 

many rubber good manufacturers look at a 

Rubber Calender as a 'mysterious rubber 

machinery'. Is it because of all this nuances, 

I wonder? 

Image: Cross-section of Radial Tyre 

13 


| CALENDERS | 

14 

Image: Rodolfo Comerio 

Functions of Rubber Calendering 

1. Skim Coating or Topping: Here, rubber 

is coated on both sides of the substrate (i.e 

your fabric or steel cords). This operation 

strengthens the adhesion between rubber 

and the substrate. Your process decides 

whether you use a 3-Roll Calender or a 

4-Roll Calender. 

2. Frictioning: Here, you use calendering 

process to force rubber into the fabric 

weave. Frictioning imparts good 

adhesiveness. You deploy 3-Roll Calender, 

where the top and bottom rolls have a 

lower speed than the middle roll. 4-Roll 

Calenders cannot be used for Frictioning, 

because obtaining a speed difference 

between fabric and compound is difficult. 

3. Rolling: Here, you just allow hot rubber 

compound to pass through a 2-Roll Calender 

and get a continuous sheet of rubber of 

thickness 3-4 mm. 

4. Embossing and Profile Calendering: If 

you produce tread sections of cycle tires or 

involved in hand building of foot wear, you 

may choose a Calender with “patterns” on 

the rolls to produce profiled treads or 

patterned sheets. A step forward of Rolling, 

here you press a heavy engraved roll 

against hot rubber compound. You would 

consider this if your sheet needs a 'design' 

look. The engraved design of the rolls is 

transferred to your rubber sheets. 

Calendering operations need critical checks 

to ensure you get high quality products. 


| CALENDERS | 

2-RollCalender 

Types of Rubber Calenders 

A calendar is heavy-duty rubber machinery 

consisting of two or more rolls that revolve 

in opposite directions. The classification of 

Rubber Calenders is based on 

1. The Number of rolls 

2. The Position or Orientation of the rolls 


VerticalTypeCalender 

InclinedorTiltedTypeCalender 

VerticalStackor 

ʻIʼTypeCalender 


» Also known as the “Universal 

Calender”. 

» Highly Flexible in usage. 

» Used for Frictioning and 

Skim Coating. 

» ‘I’ Type is the oldest & most 

common configuration. 

» Also known as the “Modern 

Calender”. 

» Different Configurations. 

» Used for Skim Coating. 

InvertedʻLʼTypeOffsetStackCalender 

OffsetStackTypeCalender 

16 

ʻIʼTypeorVertical 

StackCalender 

ʻZʼTypeOffset 

StackCalender 

Images from different sources only for representation purposes. 

Various rubber calender manufacturers 

offer you different types. Today, you have 

a wide range of new and used calender 

purchase options (see box below) for your 

budget albeit of varying nature of quality, 

features and durability. 

Box: Excerpts from ‘Know Your Supplier’ Editions 

“Pelmar is there to offer a total 

solution. Calendering lines sold 

as is or refurbished, along with 

mixing lines are amongst our 

largest sales chunk” 

Jacob Peled 

Executive Chairman 

Pelmar Engineering Ltd. 

“The wide range of quality new 

machinery made by Bharaj is wellaccepted 

worldwide. We offer 

complete solutions.. I would say that 

our Calenders are high in demand.” 

Amardeep Singh Bharaj 

Director - Sales & Projects 

Bharaj Machineries Pvt. Ltd. 


Information On Equipment, Technology, Innovation & Suppliers 

ReachMachineryBuyersFast.Anytime.Anywhere. 

On-The-Go With Your Info 

InfoPortal|DigitalMagazines|SocialMarketing 

ADVERTISE On 



 

Rubber & Tyre Know A 

Machinery 

World 


LEADER 

In 10 Questions 

Know Your 

Supplier 

rubbermachineryworld.com / tyremachineryworld.com 

Rubber & Tyre Equipment - Accessories 

Technology & Innovation 

Special Edition 


Machinery 

World 

Because we publish digitally on our portal and promote on social 

media differently, Buyers get all information of Your Products & 

Solution anytime and anywhere - on any smart gadgets they 

use (Phone, Tab, Laptop or Desktop). 

1.DISPLAYYourProductsRegularlytoBuyers. 

2.COMMUNICATEYourCompetenciesDifferently. 

3.ATTRACTMoreBuyerstoYourBrandInformatively. 

