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The Only Reason Why Rubber Calender Was Unpopular for 100 years Since it’s Invention

Calendering is one of the oldest rubber processing technologies. The Rubber machinery that helps you do calendering is known as a Calender (…obviously!!).

The word ‘calender’ itself is a derivation of the word κύλινδρος kylindros – the Greek word that is also the source of the word ‘cylinder’.

In 1836 Edwin M. Chaffee, of the Roxbury India Rubber Company, patented a four-roll 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.

And, so the Calender was never ‘popular’ when it was first invented over 2 centuries back. Here’s why.

Rubber Calender 1

Collage By Rubber Machinery World

Calendering is a mechanical process by which rubber is pressed into textiles (cloth, fabric, tire cord) forming composite sheets.

In this process, you pass pre-selected fabric and rubber through a series of rolls to flatten, smoothen and sandwich the materials.

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.
  • On the other hand, a ‘supported’ sheet has textile fabric or steel cord coated with a film of rubber (aka “skim stock rubber”) on both sides and into the material. Supported rubber sheets give you higher strength or tear resistance.

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 very tough. So you will find it difficult to fulfill the thickness variation across the calendered ply and the cord density.

The calender never did become very popular when it was first invented mainly because it was difficult to adjust the desired gap between rolls. Consequently, it was difficult to get an accurate rubber sheet thickness.

Hence, the process did not become popular till the calender machines became easier to adjust (i.e until the 1930’s).

Rubber Calender Line

Since then, features have evolved. Modern calenders’ can achieve tolerances around ±0.005mm and their lines are adaptive for most sophisticated precision requirements of your product.

What do you think?


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Here’s Why TCU Is An Irresistible Ancillary For Your Rubber Machinery And Worth Your Investment.

TCU or Temperature Control Units are ancillary equipment to your rubber machinery that control process temperatures during rubber processing. During rubber processing, you continually seek optimal temperatures for the best product quality.

A TCU achieves temperature control by circulating water or an oil based fluid through the process application (in a closed loop). This results in heating of the application and temperature control of the process.

Temperature control units service a single process at any one time. In rubber industry, water is most popular circulating media.

For example, you have Three-Zone Water TCU’s for your internal mixer where One Zone supplies water to the Rotors, Second Zone to Drilled Sides (or Mixing Chamber) and Third Zone to Discharge Drop Door (and Floating Weight, RE Plates as appropriate to the mixer model). Usage of TCU in an intensive internal mixer is found to improve carbon black dispersion, eliminate first-batch-effect, maintain batch-to-batch consistency of your rubber mix compound, increase productivity, and reduce machine stress (which in turn increases the life of your internal mixer).

Similarly, you have 4 or 5 Zone TCU’s for your Extruders, where each of the zones supply water to screw, forward and rear barrels, die head, feed roll, etc as is required for your rubber extrusion process. Or you may have Two-Zone TCU for open two-roll mixing mills where each zone supplies water to your peripherally drilled or cored rolls. Most Rubber Calenders also have TCU supplying water to the rolls to control the calendering process temperature.

TCU for a 3-Roll Calender

3-Zone TCU for a 3-Roll Vertical Calender – Image from Bainite Machines Website

A properly installed, operated, and maintained TCU system gives you years of reliable operation.

Each TCU is a self-contained system consisting of a centrifugal pump, electric heater, cool/vent solenoid valve, electrical control, including a PID microprocessor controller and thermocouple along with standard safety devices like a mechanical over temperature safety thermostat, a pressure relief valve, motor overload protection, a low pressure cut out switch, etc.

Temperature Control Units come both in portable and robust sizes (depending on the application) with a variety of different control instruments, heater sizes, and cooling vales.

A Compact TCU

Compact TCU – Image from AEC Website

And you are right when you imagine that the portable TCU’s are visually appealing and popular because of their compact size.

At your installation site, you need to provide adequate water (from portable or central chillers or towers) to these TCUs from your plant water supply source. Check your manufacturer’s operations manual to verify the recommended water pressure requirement. This is important because lower than recommended water pressure can cause pump cavitations while excess pressure can damage internal components.

The pump in your TCU is used for rapid circulation of a relatively small amount of water. This in turn ensures close and uniform temperature differences between the delivery and the return lines.

You use temperature control units, when you want to preheat a process to the desired operating temperature. The heater and  cooling valve works together to give fast and accurate response to bring the water up to desired temperature or to change the settings when needed. This controls your circulating water temperature.

Here is an animation, that I found on the website of Sentra Temperature Controllers. It is quite informative and I hope you too like it. (Click on the picture to start animation)

Advantage Make TCU

Upon reaching your desired operating temperature the TCU can continue to add heat or convert into a cooling device by exchanging a small amount of circulated water with cooling water from an external source. Modern TCU have the controls wherein cooling water is precisely metered into the system by the cooling valve.

Most TCU’s in rubber industry for your machinery has temperature control from 30° to 300°F and designed for easy maintenance.

Summarizing, rubber processing under optimal temperature conditions is a must for your final product quality. And the features of TCU makes it irresistible as an efficiency enhancing ancillary equipment, which control process temperatures on your rubber machinery. Thus worth your investment.

