Improving Uniformity: Increasing First Pass Yield Through the Tire Building Machine

By Morgan Allis

Uniformity kick outs in department 614 has been an ongoing issue. The percentage of tires that passed uniformity

testing the first time, also known as first pass yield, was an area the business center wanted to improve upon. Reprocessing

tires, while hard on our employees, also costs the plant money; sometimes ticket is missed due to low first pass yield. .

Before our team began investigating this area of opportunity we verified that the machines that test uniformity,

Kokusai #1 and #2, were taking precise and accurate measurements. Through the implementation of new procedures, including

daily repeatability tests and shiftly rim cleanings, the two Kokusais were verified to be both accurate and precise.

As seen in figure 1, out of all the MTR build machines, TBM #14 has the highest number of kickouts (for a sample size

of approximately 1 week). A significant number of kickouts failed for the test metric most commonly associated with vibration

(radial runout and first harmonic). TBM #14’s low performance was the perfect opportunity to strategically design an

experiment to study the varying factors that affect tire uniformity; this was done through isolation of variables. In order to

achieve accurate results, variables such as builder and green tire #, were controlled for. A multifunctional team was organized

which included engineers, PQAMS, BCMs, TTLs, tire builders, FARO mechanics, and PM mechanics.

Figure 1. Pre-Alignment Kickout Results [10/28-11-04]

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TBM Kickouts Before Improvements

The first variable to be studied was machine alignment. With invaluable data from the FARO alignment team it was

obvious that there was room for improvement. In conjunction with each other, the PM mechanics and FARO mechanics

efficiently aligned the build machine. The alignment included shaft-to-transfer-ring alignment, transfer ring to belt drum

alignment, and transfer ring to former alignment.

As seen in figures 2 and 3, the impact on uniformity from the TBM alignment was significant. First pass yield increased

from 72% to 98% (figure 2) and the overall number of kickouts significantly decreased from a weekly average of approximately

550 to 23 (figure 3). That is, our employees went from needing to handle tires 28% of the time to 2% of the time. This equated

to a significant amount of time where operators and PQAMs could work on other tasks.

Figure 2. Post-Alignment First Pass Yield Uniformity Results for TBM 14

Figure 3. TBM 14 kickouts [10/11-11/15]

Moving forward, while closely working with the FARO team, we plan to apply our findings to more build machines,

while at the same time also isolating and studying other variables such as centering capability, splice capability, green tire #,

and any other relevant variables. The study has demonstrated that build machine alignment is a critical component of tire

uniformity. Furthermore, the alignment results demonstrate the value that the FARO alignment team brings to the quality of

our product. Eventually we will use our findings to drive the quality of our product throughout all three business centers.

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Uniformity First Pass Yield

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Week AfterAlignment

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Alignment Completed