For more details and your customized advertising, please email us 

at engage@rubbermachineryworld.com 

OptimizedRoIOfYourEquipmentMarketingForRubber&TyreIndustry

| CALENDERS | 

Choose Wisely. Operate Smartly 

8 Common Defects in Rubber Calendering 

And Their Causes 

» Incorrect crowning of calender rolls 

» Excessive wearing of bearings 

» Improper operation of roll bending/zero clearance devices 

A more significant aspect of rubber 

calendering is operating this rubber 

machinery itself. 

» Roll temperature too high 

» High feed bank on to the rolls 

» Compound Stock warmed up for longer duration 

You could have chosen your rubber calender 

wisely but if you do not operate it smartly, 

you are likely to have defects in the 

calendered sheet. 

And when you know the causes leading to the 

defect (refer adjacent box), it becomes easy for 

you to investigate them deeper, resolve and 

continue production. 

» Insufficient break-down of your compound 

» Inadequate temperature control 

» Insufficient compound feed in the banks 

» Roll temperature too high 

» Large nip opening 

» Stock warm up for long time 

» High Compound in the nips 

» Insufficient nip opening between rolls 

» Excess compound in the nip 

» Improper roll crown 

» High compound viscosity 

18 

Image of A 3-Roll Vertical Calender from 

Bharaj Machineries Pvt. Ltd. 

» Improper Roll temperature 

» Improper running speed 

» Low compound viscosity 

» Improper warming of the compound 

» High viscosity compound 

» Improper warm up, high bank 

» Non uniformity of warm up 

» Lower roll temperature 

» Lower temperature in one of the rolls 

» High friction ratio 

» High calendering speed 

» Use of anisotropic fillers 


| CALENDERS | 

7 Do's (And Don'ts) In Calendering 

Choosing the right rubber calender is 

important, learning to operate it smartly is 

equally key for your success with this 

machine. (Refer adjacent box) 

» Use lab approved fabric and compound only. 

» Clean the mill and calender guides including the 

equipment surrounding area before starting unit. 

» Load single strip of compound to both the cracker 

mills. Then feed these compound to your holding mill. 

» Always keep minimum compound in calender nips 

and mills. 

» Apply correct bleeder yarn. 

» Put identification tags before storing your calendered 

fabric in racks. 

» Close cooling water lines to mills when mills are not 

running 

Image: Reconditioned Calender 

(JM Machinery) 

» Do not over load your two-roll mills and calender nips. 

» Do not use held up compounds and dipped fabric. 

» Do not stop unit with fabric in the line. 

» Do not throw sheeted-out compound on the floor. 

» Do not store calendered fabric on floor. 

» Do not use damaged liner / baggy liner. 

» Do not run mills with cooling water lines closed. 

Solving issues with Calender Gauge 

Control 

Calender control issues directly affect your 

ability to properly control the rubber gauge 

or to produce a rubber sheet of consistent 

thickness. 

While these sources are closely related, for 

quicker understanding, you may visualize 

and attribute the two main sources of 

variations in calendered gauge (or 

thickness) as, 

A. Mechanical Induced – variations when 

your calender is not operating under 

any load and are at ambient conditions. 

B. Force Induced – variations when your 

calender is in operation or is 

programmed to follow a set-process for 

your product under manufacturing. 

A. Mechanical Induced Variations 

Mechanically induced Calender Gauge 

variations relate directly to your rubber 

calender's mechanical condition. Thus it's 

basically a maintenance issue. 

While there are many maintenance issues 

that could affect your calender 

performance, the following five directly 

affect your rubber sheet's calendered gauge 

1. Grind Profile of Calender Roll (Roll 

Crowning) 

You must periodically grind the calender 

rolls to establish the proper profile. Your 

selected crown profiles is based on the range 

of your rubber compound hardness, type of 

center compensation such as cross-axis or 

rolls bending, and roll width. 

19 


| CALENDERS | 

a) No Crown - No Load b) No Crown - Uniform Load 

c) Uniform Load - Correct Crown d) Uniform Load - Correct Crown 

by bending roll to frame 

20 

e) Uniform Load - Correct Crown 

by bending reaction roll pair 

Source: GEA 

f) Roll Crossing 

The forces that separate the rubber calender 

rolls to bend apart in the center are partially 

compensated for, by grinding the center to a 

larger diameter. When the grind profile is 

incorrect it will be difficult or even 

impossible for you to achieve a consistently 

flat-calendered rubber sheet. 

