Making of a tyre: Apollo Plant visit
Published On 19-Sep-2019 19:10:13
An automobile comprises more than a thousand running components so as to perform flawlessly. While every component contributes in the working of an automobile in its own right, there are certain constituents which are more important than others. One such component that belongs to the former category is the tyre in an automobile. Think about it; if you can’t put a vehicle’s power down in an effective way, what is it good for? Or what’s the worth of those thousand-odd components for that matter?
Since pneumatic tyres form the backbone of a majority of private and commercial vehicles around the whole world, manufacturing one requires a series of complex and carefully thought out processes. To understand more about how a ‘normal’ tyre is manufactured, we had been invited to one of the most technologically advanced tyre manufacturing units in the country. The facility we talk about here belongs to Apollo tyres and is located at Orgadam in Chennai.
Before we move on and talk about the intriguing and complex manufacturing process that goes behind building a tyre, lets get acquainted to Apollo tyres first. Apollo is a homegrown tyre manufacturer which was established in 1972. Its first manufacturing unit came into action in 1976 at Perambra in Kerala. Over the last three decades, however, the firm has grown immensely in size as it currently has a strong presence in over 100 countries with manufacturing facilities across 3 continents- Asia (India), Africa (South Africa) and Europe (The Netherlands). Apollo in India currently holds the no.1 spot in commercial vehicle segment tyre sales, and stays at a strong third spot with 17 per cent market share (radial tyres) in the passenger vehicles segment.
[caption id="attachment_733" align="alignnone" width="960"] Apollo acquired Vredestein in 2009[/caption]
Apollo’s main brands comprise Apollo and Vredestein (acquired in 2009). While Apollo caters to passenger cars and commercial vehicles across different segments, Vredestein’s range of tyres are best suited for high-end luxury and performance vehicles. Apollo launched the premium Vredestein range in India last year. Apart from Vredestein, Apollo also owns Regal and Kaizen (truck-bus tyres), Maloya (passenger vehicles), Dura Tyres (retreaded tyres) and Dura Tread (retreading materials).
Talking about Apollo’s presence in the automobile OEM circles in India, the manufacturer is the official tyre supplier for OE manufacturers and its tyres come fitted as standard on cars such as the Volkswagen Polo, Vento; Skoda Rapid; Hyundai Elite i20, etc. The company will also be the OE supplier for the forthcoming new Toyota Innova (due for launch in late 2015 or early 2016).
[caption id="attachment_734" align="alignnone" width="1024"] Apollo'Chennai Plant has a production capacity of 500 metric tonnes/day[/caption]
Apollo’s manufacturing base at Chennai is claimed to be one of the most advanced tyre manufacturing plants in Asia. The Chennai unit specialises in radial tyres and runs at a daily capacity of 500 metric tonnes; translating to an average production of 16,000 tyres/day for passenger vehicle (PV) and 6,000 tyres for commercial vehicle (CV) segment. What’s more, the plant is currently undergoing an expansion, of which nearly 50 per cent is planned for CV segment. Apart from catering to the Indian market, the plant also manufactures winter tyres for European markets.
Our industrial visit at Apollo Chennai commenced with a brief overview of the facility followed by a video conference session with Mr. Satish Sharma, President, Asia-Pacific region, Apollo Tyres. During the interaction, he talked about the firm’s expansion plans, upcoming facilities, future projects, etc. Post this session, we were quickly relegated to the manufacturing unit since we had a lot to cover and grasp in a single day.
Once you step inside the tyre manufacturing unit, you are completely taken aback by the sheer size of the facility. However, as you learn more and more about each and every process that is being carried out during the manufacturing process here, you slowly tend to understand that beneath those massive machineries lie a phenomenal amount of proficient engineering skills and manufacturing prowess, which only a few others in the industry can manage to match. So without further ado, let’s step by step learn how rubber in its natural form is transformed into a circular shape that the world knows as a tyre.
[caption id="attachment_730" align="alignnone" width="1024"] Tyre manufacturing is a complex process[/caption]
Tyre manufacturing is divided into four major steps:
1. Compounding & Mixing:
A tyre as most people like to believe is not just made up of only rubber. Infact a typical tyre’s construction requires different varieties of rubber- natural or synthetic- along with carbon black, sulphur and oil as other additives. Depending on the usage, the composition of these compounds vary to achieve different objectives. However, even after doing so you can safely assume that more than 80 per cent of the total weight is contributed by rubber.
[caption id="attachment_727" align="alignnone" width="1024"] A raw tyre being transferred inside the manufacturing unit[/caption]
Normally, four major kinds of rubber are put in use during a tyre’s production, namely, natural rubber, styrene-butadiene rubber (SBR), polybutadiene rubber (BR), and butyl rubber (halogenated). If you were to distinguish these based on their functioning, the first three make the tread and sidewall compounds while the butyl rubber forms the inner liner that holds the compressed air inside the tyre, thanks to its low-permeable characteristics.
