Tire manufacturing
The tire is an assembly of numerous components that are built up on a drum and then cured in a press under heat and pressure.
Heat facilitates a polymerization reaction that crosslinks rubber monomers to create long elastic molecules.
The inner liner is a calendered[4] halobutyl rubber sheet compounded with additives that result in low air permeability.
The inner liner assures that the tire will hold high-pressure air inside, without an inner tube, minimizing diffusion through the rubber structure.
Sidewall extrusions are nonsymmetrical and provide a thick rubber area to enable molding of raised letters.
The apex provides a cushion between the rigid bead and the flexible inner liner and body ply assembly.
Belts give the tire strength and dent resistance while allowing it to remain flexible.
Mixing is the process of applying mechanical work to the ingredients in order to blend them into a homogeneous substance.
Internal mixers are often equipped with two counter-rotating rotors in a large housing that shear the rubber charge along with the additives.
The shearing action generates considerable heat, so both rotors and housing are water-cooled to maintain a temperature low enough to assure that vulcanization does not begin.
After mixing, the rubber charge is dropped into a chute and fed by an extruding screw into a roller die.
Components fall into three classes based on the manufacturing process: calendering, extrusion, and bead building is the same as the tire.
The calender is a set of multiple large-diameter rolls that squeeze rubber compounds into a thin sheet, usually of the order of 2 metres wide.
A creel room is a facility that houses hundreds of fabric or wire spools that are fed into the calender.
In the second stage of operation, the carcass of the tire is inflated, then the belt package and tread are applied.
Splices that are too heavy or non-symmetrical will generate defects in force variation, balance, or bulge parameters.
Pirelli Tire developed a special process called MIRS that uses robots to position and rotate the building drums under stations that apply the various components, usually via extrusion and strip winding methods.
This permits the equipment to build different tire sizes in consecutive operations without the need to change tooling or setups.
The bladder is filled with a recirculating heat transfer medium, such as steam, hot water, or inert gas.
In the final step, tires are inspected by human eyes for numerous visual defects such as incomplete mold fill, exposed cords, blisters, blemishes, and others.
