Wave Issue 0108 2/8/01 Article 2-01

***Tire Inspection and the Technology Involved
by Amanda Rogos
(February 5)

The hype has calmed down now, but for quite some time
Bridgestone/Firestone was receiving a lot of unwanted attention
due to an August 2000 recall of 6.5 million tires. Since that
time, the tires, specifically ones manufactured for light trucks
and sport utility vehicles, have been implicated in an estimated
174 deaths - some dating as far back as 1992, according to
Federal auto-safety regulators. The National Highway Traffic
Safety Administration reported this week, that since its update
in December, it has received 1,700 new complaints alleging tread
separations, blowouts and other problems involving Firestone
tires.

The recall was due to "belt separation," and because of our love
for technology, the WAVE Report investigated the issue – and what
is being done to avoid these incidents in the future.
Specifically, belt separation occurs when centrifugal force pulls
at the steel belts within the tire causing them to go out of
shape, which can eventually lead to a separation at the edge of
the belts. If this spreads, the tire can eventually come apart,
which is what the Firestone tires had done.

Most of the initial accidents reported came from Texas and
Southwestern states with warmer climates, and therefore initially
the recall was claimed to be due to poor inflation and heat
damage. Heat can affect the way a tire tread bonds the rest of
the tire, and has been associated with an increased rate of tread
separation. Complaints alleged that Firestone tires had peeled
off their casings, sometimes while the vehicles, usually light
trucks or SUVs, were traveling at high speeds. Some drivers said
their vehicles rolled over or skidded out of control. In some
cases, the tread wrapped itself around the rear axle, causing a
wheel lockup.

Eventually the recall spread nationwide and in January of 2001,
Bridgestone/Firestone released a report detailing the cause of
the tire malfunctions. The company listed four major causes,
which included

(1) design problems in the tire's shoulder, the area where the
tread meets the sidewall, which can lead to cracking and belt
detachment;

(2) a defective rubber processing procedure at B/F's plant in
Decatur, Illinois which caused a lower level of belt adhesion
than the procedures used in other company plants;

(3) customer misuse through punctures, improper repairs and
severe impacts; and

(4) the inflation recommendation by Ford which at 26 pounds per
square inch, was lower than the manufacturer's suggestion.

We were more interested in the technology that would prevent
another such catastrophe, so we began researching the tire
market, manufacturing and inspection. Just for some background -
according to the Rubber Manufacturers Association, there were 822
million tires on American non-commercial vehicles in 1999 and 316
million tires shipped throughout the industry. Market estimates
for the year 2000 include (units shipped) 61.6 million passenger
car tires, 7.5 million light truck tires and 1.1 million
medium/wide base truck tires.

The tire manufacturing industry is an involved process. In fact,
Charles Gilmore, President and CEO of Yxlon, an x-ray inspection
technology manufacturer claims that, "The tire is the most
sophisticated component on an automobile." Tires are built in
batches, not assembly lines and the manufacturer's are quite
secretive about their processes and production.

The first step is the computer specifications and the development
of the prototype tire. The first set of inspection techniques are
done at this step, to ensure a proper design. Holography and
shearography are the inspection techniques used.

Both technologies form a comparison between a "standard" body and
a body after change. In holography a hologram of the object is
recorded, then the tire is subjected to different levels of
temperature, pressure and vibration to compare the difference in
the holograms.

Shearography involves the same kind of process using lasers and a
digital camera. According to Eugene Shaw, President of L-RAY, a
company that designs and manufactures digital video shearography
systems, film holography and shearography are not well suited for
online testing, which is why they are used in the beginning of
the manufacturing process. Digital shearography, a new, cost
effective and high-speed method of testing tires, is being
developed, that can be used on the completed and cured tire. L-
RAY estimates that their first production model will be available
in about 4 months. Shaw expects, "the tire testing industry to
flourish in the coming years because of increased awareness of
safety and liability issues…" Companies using shearography
include Goodyear and Bridgestone. Even NASA has used it for
testing on components of the Discovery space shuttle.

After the prototype tire is approved, the proper materials are
chosen (rubber, oils, pigments and additives) and combined and
the tire processing begins to create the sidewall, tread and
other parts of the tire. The assembly process works to develop
the inner liner, body plies/belts, hoops of wire and the sidewall
to create an uncured, or green tire. This is placed into a mold
and inflated, forming the tread. At this point, the final
inspection takes place either manually or using x-ray technology.

One hundred percent of large tires are x-rayed at the end of
production, and if defects are found, there is a chance that
tires can be reworked and sold anyway, at a lesser grade. Light
truck and passenger car plants use random sampling for their x-
ray inspections and when defects are found there is no attempt at
repair.

Surprisingly enough, there are a very small number of defects at
this point in the process. In fact Charles Gilmore estimates that
rejection levels are below 0.5%. According to Dr. Jon S.
Gerhardt, Adjunct Design Associate Professor at the University of
Akron, most of these defects are visual in nature, such as a
botched logo or serial number – so the design defects, are much
lower than 0.5%.

Gilmore's Yxlon International is a company that produces
industrial x-ray solutions for several industries, and is a
leader in machines for non-destructive testing. Their systems are
used to detect broken and crossed body ply cords, the strands of
fabric forming the layers of the tire; material voids; and
something called belt step-off, the difference in width between
two belts, if the belts are centered, when more than one belt is
present within a tire. Their systems are physically large and
cost between $300,000 and $1 million. Also included is a PC,
based on dual or quad Pentium 700MHz processors with sufficient
memory capacity to handle images between 25-60MB in size.

Yxlon's newest product is an automated x-ray system, called AXIS,
which is, in fact, a machine vision system for tire inspection.
Automated systems will eliminate the need for the operator that
interprets the x-ray image, therefore, according to Gilmore,
reducing the inspection labor from 24 hours in a 24-hour period
to 2.5-5 hours in the same period. It will also reduce rejection
levels to 0.1% in situations where human operators typically
reject 0.5% of production. In a plant building 6,000 tires per
day for a $300 truck tire, this would result in a $630,000
savings per year.

In summary, although there has been an increased interest in
these inspection technologies and tire safety, the companies we
talked with admitted that these techniques would not have found
the defects apparent in Bridgestone/Firestone tires. The recall
was due to a separation in a rubber belt, which could not have
been seen in digital images, holograms or x-ray images. There has
been, however an increased awareness of safety in the industry
and that includes the products that ensure safety measures. Tom
Kane, Head of the North American Office for Collmann, another x-
ray manufacturer, predicts an increased usage of x-ray systems in
the market due to this awareness. He suggests that most tire
manufacturers already have these systems in use, and will
increase their usage from a random sampling, in order to reduce
their liability. Due to the system's cost and longevity, plants
will not purchase more of them, just increase their usage.

Nevertheless, we felt much safer after learning how much care and
technology is put to use in each and every tire manufacturing
plant.

**A complete tire manufacturing diagram is available online at: