Accurate inspection of tire sidewalls. (Process Machinery).

With tire specifications becoming tighter, the need for faster, more sophisticated and more accurate quality inspection for tire uniformity and appearance is critical.

Tires need to be inspected with greater accuracy, better throughput and higher sample rates using equipment that has less downtime. The sidewall inspection process must detect all suspect products while minimizing false rejects, involving costly, time-consuming hands-on inspection.

To meet these needs, tire manufacturers are challenging companies like Commercial Time Sharing, Inc. (CTI) of Akron, OH, and its parent company, Akron Special Machinery (ASpM), also of Akron, for on-line tire sidewall inspection solutions that can identify and measure deformities such as bulge, dents and depressions as small as one thousandth of an inch.

To meet such challenges, CTI partners with sensor manufacturers, such as LMI Technologies of Detroit, MI, for non-contact laser-based sensors. Sensor companies used by CTI often specialize in vertical industries and have experience in the integration process. Optocator sensors have been used in the rubber industry for two decades.

The Optocator 2201 is a relative distance measurement sensor that identifies tire deformities quickly and accurately within seconds and provides an X/Y plot of bulge, dents, depressions and the location of lettering on the sidewall. The Optocator can be modified and updated to meet new process demands.

Laser sensors are said to be superior to traditional contact/mechanical followers formerly used for tire applications, or even older capacitive sensors that provide outputs that change with each measurement. Unlike laser sensors, these other methods need a clear path on the tire to measure consistently. Letters and embossment on the sidewall severely reduce the repeatability of the measurement using these type sensors.

For tire uniformity machines, the Optocator has a sample rate of 16 kHz. Optocator sensors are not affected by surface texture, color, speed of different ambient light conditions that affect competitive units. The Optocator 2201 measures through black lettering, lube oil of other obstacles. The small spot size of 200 microns allows it to filter out high frequency signals and still detect and measure the low frequency bulge and dents.

Systems for sidewall inspection

CTI is a systems integration and software engineering firm specializing in multiple level manufacturing automation, from software programming to factory floor systems design, installation, implementation and training, to significantly increase productivity and improve profitability.

In the early 1990s, CTI received a contract to integrate its control technology into tire uniformity machines (TUOs) built by several companies, including Akron Special Machinery. As a result, they developed the TTOC (tire testing and optmization control) which replaces existing controllers on four-post tire test machines.

Recently, CTI acquired the exclusive marketing rights from Bridgestone/Firestone (BFS) to market their TSIS (tire sidewall inspection system) that was developed in 1987. BFS was one of the first tire manufacturers to use non-contact Optocator sensors for sidewall inspection in the early 1980s.

[FIGURE 1 OMITTED]

CTI's second generation TTOC II controller now integrates the TSIS system directly into the TTOC-II. Over the years, CTI has refined the TTOC and TSIS systems to improve cycle times, increase accuracy and reduce downtime. CTI's specialty is to strip an outdated TUO machine and completely rebuild and upgrade the control systems.

Continuous system improvement

TTOC-II and TSIS systems are continuously being improved to inspect higher proficiency tires and new sidewall styles. Test cycle time has been reduced to 17 seconds for a complete turnkey system.

Greater accuracy and quicker cycle times than traditional contact measurement and capacitive sensor systems used by competitors are said to be provided by the Optocator sensors. One competitor uses a microprocessor-based system that projects a 6.35 mm (0.25 in.) spot compared to a 0.02 mm (0.078 in.) spot for the Optocator. The larger spot affects the accuracy of the reading and limits the application. Another competitor uses CCD sensors that are said to be more difficult to use in a production environment and require additional cycle time to process extraneous data.

Sensors are key to the BFS system

The two Optocator sensors are said to be one of the key components to the TTOC-II/TSIS system. The Optocator sensors are mounted on opposing sides of an aluminum c-frame arm. The TTOC-II/TSIS monitors the signals from the Optocators and identifies the type of depression, how wide it is at the base. the dimensions of its slopes and other such geometrics. Four thousand readings are made of each profile, with the tire spinning at 60 revolutions per second. Up to five profiles can be made during the standard uniformity test.

The Optocator 2201 is being enhanced with a high frequency data acquisition system that will increase the speed of the sensor to a 32 kHz sample rate and 8 kHz band width.

The sensor has gone from a 1 kHz to a 2 kHz and currently a 4 kHz system. it has also gone from a 16 kHz sample rate per second to a sample rate of 32,000 samples per second.

Tire manufacturers favor sensors

One manufacturer has competing systems within the plant, as well as a TTOC-II/TSIS system. The manufacturer puts all tires rejected by competing systems through the TTOC-II/ TSIS system, and has found that two out of every three tires rejected by the competing systems are not defective. Rejected tires could have cost the manufacturer thousands of dollars, plus hundreds of man-hours in testing.

Additionally, to service the TTOC II/TSIS systems, CTI can access the systems over the internet.