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Know The Structure of A Mechanical Bladder Curing Press

Curing is the process of applying pressure to the green tyre in a mould. This gives it its final shape. There is heat energy applied to stimulate a chemical reaction between the rubber compounds and other materials.

In curing process, you will observe (a video) that the green tyre is transferred onto the lower mold bead seat, a rubber bladder is inserted into the green tire, and the mold closes while the bladder inflates. As the mold closes and is locked the bladder pressure increases so as to make the green tire flow into the mold, taking on the tread pattern and sidewall lettering engraved into the mold.

The bladder is filled with a circulating heat transfer medium (such as steam, hot water, or inert gas). At the end of cure the pressure is bled down, the mold opened, and the tire stripped out of the mold.

Various suppliers manufacture curing bladders to fit to the different curing press types viz. Bag-o-Matic (BOM), Autoform and Hydraulic (Bagwell).

A bladder curing press cure bladders. Sizes vary because there are radial and bias type curing bladders for the passenger car, light truck, OTR (Off-The-Road), agricultural, bicycle, and motorcycle tyres. You will also find curing bladders for tire retreading and air spring production.

Here’s a structure of a compact mechanical bladder curing press.

Know A Bladder Curing Press

Additionally, you would also find this L&T newsletter informative on technical aspects.

A good curing bladder has following key features

  • It is made of a sustainable and flexible compound
  • The bladder contour is optimized to tire contour
  • A good surface structure to prevent trapped air
  • Durable and simple to use during service

If the bladder contour and venting system are not optimized, the tyre plants experience higher level of trapped air and blisters. This is predominant in motorcycle tyres when compared to other tyre segments.

A good bladder has minimum inner-liner consumption. It also facilitates a smooth and simple final inspection of the tyre due to its constant surface structure. Imperfections, if any, can be easily detected  which in turn gives you extra ordinary final finish.

So choose your bladder curing press wisely and operate it smartly to produce the best curing bladder for your customers.

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One Must Dare To Dream – R.V.Gandhi

One must dare to dream. Entrepreneurship is about dreaming and conceptualising, says R.V.Gandhi, Managing Director and chief promoter of GRP Ltd in an exclusive interview with Rubber & Tyre Machinery World.

“Great leaders don’t set out to be a leader. They set out to make a difference. It’s never about the role – always about the goal.” 

The above verse best summarizes Rajendra V. Gandhi (RVG). From building an ethical corporate organization in GRP, to serving on prestigious boards and industry bodies, public and private trusts that serve the cause of education in rubber, women empowerment, training in ethical values, water resource management, Gandhi’s immense contribution to Indian rubber industry has established him as an inspirational business leader and an iconic corporate citizen.

While the global reclaim industry depended on the European technology for manufacturing, Gandhi boldly decided to design, fabricate and install an entire plant and machinery for the manufacture of Reclaim Rubber, with complete indigenous components when India was largely deprived of foreign funds for imported machinery. This pioneering effort, at the start of his career as a young graduate engineer from IIT-Mumbai, ensured the beginning of a reclaim movement in India. Under Gandhi’s leadership, GRP Ltd has emerged as one of the largest manufacturer of reclaim rubber in the world, setting benchmarks for others to follow. Its an honour to know him and present you his leadership wisdom in this edition.


Click cover to read online

I urge you not to miss reading this complete interview online on our digital edition (or please click on the image above). You will immensely gain from his wisdom shared through passionate narration of personal experiences of over 40 years; know his views on changes, new ideas energizing the reclaim rubber industry, sustainability, challenges, expectations from equipment manufacturers, and machinery selection advice for buyers.

Here’s one teaser Q&A below, while the full interview has 10 questions.

Q) Reclaim Rubber is widely used in manufacturing of automobile tyres and tubes as well as many other rubber products. How do you ensure that industry acknowledges the ‘sustainability & environment friendly’ aspect of Reclaim Rubber and consciously increase its usage in their products; especially when there are favourable price fluctuations for them in NR and SR?

RVG: In the aftermath of the World War II, Reclaim Rubber emerged as a significant player in countries like USA to offer the third source of rubber hydro carbon after Natural Rubber and Synthetic Rubber. But with advent of cheap crude oil prices in the 50’s and 60’s, and huge production of Synthetic Rubber saw demise of Reclaim Rubber Industry in the western world. By late 70’s barring one or two Reclaim Rubber producers almost all manufacturers ceased to exist in USA / Europe.

As a result, almost one generation of rubber technologists did not have the knowledge of use/advantages of reclaim rubber in compounding.

