Page 253 - How To Implement Lean Manufacturing

The Story of the Bravo Line 231

The quantity control tools would have been much less effective if the quality control
issues had not been addressed. Taken all together, these tools then improved the perfor-
mance and the following occurred:

• Quality was improved.
• Lead times were reduced.
• The cost to produce was reduced.

These three are the key objectives of Lean (again, refer to Chap. 20).

Application of “The Seven Techniques to Improve Flow”
We can employ seven basic techniques to reduce lead time and improve flow (see
Chap. 5). The following describes how they were applied to the Bravo Line.

1. Reduce processing time Here the major gain was achieved through the
reduction of defects and especially the reduction of rework, which had become
a part of the normal process. All the rework was simply non-value-added time.
Regarding the necessary work, here we did nothing to intentionally reduce the
processing time, although the time decreased as the operators became more
engaged in the process.
2. Reduce piece wait time This is the time a single piece is waiting to be
processed. Here the wait time is reduced by balancing, so the flow is synchronized.
In the original case, the cycle time was controlled by station one at 35 seconds,
so it took 35 seconds per station, times nine stations in Cell 1, to go through the
line, or 315 seconds, but only 207 seconds of work were performed. There were
108 seconds of wait time per piece caused by poor synchronization at Cell 1
alone. Again, in this case, the wait time was reduced, but it did not have a large
effect on lead time; however, it certainly made the process flow better. Following
the rebalancing of the work the gains achieved by reducing piece wait time
were found in manpower reductions.
3. Reduce lot wait time This is the time that a piece, within a lot, is waiting to be
processed. In this case, it is substantial and adds to the overall lead time, but
more importantly it adds to the first-piece lead time. This time is often overlooked
but is incredibly important. There will always be quality and production issues
and these issues must be uncovered quickly so they can be solved. If the lot wait
time is like the original case of the Bravo Line, it takes 3.9 hours for the first
pieces to get to final inspection. If a problem is found at final inspection, we now
have over 400 pieces to inspect and rework—for each problem we find. If the
lead time is shorter, the problems surface more quickly and we can react more
quickly. In our first run, we stopped five times in the first batch to correct
problems. This impact alone could have accounted for the huge excess in labor
expenses to run this line in the base case. To reduce lot wait times, shrink lot
sizes as we did here. The goal of minimum lot sizes is one-piece flow.
4. Reduce process delays This is the time an entire lot is waiting to be processed.
Often it is called queue time. Here we were able to reduce it from an average of
49 hours to 6 hours. This is caused by lack of synchronization and also by
transportation delays. Close coupling processes, or making them in the same
cell, mitigates this problem. Kanban can help this, but kanban is only a way to