Page 287 - How To Implement Lean Manufacturing

264 Cha pte r S i x tee n

Changeover * Load Machine Unload Total
Large 3 min 0.5 min 4.5 min 0.5 min 9.5 min
Small 3 min 0.5 min 3.5 min 0.5 min 8.5 min

∗ Actual changeover (CO) time was 45 minutes, averaging about 15 units per changeover. A unique
holding jig was required for eight of the ten models. An average of eight COs occurred each day.

TABLE 16-11 CNC Lathe Cycle-Time Elements

We Reduce the Lathe Cycle Time
A breakdown of the lathe cycle time is shown in Table 16-11.

Kaizen Opportunities in Synchronization
The following were kaizen opportunities we could exploit from improvement ideas in
both external and internal synchronization.
• It was clear from the balancing chart that the CNC lathe cycle time was the
bottleneck, and both models ran at a cycle time exceeding takt. Thus, we needed
to reduce the average cycle time. After some analysis, we decided to prepare a
universal holding jig for small motors and one for large motors. This would
reduce the number of changeovers to as few as five per day. Also, using Single
Minute Exchange of Dies (SMED), quick changeover technology, we were able
to reduce the changeover time to 11 minutes.
• Shut down one winder—this was not required—and go to three operators for
the wire coiling cell.
• Model-mix level the production work. The complexity in leveling was in the coil
insertion cells. The work to insert coils on a large stator averaged 105 minutes.
The work for an average small stator averaged 80 minutes. To level the model
mix, we would need two cells of four operators each on the large stators, which
would average a motor every 26 minutes/cell (105 min/4 stations per cell). We
would also have two cells of three operators each on the small stators and
average a motor every 27 minutes/cell (80 min/3 stations per cell). Overall, we
would have a cycle time across all four cells of 6.6 minutes. This was below takt,
yet close enough to avoid overproduction.
• Other opportunities might be possible in staffing the insertion cells and the
lacing island.
• Eliminate the polishing step since it was no longer needed.

Creating Flow
It is worth noting that during the making of the present state VSM, all production
stopped at coil insertion, and the flow went to zero. Mother nature will always find the
hidden flaw. A quick investigation showed there was no wire made with the proper
coiling. Yet all 40 transport trees were 100 full. On the floor, we had over four days of
coiled wire but none of it matched the demand at the cells. This, of course, was the
direct result of sending planning information to multiple points on the value stream.
In addition to the planning issues, creating flow was achieved by balancing the flow,