Consequently, when our Company in early 90s decided to enter export market we realized, we had to re-educate technical people in the compounding division of our customers to see the benefit of Reclaim Rubber as a technically sound ingredient / raw material rather than cheap inexpensive filler. It took a lot of time and efforts to build trust with our customers.

After 2005, with the Chinese economy galloping at more than 10% annually, there was a concern worldwide about possible shortage of Natural and Synthetic Rubber. The prices of Natural and Synthetic Rubber along with crude oil price began to rise rapidly. In addition, with the adverse effect of global warming, several Governments became conscious about sustainability and environmental degradation.

GRP since then has been highlighting the role of Reclaim Rubber from the point of view of sustainability and as a environmental friendly raw material. We have succeeded to some extent in this endeavour.

In recent times, however with the crash in the commodity prices as well as in the prices of Natural and Synthetic Rubber, there are fewer incentives for using more Reclaim Rubber despite of it being more environment friendly raw material.


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Also, the center fold of this issue ‘One Page Leadership Insights from Around the World’ should be an added resource for you, I trust.

Centre Page Preview

Do review page 25 of the eEdition

I look forward to your feedback and thoughts of this interview.

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Anatomy of a Bale Ply Reel Winder

Have you heard of Bale Ply Reel Winder Machine?

Most likely a YES! if you are in the tyre industry.

For the benefit of other starters, this is an allied equipment. Used as a conveying and winding system in tire industry, a Bale Ply Reel Winder consists of two stations for winding up fabric lined rubber sheets.

The winding system receives fabric sandwiched Rubber Ply from your calendar and is wound in a reel at a wind-up speed of 16-32 rpm. The conveying speed is around 40 meters/minute.

Structurally, this machinery consists of four key components.

  1. Wind-Up Conveyor
  2. Ball Screw Assembly
  3. Frame Slide Assembly
  4. Reel Lift Assembly

Below is the equipment information image card on the Anatomy of a Bale Ply Reel Winder (for your quick preview) with inputs from L&T Rubber Processing Machinery.

Bale Reel Winder Image Card

For additional details, I urge you to also check out L&T’s newsletter which is fairly informative on operational aspects and technical specifications along with pictures of this machinery.

Do you want one for your Plant today? Or do you find a compatible use of Bale Ply Reel Winder (with customization) elsewhere for conveying and winding requirements in your operation.

Let us know your thoughts.

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13 Things You Should Know About Hydraulic Power Pack

If you have seen or used an Internal Mixer, Bale Cutter, Press, or any Hydraulic machinery then you have witnessed a Hydraulic Power Pack in operation.


Here are 13 things you should know about Hydraulic Power Pack.

  1. By definition, hydraulic power packs are self-contained power-units used instead of a built-in power supply, to transmit power from one location to another and thus run your rubber machinery. A hydraulic system employs enclosed fluid to transfer energy from one source to another, and subsequently create rotary motion, linear motion, or force.
  2. Hydraulic power packs come in different shapes and sizes; some are very large and stationary whereas others are smaller and compact. The mechanical characteristics and specifications of a hydraulic power pack dictate the type of applications for which it can be effective.
  3. You can identify hydraulic power packs through its main components. Because irrespective of the size of the unit, all power packs will have the following;
  • A hydraulic reservoir (or tank) which holds the enclosed oil. This is a storage unit designed with enough volume for the oil in the pipes to drain into it. They also ensure this oil is stored and maintained in the best possible condition. Reservoirs will come in different sizes. Common auxiliaries for a reservoir include filler/breathers and drain ports, level gauge, level switches and inspection covers.
  • Regulators that control and maintain the amount of pressure that the hydraulic power pack delivers. These are very vital.
  • Pressure Supply lines and Relief lines. The supply line supplies fluid under pressure to the pump and the relief lines relieve pressure between the pump and the valves. The relief lines also control the direction of flow through the system.
  • Motor to power a pump
  • A pump to perform two actions. Firstly, it creates a vacuum at the pump inlet and with the help of atmospheric pressure, forces fluid from the reservoir into the inlet line. This fluid is then fed to the pump. The pump then delivers this fluid to the pump outlet and force feeds it into the hydraulic system.
  1. Some of the important factors that influence a hydraulic power unit’s performance are pressure limits, power capacity, and reservoir volume. In addition, its physical characteristics including size, power supply, and pumping strength are also significant considerations. Reputed suppliers take great care to ensure that a large, durable hydraulic power unit is built for functioning under a range of environmental conditions.
  2. Hydraulic power packs have other components like
  • Filters: Filtration is a critical part of a hydraulic power pack, ensuring wear is minimised and efficiencies are maintained. Basic suction strainers do not allow large contaminants to enter the pump. Pressure filters are normally configured at the pump outlet and ensure only filtered oil enters the hydraulic system. Contamination within the system is filtered out by the return filter before it enters the hydraulic reservoir.
  • Pressure Control valves that limit or control the hydraulic pressure within the hydraulic system.
  • Directional Control hydraulic valves (manual, electrical, pneumatic or hydraulic operated) direct the oil flow around the system to operate actuators, motors or other functions.
  • Cooling is another other key consideration, where efficiencies within a system or machine will produce heat in the oil; this must be cooled to ensure long life and high-efficiency.
  • Accumulators: These are containers that can be attached to the hydraulic actuators. They collect oil from the pump and are intended to build and maintain fluid pressure to supplement the motor pumping system.
  • Coolers and Heaters: As part of the temperature regulation process, an air cooler can be installed near or behind the filter unit to prevent temperatures from rising above operational parameters. Likewise, a heating system, such as an oil-based heater, can be used to elevate temperatures when necessary.
  • Power Unit Controllers: The hydraulic controller unit is the operator interface containing power switches, displays, and monitoring features. It is necessary for installing and integrating a power unit into a hydraulic systems, and can usually be found wired into the power unit. Oil level and temperature protection switch, Pressure switches and filter clogging switches are quite common.


