Q7 - Kevin Kohls

Q7. How did you "design in" the bottleneck?

That took a lot of time to work out. We had a need to figure out the maximum capacity of the plant, if we had to run full out. We knew this would not be a situation that plant would be in all the time, but it was important if demand got to be so high, we had to consider moving the product to another plant, versus taking on an aggressive improvement plan.

We were also struggling with the basic question of whether we should design in the constraint. But, it seemed more logical to know where it would be, if demand were high, versus just letting fate decide where it would end up. So we started kicking around the issue.

Location was the obvious one. If we had the constraint at the beginning of the system, then we would end up needing less inventory in the facility. The first set of operations in a plant have are typically welding operations (the area is called the Body Shop) that are highly automated with robots and tooling. If we designed it at the beginning, it could be easily moved, just by buying more robots to do more welding in a station. Thus, the bottleneck would not be very “rooted”, and that would defeat the purpose of designing in the bottleneck.

Assembly was the last set of major operations, and there were many good reasons to make that the bottleneck. Assembly has the most operators, and they would be highly utilized as the bottleneck. There were many merge points as well, and choosing the biggest one, where the engine and powertain were merged to the rest of the vehicle looked to be a good point. In Simple Drum-Buffer-Rope, this operation is a perfect point to attach the rope to pull in material.

But line rates could be changed in Assembly, by adding people and changing conveyor rates. The designed in bottleneck could be moved in the matter of a few weeks, if desired. The bottleneck would not be strongly “rooted.”

In the Paint Shop, however, chemistry and physics came more into play in how the area was designed, and what rates were used. In particular, the “dip tanks” became an area of focus. The body, which has been welded and cleaned, is dipped into a tank of paint that provided the undercoating and rust protection. The body has to spend a very specific amount of time in this tank. We cannot speed up the conveyor if we want to increase the rate of production. Expanding the tank is a huge project, and production would have to be shut down for weeks to make it happen. Designing in the bottleneck in here would ensure that it would be rooted. We could improve the system, add robots and people, but the rate of these tanks decided how fast the system would run.

We took advantage of this by adding sufficient buffers around these tanks, and ensuring that the other conveyors in the paint shop ran faster than the dip tanks. We couldn’t do this in all the plants, since a typical Paint Shops last 20 years, but we did get a chance to influence a few of the new plants. The Paint Shop management was doubtful in the beginning, but with strong product launch results, we managed to convince the majority. Now all Body Shops, Paint Shops, and Assembly areas are simulated to ensure excellent launch performance.

Comments

[Robert Roy]

Interesting that you chose the Paint Shop as a good drum. Henry Ford with his famous " You can have any color you want for your Model T as long as it is black" was in fact refering to the drying time of the paint. Th quickest drying paint he found was black. Thanks to Kevin and Clarke for your input.