JIT and the job shop

Modern Machine Shop, April, 1992 by Tom Beard

The obvious advantage of such a system is less work-in-process, but the inventory reduction is only a small portion of the benefits. What they essentially are doing, says Mr. Thul, is "breaking the big shop into little shops that are highly focused. Now you can prepare better. You can do on-thefloor job planning. And the whole group of people is focused on the total job. It is much easier to improve throughput when everyone is focused on the entire system."

This close grouping of processes has produced impressive results. Mr. Thul figures that the "yarn" of part travel--that is, the physical distance a workpiece travels over its entire manufacturing process--was reduced by 90 percent. Moreover, jobs that once took an average of eight weeks to get through the shop now pass through in two and a half days.

Such results, though, are not just due to what's happening on Arizona's own shop floor. They've also established a kanban with their material suppliers, and typically will receive sheet stock no more than 24 hours before it is used. They still find it necessary to keep a little buffer stock on hand, to make up for scrapped parts, for example. But now they may have 20 sheets of stock where they once had a warehouse. Overall, the amount of raw material they used to average has been cut by 75 percent.

Problem Solving

One of the often-cited advantages of JIT is that it brings clarity to shop floor problems, and forces a quick response. By eliminating or drastically reducing the buffer of work-inprocess inventory, the output of each station is heavily impacted by the weakest link in the processing chain. Thus, it becomes a matter of urgency when one operation has quality or output problems, because it will directly diminish the productivity of the entire system.

This is both how and why Arizona Precision takes an aggressive approach to problem solving. It begins with training. Besides the cross-job training that allows each cell member to understand all phases of the manufacturing process, workers mu st learn techniques to ferret out production problems, and to develop solutions in collaboration with their coworkers. Early on, production management set up pilot project teams to tackle problems that would clearly be impediments to achieving the company's JIT goals. In a structured process, the teams would work together to develop an action plan that would first be presented to management, and then to their coworkers.

A key to this methodology is to rely on the direct input and analysis of the shop floor workers themselves, and not simply in order to make them feel more involved. Mr. Thul cautions that a manager should not attempt to shortcut the process, based on his own notion of how an issue might be resolved. He says, "You have to be willing to let the process take its course, even if you think you have the answer, because the manager's answer may not always solve the real problem."

One of the largest successes so far has been in the reduction of setup. The need was clear. To achieve the shop's JIT objectives, lot sizes would have to shrink, and consequently, the frequency of setups would have to be doubled.