Have you ever asked yourself one of the following questions: “What is in a tire?”, or “What is behind a tire?” - Making a tire is a very complex process. It starts from the selection and processing of raw materials, includes product design and development, initial tests, pre-production, the entire tire manufacturing process, vulcanization of the green tire plus quality checks and extensive performance testing. Yet, there is another question we should add: “What is a tire’s future?” – The answer to this question is closely linked to innovation. But let us start from the beginning.
Natural or synthetic rubber is the main raw material used in tire manufacturing. Natural rubber is obtained from latex, a milky liquid harvested form the bark of the rubber tree, Hevea Brasiliensis. To produce raw rubber, liquid latex is mixed to acids that make the rubber solid. Presses expel excess water and transform rubber into sheets that are dried, pressed into huge bales and then sent to the tire factories. Synthetic rubber, instead, is made of polymers from crude oil.
Rubber is stored in big warehouses, labeled and assigned for several tire production lines. The warehouse is operated on a first-in first-out basis in order to avoid that the rubber might lose its properties remaining stocked too long.
That being said, the growing global demand for rubber will reach 17 million tons by 2025 causing a shortage of this raw material. This is why we at BKT started to look for sustainable alternatives a long time ago. For the purpose of developing new compounding methods by using rubber obtained from the Russian Dandelion TKS as a renewable and sustainable alternative to natural rubber, BKT has entered into a joint research agreement with Kultevat Inc., a US company headquartered in Saint Louis, Missouri, specialized in green technologies. All studies and experiments have been carried out at BKT’s advanced Research & Development Center using stabilized TKS rubber for specific development testing.
No matter what kind of rubber is used, it must be treated with several chemical additives and then vulcanized. The additives used provide the tire with specific features: some of them, for instance, ensure resistance against fatigue, others protect against ageing due to UV or ozone exposition.
Another main ingredient is carbon black, one of the most common reinforcing fillers in rubber compounding, used in various formulations with different rubber types to enhance the mechanical properties of the polymer. It is a fine powder obtained from crude oil or natural gas combustion with a limited quantity of oxygen. The result is an incomplete combustion producing a large quantity of this pigment.
For major autonomy, BKT has set up a carbon black plant within our Bhuj production site, which enables increased quality control on both raw materials and finished products. As a carbon black manufacturer, we are also able to produce, and a greater variety of high-quality carbon black to be used for specific formulations during the compounding stage including customized carbon black of non-standard grades.
Product Design & Development
On the area of the Bhuj production site, there is an advanced R&D Center where solutions for the “tire of the future” are studied and developed. Designed for organizing all spaces from a completely functional viewpoint, the Research & Development Center includes the best range of equipment and software available on the market.
A team of engineers, chemists and technicians deal with anything related to the technological development of BKT products: starting from designing a new tire to creating new compounds for improved product performance including the implementation of new processes for an efficient and customized production of its top-of-the-range tires. Every year, BKT brings from 60 to 80 new products or new tire sizes to global markets.
The development of a new product requires a series of initial studies to define a tire’s main properties such as each component’s geometry, quantity, layout, compounds and dimensions. This decision basically depends on the type of application and specific operating conditions. To support this stage, a virtual three-dimensional prototype of the new tire is created, on which the effects of several strain such as mechanical stress are simulated. An FEA analyses, finite element method, on the virtual prototype enables engineers to simulate the performance of a pattern and other design elements such as bead and tire structure. Besides, the large variety of applications in the Off-Highway sector requires specific compounds. Also in this case, the FEA analysis supports the simulation of several compounds’ behavior. Studies on the virtual model are terminated when the applied changes are in line with the set target performance. This way, main construction and performance features are defined and a real prototype is built.
Afterwards a series of loop activities follows. These consist in the further fine tuning of performance features till the required specifications are reached. Every cycle starts with testing the prototype built during the previous stage following procedures that guarantee the highest quality standards. All test series provide data on the basis of which further analyses are carried out looking for additional changes and continuous adaptation of the tire features in order to improve performance. Each cycle ends with building a new modified and further enhanced prototype, so that the next cycle can start.
When the tested prototype complies with all performance requirements, the next stage is pre-production, and finally mass production.
The first step in the tire manufacturing process is compounding: natural or synthetic rubber, carbon black and other chemical substances and oils are introduced into a mixer that shall guarantee a compound’s homogeneity. During this stage, PC control systems measure and dose automatically each type of material required for the compound as to specifications.