2. Eccentricity of Calender Roll or Run-out 

at Ambient Temperature 

Your calender rolls must be round and free 

of run-out at ambient temperature. Any run 

-out of the individual calender rolls will be 

amplified as the high spots and low spots 

periodically match up between the roll 

pairs. You can easily check this with dial 

indicators when the calender is running 

without rubber and with a small nip gap 

between the pairing rolls. 


IKATAN TEKUN SDN. BHD. 

Your Partner in MALAYSIA for Rubber & Processing Machinery 

“Complete your Plant 

with your desired 

technology to your 

complete satisfaction 

on-time through us.” 

For your green-field and brown-field expansion 

or research projects in raw rubber and other 

technical rubber goods, we can source for you 

the right machinery to meet your technology 

requirements, and be your single-window 

support for after-sales service communication 

and training in Malaysia. 

For crucial projects, we train our personnel on 

the machinery we supply, to give you quick 

support. 

In addition, we are established and licenced 

contractors in Mechanical, Telecommunications, 

Electrical and Civil Works. Hence, we offer you 

on turnkey basis - from equipment supply, 

material handling at site, equipment relocation, 

erection and installation, services and utilities 

to equipment commissioning. 

Contact me today to know more on our 

team, the equipment brands we partner 

with, our esteemed clients and full range 

of services for your rubber related projects. 

IKATAN TEKUN SDN. BHD. 

1st, Floor, Bangunan Sapura,Lot 2, 

Jalan Enggang, Kawasan Perindustrian PKNS, 

Hulu Kelang, 54200, Kuala Lumpur, Malaysia. 

Tel: (+6) 03 - 425.6 5.589 | Fax: (+6) 03 - 425.7 5.589 

AUTUS CONSULTING @2016 

Ahmad Fezal Bin Zakaria 

Sales & Project Manager 

* fezal@ikatantekun.com 

) (+6) 017-362.79.71

| CALENDERS | 

3. Condition of Calender Roll's Bearings 

You must ensure that your Rubber Calender 

roll bearings does not have excessive runout. 

Modern calenders employ precision anti 

-friction bearings with very small radial 

clearances. Excessive bearing clearance will 

result in the roll shifting during operation 

because the roll separating forces vary. This 

could appear as calender roll surface runout 

and will adversely affect your ability to 

control calendered gauge. 

4. Condition of Calender Roll's Water 

Passage 

Most modern calenders have drilled rolls. 

A drilled roll has water passages across the 

roll face beneath their surface. These water 

passages effectively forms a radiator-like 

heat exchanger around the periphery of 

your calender rolls. 

In an event when these passages become 

plugged, then non-uniform heat transfer 

will occur. And this result in a thermal 'outof-round' 

condition for your calender roll 

which subsequently has has the same effect 

as if the rolls were machined 'out-of-round'. 

You may avoid this situation by using only 

treated water and ensuring that the rolls 

are periodically flushed. You could also 

check this condition by comparing the roll 

run-out or eccentricity at ambient 

temperature with that at normal operating 

temperatures of your Calender. 

5. Condition of Calender Roll's End 

Actuator 

Of the different variants - manual, motordriven 

and hydraulic nip gap adjustments 

- electric screw actuators are the most 

common type of calender roll endpositioning-system. 

The screw and nut 

operate under very high loads and thus, 

you will observe, that they experience 

significant wear even with proper 

lubrication. As these actuators wear, 

backlash develops. 

When the backlash increases, the response 

to small changes or corrections deteriorate. 

Further with increased backlash the 

number of corrections required would 

increase, which in turn causes additional 

wear. 

23 

Image: Three-Roll Calender (Left) and Spare Calender Rolls With Bearings (Right) 


| CALENDERS | 

Image: From Web 

24 

Rubber calenders that have fixed speed 

electric motors with mechanical brakes 

require periodic maintenance, particularly 

the brakes. Because sticky brakes will 

adversely affect your gauge control results. 

Thus, proper maintenance of all the above 

systems is crucial to your rubber calender 

performance and solves issues with 

gauge control that are mechanically 

induced. 

Proper maintenance of all the 

above systems is crucial to your 

rubber calender performance 

and solves issues with gauge 

control that are mechanically 

induced. 