  1. Hydraulic power packs come with a variety of valve connections. This means that you can power a variety of rubber and tyre machinery by using the appropriate valves. Most manufacturers segregate their models into a ‘standard’, ‘mini’, ‘micro’ or‘bespoke’ power pack categories.
  2. When picking a hydraulic power pack there are a variety of pumps and options to pick from. Hence, it is important to pick the right power pack to meet your machines needs. It is also important to consider a power pack that will help maximise productivity and minimise cost.
  3. In rubber and tyre machinery, you would need custom design of your hydraulic power packs depending on the features you select and how you select. For example, you could either opt for a single power pack for your drop door and hydraulic ram operations of a mixer; or choose separate power packs for individual operations depending on the circumstances at your plant.
  4. Your supplier should review the pressure and flow data together with you. And they should also take load profiles and the thermal budget into account. Doing this ensures that you get a power pack that precisely meets your technical requirements and operates economically.
  5. It is ideal if you or your machinery supplier get everything integrated from a single source. Because, fewer interfaces means your hydraulic system gets built faster. Your costs are lower, too.
  6. Experts recommend use of high-efficiency low-noise internal gear pumps when designing power packs. Your supplier may consider accumulator charging technology or variable speed drives as may be the case for your application. Multiple pressure circuits are another option.
  7. Hydraulic power packs require regular maintenance to ensure they work properly and safely for extended periods of use. Maintaining hydraulic power packs is relatively simple. You should check the tubing for any noticeable problems such as dents or cracks. You should also inspect the reservoir to check for any corrosion or rust. And do regularly change the hydraulic fluid as per recommended maintenance schedule of your hydraulic power pack.
  8. Hydraulic power packs must be installed and mounted in a clean and dry location void of any standing water or accumulated run-off.

Summarizing, you should opt for a power pack that has low power consumption, requires very little installation space, and operates with low cooling requirements. This would mean that your operating costs are very low for the unit and it’s easy to integrate into your main machinery. All of these would help you procure power packs featuring high reliability and availability on the one hand, and easy and cost-effective integration into your rubber machinery on the other.

Did I miss some aspects?  Would you like to add more to this list? Let us know.

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What Is Vulcanization? 5 Amazing Videos You Must See

Vulcanization of rubber is a process of improvement of the rubber elasticity and strength by heating it in the presence of sulphur. I touched upon vulcanization in our earlier posts on Autoclave and Rotocure.

A quick glance at Wikipedia will tell you that although vulcanization is a 19th-century invention, the history of rubber cured by other means goes back to prehistoric times. Thomas Hancock (1786–1865), a scientist and engineer, was the first to patent vulcanization of rubber. He was awarded a British patent on May 21, 1844. Three weeks later, on June 15, 1844, Charles Goodyear was awarded a patent in the United States.

While a picture is worth thousand words, logically a video is worth much more. Hence today I choose to concisely share with you over 1 million words in 5 amazing videos on vulcanization.

The first video of 4.49 mins is an ideal start if you are trying to get your basics right on vulcanization process and gives you a text book approach. (Caution: The slow speed and tone can be unnerving to some of you!)

