How Saturn improves quality by reducing variation

In Spring Hill, TN, they say, "There may be many ways to solve problems, but at Saturn, there is only one precise way to build a car." Research in the field of total quality management consistently indicates that variation in how job processes are performed is one of the biggest barriers to achieving consistent quality. The Saturn plant in Spring Hill has always used the team approach to find the best means of reducing process variation and has achieved some spectacular results. Recently, however, something new was added.

Saturn's Vehicle Interior Systems (VIS) Div. was chosen to pilot a program to achieve QS 9000 certification at the plant. Certification will lead to a significant expansion in the scope of business at VIS. For example, VIS soon will also mold exterior parts-fascias-on two new 5000-ton Next Wave HPM two-platen molding machines, the largest of their kind ever built. And VIS intends to pursue work outside of Saturn with other carmakers. So the need to reduce process variation has never been more important.

IMM spoke with two VIS team members about Saturn's quality programs. They are Kay Case, a 24-year automotive molding vet who is a tooling and process engineer at VIS, and Walter Bell, an experienced VIS quality technician. They agree that, first and foremost, Saturn's team members pay strict attention to "operator descriptions" for each job. These written worksheets, which may include visual aids, eliminate having each of the 8000 Saturn team members building cars by performing all the tasks involved in their own individual way. One standardized approach is followed for each job, ensuring consistency from operator to operator, crew to crew, and car to car.

"These are documents written in the initial phase of the process, but they are living documents," Case explains. "Our engineers are responsible for incorporating any engineering change through a PPAP [production part approval process] into the operator description, or anything that's done that may affect the process in any way."

The Total Quality Action Team (TQAT) approach to problem solving, a Saturn original, also has been used to reduce variation at the Spring Hill plant. Bell describes TQAT as a methodical, six-step process that can be initiated by any team member. Once a problem resulting from a process variation is spotted, cross-functional teams adhere to the following procedures, while keeping their eyes on flow charts of the process in the problem area every step of the way:

1. The problem is initially described.

2. An interim action is developed to keep the process working.

3. A brainstorming session is held to analyze the problem.

4. A final solution is then developed.

5. The solution is next validated through trial production.

6. If successful, the solution is made permanent.

"We're just now winding up one TQAT project," says Bell. "It was on a purchased part, a dome light for our headliners. We were losing bulbs. We worked in a partnership with our supplier on this one and came up with a permanent fix, one with good bulb retention, in less than one month after the TQAT started."

Perhaps more importantly, team-based quality approaches also help VIS to eliminate process variations before they occur. Both Case and Bell have high regard for the computerized Allen-Bradley and GE Fanuc process control systems on their existing Ube molding machines, and for the machines themselves, in reducing variations in part weight, a key process control parameter at Saturn. Furthermore, every molded part is 100 percent visually inspected, and boundary samples are checked on coordinate measuring machines to ensure that dimensional tolerances are being held.

Maintenance teams also play a very important role. "They own our PM [preventive maintenance] programs," Case says. "We make sure to allow the production time to do regular PM on the machines, and we take the same approach to tooling." All VIS mold cycles are monitored and the individual cycle counts are networked into Saturn's plantwide CIM system. Once a mold cycles 45,000 times, the system alerts the maintenance team that it's time for PM.

"It's sometimes easy to forget that uptime needs some downtime to solve problems," Case notes. "Saturn builds in allowances for maintenance downtime." And Bell adds, allowances are made for the best use of team members' time, as well as mold and machine time. "We assign three machine operators, one from each crew shift. They do 90 percent of the tweaking to get things right." Such concerns about time are understandable. Saturn uses no backup tooling and it inventories only 11/2 days worth of molded parts.

QS 9000 procedures, which should reduce process variations even further, should not prove to be very difficult to adopt at Saturn VIS, since it has so many QS-friendly approaches already in place. For example, certification will involve representatives of various departments to work together in teams. Saturn has been team-structured since Day One. And it's also always been customer focused on the ultimate customer, the car buyer. Still, the QS 9000 seal of approval is essential to its plans for the future, especially since VIS intends to start bidding on outside work. Yet Case says QS disciplines are equally important to keep VIS focused on satisfying its in-house customers.

"I am a supplier of interior parts to Saturn's General Assembly department. That is my immediate customer. All suppliers have to be properly certified to be recognized. We've taken it down to that level here within Saturn. And we intend to be recognized as a world-class vendor to other customers outside the company."

Meanwhile, its programs to improve quality by reducing variation already have brought new business into VIS. In June, ground was broken for an expansion that will add the 20,000 sq ft of floorspace necessary to house its two new 5000-ton HPMs to mold fascias. The fascia tools will be complete by the end of the year, and parts production is expected to begin in the first quarter of 1998. Other parts also may be inherited from Saturn's growing Body Systems Div. in time, and VIS may insource production of some parts Saturn presently outsources. Saturn as a whole is also benefiting. Saturn has consistently earned the highest scores within GM in its corporate quality audits. And when it comes to its ultimate customers, Saturn's 1997 sedan ranked first for initial quality in the annual J.D. Powers and Assoc. survey-ahead of Toyota, Nissan, and Honda.