B. Force Induced Variations 

Force induced variations result from the 

way your calender is operated. This is also 

an outcome from previous process steps 

such as your feed mill operation and 

compound consistency from rubber mixing. 

The separating forces generated during 

calendering are quite high! For example, if 

you have a 66 inch calender roll and 

producing 60 inch wide rubber sheet, the 

separating forces are in the range of 72,575 

Kg (approx. 160,000 lbs) to 136,000 Kg 

(approx. 300,000 lbs) at each actuator. 

Such high forces literally stretch your 

calender frame. Variations in these forces 

will therefore vary the amount of frame 

stretch and thus vary roll position and 

calendered gauge of your rubber sheet. 


| CALENDERS | 

Here are five tips on how you could solve 

issues of calender gauge control from force 

induced variations. 

1. Keep the rubber calender running. 

that are open is higher. This differential 

heat transfer leads to different 

temperatures on your calender rolls. And 

therefore different degrees of calender 

roll expansion. 

Because stoppages cause your calender 

rolls to become egg-shaped, that in turn 

introduce significant gauge thickness 

variation. 

When you stop the rubber calender, the 

heat loss from the rolls is not uniform 

around their surface. Heat loss along the 

face of the rolls near adjacent rolls is 

minimal, while heat loss in other areas 

If you have a calender with rolls that is 

24 -30 inches in diameter, even a few 

degrees of expansion will result in 

‘out-of-roundness’ of each roll that you can 

measure. This is true when the calender 

is empty but even more so when there is a 

hot bank of rubber between the rolls. If 

you stop the calender for longer period, 

this condition worsens further. 

26 

Image: India’s first fully Automatic Tyre 

Cord Calender Line from Bharaj Machineries 


| CALENDERS | 

Image Source: Web 

Your calender rolls run at different speeds. 

This means that periodically the high and 

low spots on the rolls match up. When high 

spots of adjacent rolls match up, you get 

thin gauge spots on your calendered sheet. 

When the low spots match up a thick spot is 

observed. So calender stops induced 

variation results in an effective doubling of 

any roll “out-of-round” or run-out error. 

Typical short-term thermal out-of-round 

gauge variations are ± 0.0005 to .002 inches. 

Though thermal run-out is gradually 

reduced as the calender runs, it takes 15 to 

25 minutes for variations to be eliminated. 

Experts recommend you to adopt the 

following steps to minimize ‘thermal 

run-out’ of rubber calender, 

- Keep the calender running during warmup. 

If not done, severe thermal run-out can 

be introduced. You need to remember that 

the calender nip gap between adjacent rolls 

will be reduced as the rolls enlarge with 

their temperature increases. So, a good 

practice is to open your rubber calender at 

least 0.10 inches (2.54 mm) before starting 

to increase the roll temperature above 

ambient. Keeping the calender rolls turning 

during warm-up and cool-down also 

eliminates the possibility of warping the 

rolls. 

- Minimize calender stops. 

- When you stop the calender for longer 

time, remove the rubber from the banks. 

This is a good operating practice for the 

rubber compound as well. 

- When leader is going thru the calender, 

dropping off tension and allowing the 

uncoated fabric or leader to go slack will 

permit running the calender during delays 

and personnel breaks. This will 

dramatically reduce thermal run-out. 

27 


| CALENDERS | 

2. Increase the temperature by 5 degrees 

Celsius when you stop the rolls. 

loop. In this condition the roll surface 

temperature is below the water temperature. 

28 

Because this helps to maintain a more 

uniform roll surface temperature. 

You need to realize that the TCU 

(Temperature Control Unit) of your rubber 

calender controls the temperature of the 

water exiting the rolls and not the 'roll 

surface temperature'. This is an important 

distinction. 

Visualize these two scenarios – 

Scenario 1 – When the calender is not 

processing rubber (i.e. during warm-up and 

when the calender is stopped), the roll 

surface is losing heat to the atmosphere. 

Here, the TCU is actively heating the water 

Scenario 2 – When the calender is running 

and processing rubber, heat is being 

generated. Here, the TCU is cooling the water 

loop. In this condition the roll surface 

temperature is above the water temperature. 

From the above, you will realize that for a 

constant water circuit temperature, the roll 

surface temperature swings (above & below 

the water temperature) between the 

calender normal running condition and 

when the calender is stopped. This 

difference in roll surface temperature 

means that your rubber compound is being 

processed under varying conditions. 