Vulcanization Video 1

The next one is a more professionally made one from ‘How Stuff Works?’ and expands the concepts of vulcanization further. This video is concise and 2.10 mins long.


The third video (3.39 mins) shows an application in the form of Rubber O-Ring Vulcanization Bonding.

Rubber O-Ring Vulcanization Bonding Video

Speaking of Curing and Vulcanization in rubber, it is pertinent to mention tyres. The next video is 5.17 mins long on ‘How are bicycle tyres made?’ and the application of vulcanization is just a small part of this whole process. However, it gives you the perspective to position rubber vulcanization rightly in the product manufacturing process.


With technology advancements, conventional methods are being replaced with more energy efficient and productive solutions. It is in this context, you may see the next video of a Rubber  Profile Curing Vulcanizing Line. The 1.33 min video by Deguma shows a CV-line consisting of a UHF microwave channel, a hot-air channel and a infrared channel.


Did you find the fourth video of bicycle tyre above curious to explore more? Or are you a bicycling fan? Then here is a sixth video as bonus for you. Well-paced, detailed and professionally made, I found this 10.56 min video of a modern bicycle tyre and tube manufacturing from Schwalbe interesting. (Note: I am not making any brand recommendation here. However, the video is worth a watch.)

Bicycle Tyre and Tube Video

You would have spent a little less than 19 minutes if you have watched all the 5 videos on vulcanization in full. Were they knowledge-enhancing? Let me know your thoughts.

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VMI iCOM – A New Alternative to Final Rubber Mixing I Learnt At RUBBERCON 2015 Chennai

The rescheduled edition of RUBBERCON 2015, held on March 1-3, 2016 at Chennai was well-organized by IRI (Indian Rubber Institute) and IRCO (International Rubber Conference Organization).

Personally, this has been one of the best attended, well-organized and amongst biggest conferences I have been to recently. And to most delegates, this has been a different experience altogether.

Kudos to the complete team of organizing committee and supporting members for their massive efforts and time invested to make this conference a success. Because of them, I think RUBBERCON 2015 Chennai would easily occupy its unique place of prominence amongst biggest international conferences.

Over 75 speakers from 19 countries presented papers.

I was fortunate to successfully attend all my shortlisted speakers.

In an earlier post on mixing, I had mentioned that Single-stage mixing is not always cheaper and two-stage mixing is not always better. So, when my good friend, Dirk G.H. Reurslag, Sales Director (Industrial Solutions) of VMI Group (innovative leaders in rubber and tyre machinery) presented a new alternative on Continuous Final Mixing, it caught my attention quickly.

If you are looking to operate the complete mixing line by a single person, then you will find this JIT (Just in Time) approach to continuous mixing and blending of final rubber compounds interesting.

Before you get excited and review it’s long list of advantages, let me brief you the basic concept.

Basic Concept:

At its heart, this “mixing approach” has a cold-feed extruder along with the gear pump and they are controlled by software. VMI calls it iCOM®.

Sound’s simple (Right?)…. Wait. There’s more to it.

VMI Continuous final mixing

VMI Continuous Final Mixing Line

Operating Principle:

If you are seeking continuous proportional blending, you will know that proper distribution-mixing should take in the screw extruder.  And for final mixing, you require the screw extruder to properly incorporate the chemicals into the compound mix. Hence, the mixing screw design from VMI is advanced and unique.

The software used is equally sophisticated to control the speeds of the screw, the pump (and input pressure) and the volumetrically operated loss-in-weight feeding system.  The mixing and proportional blending uses

  1. the volumetric operating principle of the gear pump (Read our earlier post on the concept of gear pump working) and
  2. the abilities of homogeneous plasticizing of the rubber by the screw type extruder.

The special screw extruders are the VMI SHARK® extruder gear pump combinations. Different screw types are available. VMI recommends that they select a screw for you depending on your specific application.

The chemicals to be mixed are usually polymer bound, pre-dispersed, in the form of granules and are fed to the mixing extruder by an accurate volumetrically operated loss-in-weight feeding system.

Image - VMI

Proportional Blending (L) & Continuous Final Mixing (R)

For Proportional Blending, you require another side-feeding extruder gear-pump. The function of the screw of this side feeding extruder is not to mix. Rather, it only needs to properly plasticize the rubber and feed it (free of entrapped air) to the gear pump. The gear pump, in its turn, pumps the rubber compound into main mixing extruder in a volumetrically controlled fashion.

