Lean Implementation Strategies and Tactics 405
Chapter 19. Lean Implementation Strategies and Tactics 405
distributions, box plots, and a four-way probability plot. Also, more traditional lean tools were used, such as listing the process steps and determining which could be done externally while the machine was running and which had to be done internally while the machine was down. These activities were prioritized, from those taking the most time to those taking the least. A fishbone diagram of the materials, man, methods, machine, measurement, and environment causal factors effecting inefficient changeovers was developed. The top two causal factors were identified as waiting for a changeover cart and the process of heating the die, which accounted for 38 percent of the changeover time, or 1.3 hours per changeover. They also discovered 12 of 22 other steps that could be done while the machine was running (external).
The Black Belt in training generated a brainstorm of ideas for improvement with some input from the floor. This was narrowed down to action items to be implemented:
◆ Schedule mold changes to coincide with lunch breaks so the dies could be heated during lunch (they could not justify the cost of
equipment to preheat the dies). ◆ Add one additional cart, which would be enough to optimize the
carts needed. ◆ Assign a dedicated changeover team instead of asking operators to
do it, so they could prepare a lot of the external changeover items while the machines were running.
The results exceeded the goal. Detailed data were collected, put on run charts and statistically analyzed. It showed significant improve- ments. The result was a 98 percent improvement resulting in 2,828 parts per million defects (defining a defect as a changeover taking more than 2.5 hours). The average changeover took 1.2 hours, well below the 2.5 hour target. Analysis of the savings focused on the reduced amount of labor for changeovers, which amounted to almost $300,000 per year. Actually, the number of changeovers done in a week was over the budgeted number, and they had a parallel program to stabilize the schedule and reduce the number of changeovers. So there were arguments about whether her project should get credit for the labor savings based on the current number of changeovers or on the anticipated reduced number of changeovers.
So this was a big success, right? Or was it? Let’s consider what’s wrong with this picture:
1. The total process took several months. Much of that time was spent on sophisticated statistical analysis and preparation of
T HE T OYOTA W AY F IELDBOOK
presentation materials. If an experienced lean specialist did this, it could have been done within a one-week kaizen workshop.
2. The young engineer did most of the work while working mostly alone. There was little involvement or buy in of the workforce in the area.
3. The young engineer ruled out some of the most important ideas. For example, she ruled out preheating the molds, which would have had a major impact. A more experienced manufacturing change agent would have fought for this.
4. The objective of 2.5 hours is not a challenging goal, and even
1.2 hours is not a stretch objective for an injection-molding changeover. A more reasonable goal would have been 15 to 20 minutes, and a stretch objective would be five minutes, which is done routinely in lean plants. A 15-minute changeover could have allowed for more changeovers, reducing batch size, and still reduced the amount of labor significantly.
5. The overall value stream became less lean. There was no value stream map done. After the fact, a map showed that there had been five days of injected molded parts after molding, before the changeover reduction activities. By reducing the time of changeovers, doing changeovers only around lunch, and then reducing the number of changeovers, days of molded parts inventory actually increased, increasing flow days. Value stream mapping would have suggested reducing changeover in order to increase the frequency of changeovers to drive down inventory.