Shrinkage and other properties of your 

processed compound will therefore vary. 

Image Source: Pelmar Engineering Ltd. 


| CALENDERS | 

To minimize the differences from such 

processing condition variations, the roll 

temperatures should be increased whenever 

the calender stops. The temperature 

increase should be gradual. Your specific 

value should be experimentally determined 

by comparing roll surface temperatures in 

normal operation and after the calender has 

been stopped for 20 minutes. 

3. Limit the temperature rate of change at 

all times to a maximum of 3 degrees per 

minute. 

Because faster rates can damage or warp the 

rolls. 

the TCU circulation pumps before the 

calender reaches ambient is not considered 

good practice. 

If the temperature control system has rate 

of change limits properly set, cooling down 

is easy, since all the operator must do is to 

lower the temperature set points to ambient 

and then 60 to 90 minutes later return back 

to the operator console to turn off the TCU. 

4. Minimize speed changes. 

Because changes in your calender speed 

result in gum wall gauge thickness 

variations that are undesirable. 

30 

The control system on the TCU should be 

designed and operated to limit the rate of 

temperature change for each calender roll 

water circuit to 3 degrees per minute. Faster 

rates of change do not allow for equalization 

of mechanical expansion throughout the 

rolls, bearings, and calender frames. 

Differential expansion can stress various 

components of your calender. In extreme 

cases, they can actually crack or warp the 

rolls, or even damage the bearings. 

Heating usually is limited by the available 

heating capacity but the cooling system 

frequently has the capacity to rapidly cool 

the rolls and therefore also has the potential 

to cause damage if not limited to 3 degrees 

per minute. 

Again, it is important to keep the calender 

running during warm-up and during cool 

down. Stopping the calender and turning off 

When the calender is running there are 

forces generated that try to separate the 

rolls, as explained earlier. And these 

separating forces are proportional to 

calender speed (although the relationship 

is not linear). 

The hardness of your rubber stock and 

bank temperature determines the 

magnitude of separating forces. The 

thickness of the gum wall being calendered 

also affects the separating force – thinner 

gum walls generate higher separating 

forces. Separating forces of 160,000 to 

300,000 lbs at each actuator literally 

stretches the calender frame. When the 

forces vary, the amount of stretch varies. 

This further results in the roll-gap varying 

that in turn causes the gum wall gauge to 

vary. 

Hence, speed changes should be avoided 


AMCL MACHINERY LIMITED 

SERVICE TO THE NATION FOR FOUR DECADES 

Product Range 

• Rubber Mixer – 76" liter and 270 liter. 

• Mixing Mills – 16", 22", 26" and special sizes 

• Hot feed extruders – 6" and 8" 

• Rubber Calenders – 2/3 rolls. 

• Bias Tyre Building machine – RB1/RB3 

• Automatic LCV Tyre Building Machine – RB1619 

• Automatic Truck Tyre Building Machine-RB2022 

• Mechanical Tyre Curing Presses – Scooter to Truck size 

• Bladder Curing Presses 

• Tube Splicers 

For all your enquiries please contact: 

AMCL MACHINERY LIMITED 

Works: Plot No.A1/1, MIDC, Butirobi-441122, Nagpur 

Mumbai office: 202, Ackruti Centre Point, MIDC Central Road, Andheri (East), Mumbai-400 093. 

Contact person: Mr. S.H. Mehta 

Mobile No. +91-9004697430. Email: shmehta@amcl.in Website: www.amcl.in

| CALENDERS | 

Image Source: Pelmar Engineering Ltd. 

32 

to the extent practical. A speed reduction 

from 45 mpm (meters per minute) to 9 mpm 

can result in a gauge decrease of approx. 

0.002 inches. Similarly, the vice-versa holds 

for a gauge increase with roll speed increase. 

Calenders are of different types. And 

different calendars have different degrees 

of frame stiffness so the quantum of the 

gauge change for a given speed change will 

vary accordingly. 

5. Mill management 

Maintain consistency. 

You can substantially reduce gauge 

variations by feeding the calender 

consistently. 

A consistent, uniform, dwell times on the 

cracker and feed mills, as well as consistent 

bank size, will give consistent rubber stock 

temperatures and work history. The stock 

temperatures, bank sizes, and work history 

directly influence calender roll-separating 

forces. 