Several compounds are used to build all tire components. The main elements and procedures are as follows:
- For tread and sidewall, the compound is extruded into the desired shape as to the specific part to be built.
- For tubeless tires (without air chamber), there is the inner liner that ensures the tire’s tightness, i.e. low air permeability. The inner liner is made of a specifically compound that is calendered in sheets and then cut to size.
- Besides, compounds are used to cover textile strips in a composite sandwich structure. These components called body ply are the tire’s bearing structure conferring it load capacity and resistance against impacts. Depending on the intended usage, the textile strips of the body ply can be replaced with steel wires so that the tire can sustain higher inflation pressure and heavier weights.
- Another type of components are belts, which are made of fabrics of different nature and coated with specific compounds. The belts are placed immediately under the tread influencing several performance features such as handling, driving comfort and the tire’s resistance against cut and wear, for instance.
- The beads of a tire are made by winding a steel wire into a ring, using a template with a diameter in proportion to the tire size.
All components are cut as to the dimensions of the specific tire.
The several components (body ply, belts, sidewall, beads, and tread) are assembled by means of latest-generation tire building machinery. According to the type, the tire building machine is composed of two or three rotating drums, on which the assembly operator places the components as to the established sequence. Exact positioning and orientation of components have been defined during the design stage and determine the tire performance features. Even though there are several types of machines and tires, basically component assembly is done in two separate stages. For less complex configurations, in the first stage the tire’s casing components are assembled, i.e. sidewalls, inner liners, beads, and body ply. During the second stage, the remaining components are assembled, i.e. belts and tread. As a result of these two stages, the so-called green tire has been shaped, which is ready for vulcanization.
The green tire is vulcanized within a mold that confers the tire’s final shape. A flexible air chamber called bladder is inflated at a set pressure value pushing the tire against the mold from inside. Simultaneously, the mold is heated to a set temperature. Process time, pressure values and temperature depend on the desired tire properties.
Finally, the tire is taken out of the mold for cooling. Afterwards all quality controls provided by our internal procedures are carried out. Each product is accurately inspected in order to spot any faults such as bubbles or holes within the rubber of tread and sidewalls as well as inside the tire. The tire is positioned on a testing rim, inflated and made spinning while sensors measure the tire balancing. Once inspected and tested, the tire is stocked in the warehouse and ready for shipment.
Quality Checks & Extensive Tire Performance Testing
Quality control starts with raw materials. It is mandatory for suppliers to provide complete and detailed documentation on raw material properties and composition. In addition, BKT performs its own tests on incoming raw materials upon arrival to verify and ensure their quality.
During the compounding process, rubber samples are collected and tested to confirm several properties such as tensile strength and density. Thanks to the attribution of unique codes and a comprehensive data recording system, plant managers are able to continuously trace each rubber batch and the specific components of every single tire.
When a new product is made for the first time, a small pre-series is created, from which the latest tires are submitted to testing: the tire is cut into sections to check if there are any air pockets among the layers, or pressed by metal grids in order to determine puncture resistance. Other important tests are tread wear resistance (basically a tire’s service life) as well as behavior at high speeds, since the latter lead to heat generation, which is a serious issue for a tire.
In addition, in-depth tire performance tests in dry and wet conditions are carried out on our modern testing ground. Each specialty tire has its own specific requirements in terms of load capacity, dimensional stability, cornering force, grip and traction – to name but a few. Timely and precise data and analyses are essential to ensure the best tire performance features tailored to your needs in addition to fuel economy and driving comfort that nobody wants to miss. This facility actually aims at continuous quality improvement, and the best adaptation to always more specific Off-Highway applications in any market segment.
These days there are many new trends in the entire automotive and specialty industries. We are researching into solutions to cope with sensor-assisted autonomous transportation, enhanced tire and equipment integration systems, data flow and analytics optimization for increased productivity, and so forth - all this in compliance with the megatrends in terms of sustainability, diverse mobility, electrification, and safety.
Being innovative as a company means that we do not wait for the formulation of new requirements. Yet, we are going to anticipate technological trends. For this reason, we are cooperating with universities and other research institutions as well as Original Equipment Manufacturers. We must be open and receptive for any technological trend and novelty.
As our head of R&D loves to say: “If tomorrow someone plans to develop vehicles to drive on the moon, we will be ready to join the project.”