Evolution of Mixing Mills

Evolution of Mixing Mills

By Anil Kumar Nair


Anil Kumar Nair, DGM Sales & Marketing, L&T Rubber Processing Machinery

The need to incorporate the various chemicals and fillers with rubber as the alchemists came up with their special brews of the ratio of these components, saw the humble 2 roll mixing mill as a very important machine and the fist use has been reported in 1830.
The rubber compounds found a plethora of usage and with each specific use, the complexity of the compounds grew. With the increase in popularity of automobiles and increased production, fine particle quantities and poisonous vulcanisers replaced traditional chemicals, thereby rendering open mill mixing hazardous. This necessitated internal mixers and the initial inventions of the internal mixers started making their appearance towards the later 1800.
There were two design approaches, one based upon a single-rotor masticator devised by Thomas Hancock in the early 19th century and a second based upon two non-intermeshing counter rotating rotors which were championed by Paul Pfleiderer. While both these designs existed and competed with each other in the market till 1920s, it was the uniqueness of the design by Fernley H Banbury and the Birmingham Iron Foundry (later Farell Birmingham) which formed the basis of the mixing paradigm
Fernley Hope Banbury was an English scientist and engineer who invented the Banbury mixer in 1916. Later in the 1950s and 1960s Pomini and Kobe Steel, commenced the manufacture of the Banbury mixers as Farell Birmingham licensees. Commencing with 2 wing rotors, which still finds use even today, the technology developed to the use of 4 wing rotors
Kobe Steel commenced innovations, after the expiry of the license agreement towards the late 1970s. To begin with the first 4 wing rotor was the 4WS, which was the four wing standard rotor. While this rotor found a wide usage, there were mixing quality related issues and subsequent analysis led to the discovery of the rotor geometry being directly responsible for this phenomenon.

Dispersion and distribution

It was proven in lab studies that the dispersion and distribution across the length of the rotors was not uniform and towards the short wings, at times, no dispersion was observed. These were the proverbial “dead spots”, where there existed no polymer-filler interaction. This was considering the higher dimension ratio of the short wing to the long wing, imparting a back pressure which prevented dispersion of the chemicals and filler. To overcome this, the mixing cycle had to be extended and also ram lifts were introduced to allow the batch to roll over.

As part of their innovations Kobe Steel worked on this ratio of small wing to large wing dimensions and the 4 wing Swirl rotor or the 4WH rotor was developed. This was suitable for both master batch as well as final batch mixing. This became the most selling rotor till early 2000

As part of further innovations and in view of the increasing demand of tough and dry compounds to suit radial tyre production, the 6WI rotor, a unique patented design of Kobe Steel limited was brought forth and till date remains the only successful 6 wing rotor commercially available.

Further to enhance the product portfolio, to aid mixing with silanization reaction, a rotor which had the capability to maintain a narrow temperature window over an extended period of time was developed. This was the 4 WN rotor.

India, though a big automotive market, did not have any KSL mixers till 2009. Traditionally KSL mixers were popular with Japanese manufacturers and the market was also confined to Japan China and Korea. The Americas were serviced through a 100% subsidiary KSBI, who operate out of Akron Ohio.

The large market consisting of Europe, South East Asia and South Asia had several mixing installations and was predominantly supplied by Farrell UK. HF and Pomini were the other players in this market, and recently all three have been consolidated under the HF brand

Larsen & Toubro Ltd was already a known name in these markets for the curing presses and hence both L & T and KSL decided to join hands to cater to this market and thus the 51:49 joint venture, LTKM was established in the year 2011. The commercial production started in 2012.

In the past five years, LTKM has supplied all the Indian majors either as part of the greenfield or replacing the existing mixers. Recently, LTKM has ventured into the field of mixer reconditioning also

One of the notable achievements of the last year was securing the mixer order for the first ever tyre factory in Bangladesh and these machines would be up and running towards the second half of this year. Globaly tyre market is expected to grow by close to 7% in 2017, but the factory utilization being low for most of the players, the translation of this demand to machinery requirement would be a good 6 months away

Year 2017 will see LTKM produce its 50th mixer, which would be an export machine and considering the projects which are on the anvil, LTKM is all set to make its name globally while carving out a special niche in the Indian market as it will be the only OEM offering reconditioning from India.


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