| An
investment foundry manufactures small parts for aircraft and
stationary turbine engines. The technology is difficult, and
unpredictable. Much of the equipment is large scale. There are about
4000 active part numbers with wide variations in routings and work
content.
Several years before, some of their
engineers had attended a large-scale Kaizen Blitz. These engineers
had accepted the usual dictums about "One Piece Flow"
and "Sequential Arrangements". But, the complex
product and process mix had baffled all attempts to put these
dictums into practice. As a result, nothing had been done towards
implementing workcells.
A Strategos consultant implemented
the first workcell within a few days. It functioned well with
impressive results.
Subsequently, the firm's engineers
attempted to implement a workcell in different area with very poor
results. What had gone wrong with this second cell?
The primary issue was "One Piece
Flow". The engineers had accepted this dictum quite literally.
But the product and process did not lend itself to One Piece flow.
Operation times were very short, about 15-20 seconds. The parts were
very small (about 1-1/2"). One process step, shot-blast,
required a large number of parts in order to function properly.
Compounding this was the excessive distance between machines. |
Operators
spent more time walking parts than they did processing the parts.
The shot blast machine was eating itself alive because the blast
impinged on the machine parts rather than workpieces.
When inquiries were made about why
only a single piece was moved, the answer was, essentially,
"Because that fellow from Nagoya told us we had to do it that
way."
One Piece
Flow is an ideal that engineers should strive for.
But, it simply does not work when the transfer time begins to
approach the work time. Nor does it work with certain processes such
as shot blasting.
The people involved had great
difficulty in reconciling their deeply held faith in "One Piece
Flow" with the realities of the situation. The problem was
resolved semantically.
The word "piece" was simply
redefined as 20 castings . Small carriers were built to carry the 20
castings or in Newspeak, the single piece. In addition, queues were
setup to allow accumulation of a reasonable quantity for shot
blasting. In this way, each transfer time was amortized over 20
parts instead of just one and the shot wheel had something
worthwhile to blast on. The cell began to function effectively.
This project was the genesis of Mr.
Lee's subsequent works that bring order, structure, and rationality
to the cell design process. |
