The process begins with the mixing of basic rubbers with process oils, carbon black, pigments, antioxidants, accelerators and other additives, each of which contributes certain properties to the compound.
These ingredients are mixed in giant blenders called Banbury machines operating under tremendous heat and pressure. They blend the many ingredients together into a hot, black gummy compound that will be milled again and again.
2. The cooled rubber takes several forms. Most often it is processed into carefully identified slabs that will be transported to breakdown mills. These mills feed the rubber between massive pairs of rollers, over and over, feeding, mixing and blending to prepare the different compounds for the feed mills, where they are slit into strips and carried by conveyor belts to become sidewalls, treads or other parts of the tire.
Still another kind of rubber coats the fabric that will be used to make up the tire's body. The fabrics come in huge rolls, and they are as specialized and critical as the rubber blends. Many kinds of fabrics are used: polyester, rayon or nylon. Most of today's passenger tires have polyester cord bodies.
3. Another component, shaped like a hoop, is called a bead. It has high-tensile steel wire forming its backbone, which will fit against the vehicle's wheel rim. The strands are aligned into a ribbon coated with rubber for adhesion, then wound into loops that are then wrapped together to secure them until they are assembled with the rest of the tire.
Radial tires are built on one or two tire machines. The tire starts with a double layer of synthetic gum rubber called an innerliner that will seal in air and make the tire tubeless.
4. Next come two layers of ply fabric, the cords. Two strips called apexes stiffen the area just above the bead. Next, a pair of chafer strips is added, so called because they resist chafing from the wheel rim when mounted on a car.
The tire building machine pre-shapes radial tires into a form very close to their final dimension to make sure the many components are in proper position before the tire goes into the mold.
5. Now the tire builder adds the steel belts that resist punctures and hold the tread firmly against the road. The tread is the last part to go on the tire. After automatic rollers press all the parts firmly together, the radial tire, now called a green tire, is ready for inspection and curing.
6. The curing press is where tires get their final shape and tread pattern. Hot molds like giant waffle irons shape and vulcanize the tire. The molds are engraved with the tread pattern, the sidewall markings of the manufacturer and those required by law.
Tires are cured at over 300 degrees for 12 to 25 minutes, depending on their size. As the press swings open, the tires are popped from their molds onto a long conveyor that carries them to final finish and inspection.
7. If anything is wrong with the tire - if anything even seems to be wrong with the tire, even the slightest blemish - it is rejected. Some flaws are caught by an inspector's trained eyes and hands; others are found by specialized machines.
Inspection doesn't stop at the surface. Some tires are pulled from the production line and X-rayed to detect any hidden weaknesses or internal failures. In addition, quality control engineers regularly cut apart randomly chosen tires and study every detail of their construction that affects performance, ride or safety.
8. This is how all the parts come together: the tread and sidewall, supported by the body, and held to the wheel by the rubber-coated steel bead. But whatever the details, the basics are fundamentally the same: steel, fabric, rubber, and lots of work and care, design and engineering.
Vist the Goodyear website for more information.
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