Rubber in its raw state, be it natural or synthetic, comes in a white latex form. However, the reason tyres, almost all, are black in color is due to the addition of a chemical called carbon black. In addition to that, specific chemicals like silica and sulphur are also mixed with rubber so as to provide different characteristics such as high friction (high grip) or high mileage (low friction) for a passenger car tyre. Other ingredients that are added during compounding and mixing of a tyre include anti-oxidants, anti-ozonants, and anti-aging agents.
In order to prepare a desired tyre compound, a mixing mill with two counter-rotating rollers is used. Pre-calculated amount of a particular compound is dropped off at the rollers where raw materials are mixed with each other at a temperature of approximately 120 degree Celsius. Once the mixing process is completed, the batch for a particular compound type is stored in form of continuous rubber sheets. It is then sent to the next processes like bead-wire assembly preparation, inner-liner calendering, steel/fabric belt/ply cord calendering, etc.
[caption id="attachment_729" align="alignnone" width="1024"] Steel Cords being processed[/caption]
2. Material Manufacturing Process:
Tyre material manufacturing includes three parallelly run processes that comprises building the carcass- body of the tyre; belt- to reinforce the carcass; the bead- that holds the tyre against the rim, and the tread- the part that comes in direct contact with the road.
The carcass & belt are produced by Calendering, i.e, coating the steel cords with rubber. This is done by incorporating a giant machine in place. The Calendering machine pulls strands of bronze-coated steel wires from a stack and mixes it into rubber compound at a uniform rate of 60 meters per minute. The freshly prepared carcass is subsequently cut according to the required size of the tyre using an automated cutting tool on flat bench.
[caption id="attachment_732" align="alignnone" width="1024"] A tyre in the making[/caption]
The next two processes are sidewall and tread preparation. Both the sidewall and the tread of a tyre are produced by a process called extrusion. A machine, referred to as an extruder, is used for this process. An extruder can be thought of as screw pump that heats the rubber compound and forces it out through a die. The one that Apollo uses in its manufacturing plant is capable of extruding 3 different compounds at a time- meaning 3 compounds can be mixed into one single compound for a desired spec-tyre. Post extruding, the compound is cooled off and then the tread or the sidewall is cut depending on the exact size of the tyre. Similarly, the bead in a tyre, which is made up of steel, is also rubber coated by extrusion process.
3. Tyre assembly (Green Tyre):
Once the tread, inner-liner, ply, sidewall, bead and belt are prepared, they are all sent in for the ‘assembly’. The assembly of tyre is done using a Tyre Building Machine (TBM) where all the components are sequentially assembled so as to form a raw tyre, also known as ‘green tyre’.
To give you a clearer view, a TBM is a giant horizontal roller drum. The raw or green tyre is assembled on it inside out, i.e., starting off with the inner-liner first and so on. So how does it work? The inner liner is wrapped over the roller, and then the body plies are applied. Both the components are then joined by bead on either side. The sidewall and tread are also added during the same phase. Once all the components are assembled, the TBM presses all of the components together, imparting the ‘assembled part’ a circular shape or tyre-like shape (see in the picture above for reference). The final product from this process, the green tyre, is then sent to the next process- Tyre Moulding.
[caption id="attachment_736" align="alignnone" width="1024"] 'Green tyre' being readied before moulding process[/caption]
4. Tyre Moulding:
Technically, moulding is the final step in the making of a tyre. During this process, the green tyre is cured, or vulcanized, by compression moulding process. This gives a tyre a road-worthy and functional shape. However, there’s more to it than just that. Moulding or curing of rubber also brings a number of chemical changes in the tyre that are crucial for its functioning.
[caption id="attachment_731" align="alignnone" width="1024"] Tyre curing[/caption]
The vulcanization of rubber makes it stiff and enormously resilient against external forces. The reason behind this is a phenomenon known as cross-linking is that it strengthens individual tyre components. For example, the sulphur mixed into the tyre compound cross-links with rubber molecules resulting in a hardened rubber with enhanced strength and improved elastic properties. Usually, for a passenger car tyre, the vulcanization time varies from 8 to 10 minutes.
So, how’s a tyre moulded into a final shape? The operator places green tyre inside the mould machine where the segments around the tread and sidewall are pushed inward by the curing press, providing the tread its outer shape. Simultaneously, a large rubber bladder (replicating an inner tube, albeit filled with high-pressure steam) inflates the tyre so that it fits snugly against the mould. Different tread-pattern tyres are produced using different mould design. Depending on the type of tyre to be produced, the moulds are replaced from time to time. At Apollo, they have over 160 different moulds to produce different tread-patterns.
During the moulding process, the manufacturer branding, marking, tyre size lettering etc., are engraved on the tyre sidewall as well.
[caption id="attachment_735" align="alignnone" width="1024"] Quality Check[/caption]
The final process includes inspecting the tyre visually for any defects. Post which, a tyre further undergoes a uniformity test where an automated machine checks balancing, concentricity, run-out, etc., of the tyre. Once through all that, the freshly prepared tyres are dispatched to various locations