When you minimize variations in these 3 

important process parameters, you will 

minimize variations in roll separating 

forces, and this in turn will minimize gauge 

variations of your calendered sheet. 

Further, good mill and bank control 

practices also give improved uniformity for 

other final calendered gum and/or fabric 

properties. 

When you feed to the calender, you must 

also ensure that the rubber bank does not 

have areas that could stagnate. Because if 

rubber remains in the bank on the calender 

for an excessive amount of time, it will 

partially cure and become much harder. 

Edge trim process that returns to the bank 

and stagnates is a common source of this 

problem. 


| CALENDERS | 

Such cured and hardened compound will 

introduce gauge variations as well as 

negatively influence other properties of 

your calendered material. In extreme 

cases, burnt lumps will appear in the 

calendered gum. 

Presence of hard stock makes it difficult 

to properly penetrate the cord and may 

cause cord disturbance and improper 

cord distribution. 

In such cases the cushion force causes 

lateral movement in the nip and this 

further results in cord displacement that 

is visible. Paired cords are often the first 

indicator. You will observe that the 

calendered thickness will be heavy and 

there will be cord displacement or 

irregularities. However, the weight of test 

samples will not be significantly affected. 

Localized cord disturbance in cord 

distribution does not usually affect fabric 

weight, whereas redistribution of the cord 

does. Overall cord distribution problems 

can affect fabric weight in the case of fabric 

calenders. 

For example, incorrect cord distribution 

may reduce the average EPI (Ends Per Inch) 

in the center of the fabric and increase the 

EPI (Ends Per Inch) on the outer edges. This 

will affect fabric weight and thickness – the 

weight of the center would be light, while 

the outer edges would be heavy. 

In steel cord calendering, visible cord 

33 

A) Uniform Cord Spacing - Uniform Top and Bottom Rubber Coat. 

Image Source: GEA 

B) Cords spread at the edge of the sheet. 

C) Cords paired. Top or Bottom Rubber Coat is heavy in the center. 


Information On Equipment, Technology, Innovation & Suppliers 

| CALENDERS | 

Image: Bharaj Machineries Pvt. Ltd. 

34 

displacement and cord pairing after the 

cushion nip is to be expected in the areas 

where the cord EPI count is excessive. 

Training 

Your guiding principle for calender line 

operation should be consistency and 

continuity. If all the inputs to your 

calendering process are constant, and your 

installed machinery is functioning correctly, 

you can produce quality goods meeting tight 

specification tolerances. Your operators need 

to acquire knowledge on how the rubber 

calender works, how changes in process 

variables affect outcomes, and how changes 

in machine and/or process conditions can 

beat those changes. Training them to run the 

calender under complete manual control 

Your guiding principle for 

calender line operation should 

be consistency and continuity. 

will make them know enough to understand 

the importance of maintaining as close to 

steady-state operation as possible. Further, 

this knowledge will also help them to 

operate the line without the gauge or the 

automatic set-up, if they ever need to do so. 

Summarizing, the nuances in the world of 

rubber calenders is an interesting subject 

and as you understand its operations 

deeper, the 'mysteriousness' of this rubber 

machinery disappears faster. 

RMW 



 

........... And More 

NEW INFORMATION 

DIFFERENTLY 

Every Month With 


Machinery 

World 

LEADER 




Rubber & Tyre Machinery Technology World | & JUL Innovation 2016 

Know Your 

Supplier 




Machinery 

World

WhatIsYourStoryToday? 

Every Machinery Has.... 

Every Technology Has... 

And As Equipment Supplier, 

YOU Denitely Have... 

A Story 

Let Equipment Buyers Know You, Your Products & Your Technology Better. 

ReachMachineryBuyersFastIn3Steps 

1.DISPLAYYourProductsRegularlytoBuyers. 

2.COMMUNICATEYourCompetenciesDifferently. 

3.ATTRACTMoreBuyerstoYourBrandInformatively. 

ADVERTISE On 

RUBBER Rubber 

Machinery 

World 

M 

http://rubbermachineryworld.com 

M 

TYRE Tyre 

Machinery 

World 

M 

M 

http://tyremachineryworld.com 

And SELL MORE 

Because we publish digitally on our portal and promote globally, 

Buyers get all information of Your Products & Solution anytime 

and anywhere - on any device (Phone, Tab or Computer). 

