Poling Group News   |   Volume 5  |   Issue 2
Improving Operational Performance
TU Tune-up: Getting the Most From Your Tire Uniformity Machines

A Tire Uniformity machine is a complex piece of equipment. Precise air regulation, exacting loadwheel positioning, and dead-center spindle rotation all combine in a choreographed sequence of moves to measure the forces of a single tire, one by one, every 20 seconds.

Driven at this level of performance day after day-year after year-these machines inevitably show a reduction in productivity and capability evidenced by:

• An inflation system that does not perform as fast as it once did
• A loadwheel that shows signs of wear
• Rims that can no longer be perfectly centered on the spindle

To help our customers address these productivity and capability issues, CTI engineers focused their efforts on developing an economical suite of products for retrofitting to existing Poling Group machines. CTI’s new combination of hardware and software not only increases machine productivity, it also brings older, non-conforming machines back into specification at an investment that provides significant savings over a ‘total rebuild’ approach.

Read on to see the machine areas that will benefit the most from a tune-up.

Data Acquisition

The most important step in any controls upgrade is to modernize the equipment, and aging data acquisition systems are no exception. These systems, currently populated with old electronic parts and designed with old paradigms, were once the mainstay of tire test machines. But with consumers and corporations increasingly demanding tighter specifications on tire testing, old electronics have failed to meet the new requirements many times over.

Enter the TDAQ. CTI’s TDAQ (Tire Data Acquisition) system is the leading data acquisition system in the world for Tire Uniformity testing. Designed exclusively for testing tires, the TDAQ electronics simultaneously acquire load cell data, spindle rotation, inflation pressure, and dozens of other machine variables—all with a fine 24-bit resolution and a processing rate of 16,000 times per second.

TDAQ comes in two versions: one 6 x 8 inch circuit board for handling general machine I/O, and one smaller 4 x 6 inch TDAQ-LC box specifically designed for load cell strain-gage amplification and measurement. The TDAQ system incorporates modern electronic design elements—such as adhering to electromagnetic compatibility fundamentals for high noise immunity—and is rated to CE approval standards. Its use of Ethernet-based data transmission allows it to be placed on the machine near the sources of the signals it measures. This feature greatly reduces both signal noise and the amount of field wiring, saving costs in both setup and troubleshooting.

Inflation

Did you know that every 0.002 PSI of air pressure variation during the test directly translates to a 0.1-pound variation in the radial force measurement of a passenger tire? The accuracy and speed of the air system is paramount to achieving good, consistent test results.

In traditional inflation systems, an analog signal is used to control an electronic air regulator, which sets the pressure in the tire to the required testing setpoint. The problem with this approach is that analog signals are highly susceptible to electrical noise. This noise causes the regulator to behave erratically: sometimes floating to a different air pressure, or even correcting itself in the middle of a test measurement.

CTI’s new TAIR (Tire Automatic Inflation Regulator) system solves this problem. The TAIR consists of a stepper motor-powered air regulator commanded by an all-digital interface. When instructed, the TAIR can quickly dial up and hold the correct air pressure just as each new tire enters the machine. This makes it the ideal system for mixed-recipe processing and for testing tires at multiple inflation setpoints.

The TAIR also provides other enhancements. Consider the stage of a tire test just after a bead- seat, when the machine switches from exhausting air to regulating test pressure. Usually, a PLC is used to monitor the air pressure feedback during deflation so it can pick the right time to switch the valves. This same PLC is also controlling every other physical aspect of the machine in real- time, and therefore it cannot react fast enough for the rapidly deflating tire. What often results is a random 'undershoot or overshoot' of air pressure. This causes the air regulator to work harder to bring the tire's air to the desired test pressure, taking several seconds in some cases. Not only is valuable cycle time lost, but inconsistent air regulation can mean the air pressure is still settling during force measurement, causing inaccurate readings.

TAIR easily overcomes this issue with its recipe-specific learning mode. The TAIR builds upon the 1/16,000th-second response time of the TDAQ to close the air exhaust valve at precisely the right moment, such that the air pressure exactly reaches target setpoint every time. Not only does this methodology eliminate time lost waiting for the regulator to correct an 'undershoot or overshoot', its precise timing ensures the ability of the air system to behave almost identically from one tire to the next, increasing repeatability and accuracy.

Loadwheel

On a tire uniformity machine, there are only a couple select parts that take more abuse than the loadwheel. With its ability to press thousands of pounds of force onto a spinning tire, the wheel must be uniformly round to allow the machine to measure force variations in the tenths of pounds. In reality, however, the loadwheel does not stay uniform very long: its gritted surface starts to wear unevenly. A change of only one-thousandth of an inch in the loadwheel’s surface can translate into one pound of force variation when loaded with an average passenger tire.

This much variation can cause the machine to fail Quality Assurance (QA) repeatability tests run by the tire manufacturer. When uniformity machines can no longer be maintained to meet specifications, they are taken out of production until time is available to either rework or replace them altogether. Not only is this repair job expensive for tire manufacturers, but extended machine downtime also reduces total production capability and causes a backlog of tires during peak production hours—a situation no plant wants to be in for very long!

CTI’s solution to this problem is its patented MECC (Machine Effect Characterization and Compensation) process. Using the 24-bit strain-gage inputs provided by the TDAQ-LC, this process can detect miniscule changes in the surface due to wear and subtract out its effects from the tire test results. This process provides a stop-gap measure that allows the uniformity machine to stay in production until the plant can schedule the proper time to do the repairs.

CTI’s MECC process can even be used to enhance a brand new loadwheel. Most loadwheels are built to an out-of-roundness specification that is no greater than .0005 inch around the surface of the wheel. But this .0005 inch still translates to a half-pound non-repeatability for an average tire passing through the machine. Any out-of-roundness—no matter how small—can be characterized by MECC and then a correction process can be used to improve the results of tires tested.

In terms of physical hardware, the MECC characterization process requires only a small amount of hardware to be placed at the loadwheel. MECC uses the hardware to map the loadwheel’s angular position to each point on the surface of the tire.

This same MECC process can also be used to characterize and subtract out machine effects generated by the rims and spindle adapters.

Tune-Up Offer

If your factory runs machines built by The Poling Group, you can expect to soon receive a special offer for a Tire Uniformity tune-up! The tune-up begins with one of our field service engineers using a special uniformity machine survey to determine your machine’s condition, a process that results in an itemized list of potential areas for mechanical and electrical improvement. For many of the installed base of Poling Group machines, a very small investment allows the improvements we described to be installed without the need for a full electrical upgrade.

And if you do not have a Poling Group uniformity machine, your machine tune-up will cost a little more, but when it is complete you will have our flagship TTOC6 controls and all the benefits of the most advanced uniformity controls available.

 
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