Continuous Final Mixing:  You can adopt this volumetric controlled mixing-extrusion in combination with accurate dosing of granules (that contains vulcanizing agent and accelerators) by a loss-in-weight feeder, to do continuous mixing.

Controlled Back and Forward Blending:  This is the third type of blending you could achieve in the extruder screw and barrel combination. This ‘compensates’ for little irregularities, if they might occur, in the loss in weight feeding of your polymer bound chemicals

VMI develops new concepts and innovative uses of technology with the end-user. VMI seeks to work with clients that will become launch users and close collaborators. In this way, VMI only ever takes to market concepts that have been tested under real-world conditions and proven to deliver competitive advantage.

Emphasizes Dirk Reurslag, “iCOM® solution is the more economical alternative to mixing in an internal mixer”

VMI worked out the iCOM® final mixing process, which includes the VMI SHARK continuous mixing solution in combination with Rhein Chemie’s  Rhenogran polymer bound chemicals and Rhein Chemie’s Rhenowave in-line analytics.


Your advantages of VMI iCOM® for final mixing are

  1. Lower investment on a final mix line delivering faster ROI and time to profit.
  2. Compact, integrated solution occupying modest footprint.
  3. Lower energy consumption as compared to the use of an internal mixer based final mixing line.
  4. No electricity consumption peaks like in the case of an internal mixer. Hence, a sustainable solution that reduces energy use and improves profit potential.
  5. Decentralized final mixing: This means Just in Time production as it reduces costly transport requirements for final batches. This reduces your stock of compounds and simplifies your logistics.
  6. Just in time (decentralized) final mixing allows more ‘rapid’ vulcanizers, resulting in shorter vulcanizing time.
  7. The proportional blending capabilities gives you various kinds of possibilities – Cross Blending (Most of you in mixing would know it well. This is referred to as just blending from two stage mixing), Controlled back and forward blending or Proportional Blending (both mentioned earlier.)
  8. No ‘fading’ in the produced strip: no difference in heat treatment: With batch production the first part of the (long) strip was shorter on the mill than the last part.
  9. Consistent quality of final mix compound with no scrap or rejects.
  10. One Energy Cycle (Heat-up, Cool-down cycle) can be avoided by combining final mixing with first extrusion step.
  11. Straining in the iCOM® line is possible
  12. Degassing in the iCOM® line is possible
  13. Affordable for even smaller companies

And just in case you thought this is an entirely new concept, you are in for a surprise. A Belgian compound manufacturer has the VMI iCOM® production line installed and successfully working since 2012.

VMI Group’s leadership in Extruder-Gear Pump solutions is renowned. They specialize in designing and engineering superior customized machinery for the rubber and tyre industry.

When I visited their stall at RUBBERCON 2015, I also learnt something new in their souvenir they were gifting to their customers. Known as Klomp, (more interesting facts here – Clogs), they are a type of footwear made in part or completely from wood. Pair of these is known as Klompen.

If you had been to their stall, did you pick up Klomp or Klompen (Single or Pair)?


Summarizing, if you are looking for an innovative, automatic, decentralized, Just-In-Time, final rubber mixing line without internal mixers, this new alternative in VMI iCOM® I learnt at RUBBERCON 2015 Chennai is worth your evaluation. I am also informed, it further enables production of customized, creative and precisely targeted compounds.             

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Rubber Extruders And Extrusion – Special Supplement

Rubber industry only had Hot Feed Extruders until 1950’s. Then came the Cold Feed Extruders and other variations as we see them today.

Rubber extruders have a varied field of application. So, when you come across a rubber profile, strip, hose, cable, wire, cord coating, tire tread, v-belt, tube, or blank remember that they are only a few handful of products manufactured using extrusion process.

Life today is mostly spent trying to catch up with latest developments. However, in the process the basics and fundamentals are sometimes overlooked. So, in this Knowledge On-The-Go Special Supplement, we bring to you a ‘collector’s edition’ on Extruders and Extrusion incorporating the fundamentals.

(Our digital editions are available on two platforms – Youblisher or Yumpu)

Extruders_Special Supplement

Click on the Image to Flip Through The Digital Book

Download PDF Here

I hope you find this special supplement informative.

(Disclaimer: All the pictures and statements in this special supplement are sourced from web or shared by respective companies. All copyrights belong to actual owner. Rubber Machinery World does not independently verify them nor will vouch for their genuineness, hence will not be liable for any misrepresented data. The images are used here for representation purpose only.)

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If you are an equipment supplier and would like your organization to be promoted on Rubber & Tyre Machinery World, please see the opportunities on Partner Me or Contact Me at for your customized offering.