Do you agree?


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Peripherally Drilled Rolls or Centrally Cored Rolls?

Do you use centrally cored rolls or peripherally drilled rolls in your two-roll mixing mills? Or a combination of both?

Roll selection for a mixing mill is of decisive importance for the quality of many high-tech products manufactured by the rubber industry. Open two-roll mills in rubber processing are recommended when quick cooling for the batch being mixed is sought, say for example in final mix compounds.

Generally, these rolls are made of Chilled Cast Iron (CI) through a process of vertical casting. Chilled CI has greater resistance to deflection and uniform heat transfer characteristics. Depending on the presence or absence of alloy, the hardness of the outer working (chill) zone could be in the range of 460-650 HV with a thickness 12-20 mm.

Basis the application, manufacturers take extreme care on the properties of the rolls that include breaking strength from journals and core material, thermal conductivity, surface quality and wear resistance of the roll, overall machining and surface quality.

As these rolls operate at high speeds, precise concentricity with proper balancing of rolls is a prerequisite for efficient utilization of material and energy. The surface quality of the rolls is crucial for the products to be produced. The smoother and more precise the rolls, better the product.

Viscous deformation of the rubber compounds occurs between the rolls of mills during mixing and mastication. This generates heat that needs to be removed through effective cooling. Hence, water circulation passages for cooling are an essential feature of the roll design in rubber mills. These passages allow a pre-defined circulation of the cooling agent (mainly water) and ensure that the temperature can be kept within a prescribed tolerance over the entire face length of the rolls.

Two designs are normally available – centrally cored rolls and peripherally drilled rolls. Peripherally drilled rolls are possible for diameter greater than 150mm (or 6 inches). The cross-section of a centrally cored roll is easy to visualize. But, ever wondered how the insides of a peripherally drilled roll looks like?

Well here is with a sectional view with water flow.

Peripherally Drilled Roll

The water entering into the roll is cooler (blue colour) and as the heat transfer occurs, the water temperature rises gradually (red colour at exit).

The efficiency of heat transfer is relatively higher in the case of peripherally drilled rolls than in centrally cored rolls due to close proximity of the water channels to the roll surface. In peripherally drilled rolls, the passages for heat exchange are provided approximately 25mm under the roll surface and can vary nominally between manufacturers. Reputed roll manufacturers like Walzen Irle, Leonhard Breitenbach and Karl Buch, in their decades of existence, have built their own standards. Roll manufacturers are also available in China, Taiwan and India for various sizes.

The manufacturing processes and costs involved in producing a peripherally drilled rolls is relatively high, hence they are priced higher than cored rolls. Your choice of peripherally drilled or cored rolls depends on the quality of rubber processing required in mixing mills and the marketability of your rubber products for a price that profitably covers your investment.

Any state-of-the-art Calender in rubber processing also use peripherally drilled rolls for its stated advantages.


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Rubber Machinery and Make In India

The new government of Narendra Modi has enhanced India’s image in the world economy. And a new thrust is being built-up in our manufacturing arena. The flavor of the season has been the rising roar of lion (read “Make in India” logo). Their Facebook page has garnered 2.1 million ‘Likes’ while “#EASEOFDOINGBUSINESS” is popular hash tag on Twitter, reflecting the aspirations of a billion dreams.

And why not?

We have a stable and strong pro-industry government. Global economy is picking up, and India’s core advantages continue to be strong. The government has started well, and already made few minor yet important changes to improve manufacturing sector. Their intent to address obstacles across infrastructure, labour reforms and ease of doing business along with marketing of Brand India are much awaited heartening measures.

Industry Scenario

Rubber machinery comprises of equipment used for Compounding, Mixing, Shaping, and Vulcanizing.

This industry in India manufactures mixers, mixing mills, calenders, extruders, tyre curing presses, tyre moulds, tyre building machines, bias cutters, injection moulding machine, etc.

Estimated at USD 405 million (in 2014), the total market in India is expected to grow at 20% CAGR to USD 580 million by 2016.

According to the Ministry of Heavy Industries (MHI), currently there are 19 units in the organized sector for the manufacture of rubber machinery required for tyre/tube industry. The Indian rubber machinery manufacturing industry is a net exporter. Up to 100% FDI is allowed under the automatic route. Technology collaboration is also freely allowed.

The Indian Rubber Machinery industry is mostly a cluster of SME’s that epitomises the famous “jugaad” entrepreneurial spirit. Over the years, some have grown and compete globally. I wear the name of one such home-grown brand on my chest – Bainite Machines.

Today, some leading global brands in rubber machinery have manufacturing presence in the country through JV’s, wholly owned subsidiaries or technology license arrangements.

Opportunities Galore

Industry has witnessed growth in tandem with our growing economy in the past. Domestic manufacturers have 60% share in the machinery market. Share of imports is 40%, mainly from Far East on account of low price and shorter delivery.

An accepted approach to purchase equipment today follows this thought process – customers need to look West (Europe) for advanced technological machinery if the price tag is affordable or look to China for a low-cost replica.  Another option is to import used-machinery, which is being discarded by the developed world, at an attractive price tag.

