Before describing process performance, the production phases involved in the creation of a tyre are described here. There are two principal phases:
- production of the rubber compounds used in the various components of the tyre: tread, sidewalls, liner, bead filler, etc.;
- construction of the base structure, an actual rubber “framework” that supports all the components.
The rubber part of the tyre (tread, sides and fabric) is a special mix, more commonly referred to as a “compound,” which is mainly composed of rubber (both natural and synthetic), binders (mainly carbon black and silica) and plasticizers. Taken together, these components constitute about 90% of the compounds, while the remaining 10% or so is comprised of other components with specific functions such as, for example, accelerants, antioxidants, vulcanising agents, etc. The plasticizing components, the carbon black and the silica are stocked in dedicated silos and sent to a closed mixer (banbury), in which the compound undergoes its initial processing. A computer monitors and manages the quantity of ingredients coming from the silos. The lighter ingredients are instead pre-batched with specific control systems. In a second phase of mixing, special ingredients, such as vulcanising agents and accelerants, are added. The compound is then unloaded onto an open mixer consisting of two big rollers in order to complete its mixing and optimise its dispersion. Next, the compound sheet is plunged into a vat (batchoff) for cooling.
The prepared compound is then used to make the tyre tread and/or other tyre components. It is then extruded and assumes the appropriate form for subsequent processing. The heart of the tyre structure is represented by the fabrics, which are formed by longitudinal threads (weft) and may be comprised of various materials. The fabrics are then cut at a certain angle with respect to the longitudinal direction (the direction of movement, of rolling or of the weft). Other key parts of the tyre are the tread and the sidewall. The first of these performs critical functions, such as stopping on dry and wet surfaces. The second is the area close to the metal rim, which is called the “bead.” The base of the bead is supported by the ring, comprised of a series of steel wires, which stiffens the part touching the wheel rim. The semi-finished components described thus far (tread, beads, rubberised fabrics, sidewalls, etc.) must be assembled together to make the finished tyre, using “building machines”. The resulting tyre (called a “raw tyre”) is then sent to be vulcanised, which involves a genuine solid state chemical reaction. After being cooled, the vulcanised tyre is deburred to remove any imperfections that might alter its appearance. Then it is subjected to visual inspection (both internal and external) which is then followed – in the case of truck tyres – by X-ray inspection in specially shielded areas. The uniformity and balancing of the tyres are then checked.
PRODUCTION PROCESS OF A TYRE