Tyre manufacturing is a complex technical process,
which, for the sake of simplicity can be broken down into eight
manufacturing stages:
Mixing
Various grades of natural and synthetic rubber are blended in an
internal mixer (commonly known as a Banbury) and mixed with carbon
black and other chemical products. This blend is called the "masterbatch"
and its make-up is carefully constructed according to the desired
performance parameters of the tyre.
Calendering
Textile fabric or steel cord is coated with a film of rubber on
both sides. Calendered textiles such as rayon, nylon and polyester
are used for the casing and the cap ply's. Steel cord is used for
the belts.
Tread and Sidewall Extrusion
The tread and sidewalls are constructed by forming two different
and specifically designed compounds into tread profiles by feeding
the rubber through an extruder. Extruders produce continuous lengths
of tread rubber which are then cooled and cut to specific lengths.
Bead Construction
The bead core is constructed by coating plated steel wires, which
are wound on a bead former by a given number of turns to provide
a specific diameter and strength for a particular tyre.
Tyre Building
Tyre building is traditionally a two-stage process. Although modern
tyre factories now use a certain number of single-stage building
machines, two-stage building is still widely used, particularly
for the more standard sizes. In the first stage, the innerliner,
the body ply's and the sidewalls are placed on a building drum.
The beads are positioned, the ply edges are turned around the
bead core and the sidewalls are simultaneously moved into position.
In the second tyre building stage, the tyre is shaped by inflation
with two belts, a cap ply and the tread being added. At the end
of this stage the tyre is now known as a "green tyre".
Curing
The green tyre is now placed in a mould inside a curing press and
cured for a specific length of time at a specific pressure and temperature.
The finished tyre is then ejected from the mould.
Trimming
Excess rubber is removed from the cured tyre on a trimming machine.
Inspection
Before the tyre is allowed to go to the despatch warehouse, it is
inspected both visually and electronically for quality and uniformity.
