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Featured Story
Whirlpool Corporation's Marion, OH Division, which specializes in dryer units, recently modeled its conveyor system for a new dryer drum, the main part of the dryer in which consumers put clothing.
Within the division, we had a difference of opinion as to what the best solution would be to this problem. In essence, we had three options. One part of the operations group felt that we needed an additional storage conveyor line for the new model. The other camp proposed making changes to the existing drum service line, which feeds directly into the assembly area. A third, less feasible option consisted of changing the drum at the line and adding more room to the assembly area.
We created a Microsoft Excel spreadsheet to help us analyze the three options, but that didn't really tell the story. It only gave us minute-by-minute data and didn't show what occurs later on in the system in terms of output. At first glance, it seemed that we would most likely have to come up with a system that combined both lines. But instead of relying on our own gut feeling, we employed the services of ProModel.
Our initial single drum setup consisted of flatware being transported underneath the drum on another hook, except for every fourth pair of hooks, which was capable of handling 2 drums. The flatware consists of the dryer bulkhead, the back of the dryer, the stationary drum front (front of the dryer) and an inner door. Ultimately, the model showed us the best way to change the hook configuration of the materials they transported. Instead of transporting the flatware beneath the single drum, we came up with a configuration that consisted of the old drum model on the bottom and the new drum model on the top, with the flatware to the outside. Using simulation, we also came up with optimal parameters for hook spacing (distance between pairs of hooks on the conveyor), conveyor speed, and shift scheduling. Using the optimal parameters determined from the simulation experiments, we were able to achieve the same speed with the two-drum system that we were running with the one-drum system. With regard to shift scheduling, we were able to coordinate shift/start times between the drum assemblers and the dryer assemblers. The people who were assembling the drums were coming in earlier, and we weren't getting much benefit from that. The workers in the drum manufacturing area in particular didn't like following the same shift pattern as the other area and wanted to start earlier. But the simulation showed that things ran smoother when they both started at the same time.
We learned quickly that simulation requires discipline - you have to do what your simulation tells you to do. A couple of months into the project, one of our supervisors reported that the system wasn't working very well. He argued that the simulation wasn't living up to expectations. In reality, he wasn't following the recommendations that resulted from the simulation project. We haven't had any problem since everyone in that area actually began implementing the recommendations and doing what the simulation said to do.
By making only minimal changes to the existing system, we obtained estimated savings of approximately $108,000 (the cost of putting in additional storage using the separate conveyor line). Simulation showed that, if we made some changes, we could avoid that cost. All told, we ended up modeling the existing line only. We could have done simulation on the more expensive alternative, but after discovering that our current system would indeed meet the demand, the need was no longer there.
Whirlpool has yet to implement all of the findings that surfaced from the simulation project. At the present time, however, we're as high as we're going to be for a long time in terms of production levels. If capacity is an issue down the road, we'll implement the other recommendations.
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The system is
further complicated in the sense that when something is put on a hook at
the drum manufacturing area, there's a significant time lag until it gets
taken off at the final assembly area. In fact, a particular drum may make
several trips around the conveyor system before finally being taken off at
the final assembly area. The main goal in the drum manufacturing area is
to assure that the final assembly area doesn't shut down. This is
accomplished by always having enough drums on the service line. Because of
these different complexities within the system, the use of simulation was
necessary. We proceeded to gather the necessary data and build the model,
including parameters such as hook speed, hook configuration, conveyor
speed, downtime, and shift schedules.