For more details and your customized advertising, please visit 


Or email us at engage@rubbermachineryworld.com 

InfoPortal|DigitalMagazines|SocialMarketing 

Equipment Marketing Redefined 


Machinery 

World 


LEADER 


Know Your 

Supplier 



Technology & Innovation 



Machinery 

World 

Information On Equipment, Technology, Innovation & Suppliers

KELACHANDRA MACHINES 

(MFRS. OF RUBBER INDUSTRIAL MACHINERY) 

Chingavanam - 686 531, Kottayam, Kerala. India. 

Phone Off: +91- 481-2430325. Fax: +91- 481-2430596 

e-mail: km1912@gmail.com

| INSIGHT | 

This section is bought to you in association with our brand display partners 

37 

7 PROVEN STRATEGIES 

TO METHODICALLY GROW 

YOUR BUSINESS 


38

Source: Web 

39

Attention: Equipment Buyers & Users 

Rubber And Tyre Machinery 

Now Has An Online Address 


Machinery 

World 

M 


M 

TYRE Tyre 

Machinery 

World 

M 

M 


- Power Your Business Forward With Authentic Information 

On 

- Equipment & Allied Machinery 

- Technology 

- Equipment Suppliers 

- Read, Absorb & Implement Ideas From 

- Insightful Interviews Of Leaders 

- Informative Articles 

- Special e-Editions & e-Books 

- Short Updates Curated from the World Of Machinery Every 

Thursday In Your Inbox 

- Resourceful Downloads For Day-to-Day Use 

- Plan For Your Conferences & Expo from event dates 

- Book Store with Best Rubber Books For Your Quick Buy 

- Key Documents/Directories to take Powerful Business 

Decisions Available For Purchase. 

- Left-Oriented Clean Layout for your easy reading. 

- Follow Us on Twitter, Google+, LinkedIn & Pinterest. 



FREE Access On All Your Devices 

JOIN OUR READERS FROM 130+COUNTRIES 

SUBSCRIBE TODAY FOR FREE & BENEFIT

GET CUSTOM MACHINED 

ROLLERS, SCREWS, FIXTURES & MOULDS 

FOR ALL YOUR RUBBER AND 

PROCESSING MACHINERY. 

AT OUR STATE-OF-THE-ART CNC MACHINING 

CENTERS, WE GUARANTEE YOU 

■ IN-HOUSE CAD CAM STUDIO 

■ 3 AND 4 AXIS MACHINING CAPABILITIES 

■ ACCURATE AND RELIABLE INSPECTION 

REPORTS THROUGH IN-HOUSE CNC CMM 

■ SKILLED AND TRAINED MANPOWER 

■ TIMELY DELIVERY 

■ 24x7 POWER BACK-UP 

UNFAILING PARTNER AND DEPENDABLE SUPPORT 

FOR YOUR DESIGN TO MANUFACTURING NEEDS 

AUTUS CONSULTING @2016 

Excellent 4th Axes Precision CNC Machining Capability for Customized Heavy Rollers. Please contact 

SubAero Precision Machining 

(An ISO 9001:2008 Certified Company) 

HURCO DCX 32 Vertical Machining Centre 

Corp Office: 8/Trivedi Niwas, New Nagardas Road, 

Andheri (East), Mumbai - 400 069, India. 

Ph: +91-22-28256599, +91-22-28378478 (Fax) 

www.subaero.com | Email: info@subaero.com

Stay Updated On Rubber & Tyre 

Machinery And Their Suppliers. 

INFORMATION PORTAL | E-MAGAZINES | INTERVIEWS | KNOWLEDGE PARTNERS | DOWNLOADS 

........... And More 

Rubber And Tyre Machinery 

Now Has An Online Address 


Machinery 

World 

M 


M 

TYRE Tyre 

Machinery 

World 

M 

M 


INFORMATION ON EQUIPMENT, 

TECHNOLOGY, INNOVATION & 

SUPPLIERS 

........... And More 

Know More On EQUIPMENT SUPPLIERS And Their SOLUTIONS For YOU 

KELACHANDRA 

MACHINES 

racsol.com 

Practical Solution 

www. 

........... And More 

Email: rubbermachineryworld@gmail.com 

©2016 – ePublished by Rubber Machinery World in JULY 2016 

Content For Free eDistribution & Download

The Art of Owning & Operating Rubber Calenders

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?