Should this approach be refined? Yes, let me explain.

Increased deployment of used-machinery will render our domestic rubber processing industry inefficient in the long run. Because, rubber processors in the developed world are replacing the older machines with new technology machines under the compulsions to reduce the carbon footprint. Old/Used machinery has high operating cost, higher energy consumption as well as loss of productivity from higher maintenance. One industry friend said this aptly “its wishful thinking to assume another enterprises’ liability (used-machinery) can be your long-term asset (productive machinery)”.

Is it then China? Wait!

Recent statistics are interesting. They reveal China is slowly loses its manufacturing edge. And the reasons are multiple. The labour there aspires to work in hi-tech factories creating workforce shortage for labour intensive machine shops. Wages are rising over 10% per year higher than Indian labour cost increase. The rising Yuan (over 7% against dollar in last three years) makes China’s exports costlier while dropping Rupee (over 26% against dollar in last three years) makes India’s imports costlier. Reports of various forex experts suggest China can afford to let the Yuan strengthen a little bit more while Rupee will remain currency competitive as along as India’s trade-deficit is under control. Also for world-wide importers, shipping costs out of Chennai or Mumbai to most ports of the world are competitive (sometimes even lower) to that from Chinese peers.

Most tire producers around the world and few rubber product manufacturers standardize their production processes across their multiple plants. They adopt one machinery manufacturer for one particular production step and develop them to their customization requirements. This is a win-win situation for both the machinery manufacturer and end user.

It’s an acknowledged fact that Indian machinery manufacturers meet 95% of domestic rubber processing industry needs on technology and product range. Our product technologies are at par with leading brands of developed world albeit offered at great cost advantage.

This is also because leading manufacturers know their fundamentals well. We understand machinery and also rubber processing.

The importance of metallurgy, selection of the right material technology, process technology and appropriate designs that bring out machine systems which are long lasting is paramount to us. And hence, we can design and manufacture customized equipment for our customers. This is definitely our niche as compared to competitors of Far-East.

So, I feel, Indian rubber machinery industry is well positioned on the technological and logistical fronts to offer customized USPs in both domestic and export markets.

Sprucing-up

Indian machinery manufacturers have undertaken capacity expansion, upgradation in technology and adoption of best manufacturing practices to compete effectively – both in the domestic and export markets.  At Bainite Machines, we had started a phase-wise replacement of conventional machines with CNC’s since 2011. We invested in latest design and simulation software to build newer machineries like TSS from scratch, introduce latest B-Turbo tangential rotors, and offer value added sophistication to our regular machineries.

The focus is shifting to automation to create customer value. Smart automation on rubber machineries improves productivity of our customers and enhances operator safety. For example, we developed fully automatic Mixing Room technology requiring only one operator and have highest levels of safety interlocks in the complete processing line. For a large rubber processor, adopting technology and automation is sustainable because the benefits include lower cost of production (cost/kg), consistence in quality, superior aesthetics and reduce defects in throughput production.

Operator-friendly, energy-efficient, machinery that are safe, meets global compliance standards and satisfies the technology appetite is the need of the hour. Bainite Machines recognizes this and design customized machinery. Our recently built Hydraulic Ram in Mixers has a Ram up and down time of less than 3 seconds which in conventional mixers used to be 7 – 8 seconds. In a mixing cycle, there are 2–3 Ram Up and Down operations and hence this 4 seconds saving in each stroke is a tremendous boost to productivity.

Our tagline “Technology That Drives Industry” encapsulates Bainite’s dreams to be a technology driver and is equally fuelled by a passion to position an Indian Machinery manufacturer as a significant force to reckon within the global rubber/tire machinery market. Similar aspirations prevail among my industry friends.

What Next – Two Way Bridge?

Indian Rubber Machinery Industry requires further investments to raise the production volumes and technology to global scale. Volumes will give price competitiveness that our customers expect from us. Government has taken few initiatives to fuel growth and support manufacturing industry.

Equally important is the Indian customers’ recognition of the fact that machinery manufacturers must invest a part of the revenue to R&D efforts. This helps them to improve consistency, improvise continuously on quality, innovation and development of new machines. More importantly, customers can expect prompt after-market (spares and service) support when the machinery manufacturing is local.

So, squeezing the domestic machinery manufacturer to unviable price levels during commercial negotiations citing Far-East competition kills all future advancement efforts. This could then become an impediment to your progress as well tomorrow. Indian Rubber Machinery Industry needs your patronage today more than ever.

We have already demonstrated our competence and quality to the world. Rubber processors across the world are regularly reposing their faith on the Indian Rubber Machinery Industry, eventually making us a net exporter. So, there is no restraint that you could think of to establish this two-way bridge for mutual benefit.

A tinge of extra patriotism to “Make in India” can lead to a sustainable partnership between domestic Rubber Processors and Indian Rubber Machinery Manufacturers for the future and boost the domestic economy further.

Make In India

Snap shot of article as it appeared in Rubber Asia Jan 2015 Special Edition

 

(This article by Prasanth Warrier first appeared in the Rubber Asia, IRE 2015 Special Edition) 


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