Page 81 - How To Implement Lean Manufacturing

62 Cha pte r F o u r

process parameter. It is crucial to understand the variation in the measurement
system since it detracts from the capability performance of the process. Frequently,
process performance can be improved simply by working on the variation in the
measurement system.
Cp and Cpk Cp and Cpk are the industrially accepted measures of process perfor-
mance. They are both called process capability indices. Several good books describe
how to calculate Cp and Cpk, but one major point of understanding must be accepted—
specifically, Cp and Cpk have no meaning if the process does not exhibit process
stability—that is, process predictability. Process stability is best evaluated using a con-
trol chart and is absolutely necessary for Lean initiatives to be implemented. Nothing is
more basic to successful Lean implementation than process stability.
Availability Availability is the concept that the production process shall be capable to
produce product, when it is scheduled to do so. High process availability is a necessary
characteristic of a process ready to be Leaned out. Low process availability is almost
always a sign of an unstable process. Usually, low availability is associated with machin-
ery downtime or the inability to deliver on-spec raw materials to the production line.

Cycle-Time Reductions Cycle-time reductions are very important to Lean implementa-
tions. It is best to work hard on cycle-time reductions prior to implementation of a Lean
initiative. This helps stabilize the process and then the quantity control issues are more
easily managed. However, often during a Lean implementation, cycle-time reductions
will be found and they usually translate directly into higher production rates. These
cycle-time reductions are truly the “low hanging fruit” of Lean implementations. Any
time a cycle-time reduction can be achieved, the resultant extra production is the lowest
cost product you can make. Basically, you are transforming the cost of raw materials
into the value of the finished product.

Standard Work Standard work, as defined by Ohno, has three elements:
• The cycle time
• The work sequence
• The standard inventory
However, it is a much misunderstood concept. In his book, Ohno says, “…I want to
discuss the standard work sheet as a means of visual control, which is how the Toyota
production system is managed.”
Notice he uses two interesting terms. First, he uses the term “visual control,” and
second he says it is how the TPS is “managed.” He does not say, “this is how the TPS
is operated.” He is very specific, so do not be confused. This explains why, when you
enter a Toyota facility and see the standard work sheet at a work cell, it is not facing
the operator. Rather, it is facing the aisle so it is available to the supervisor, the engi-
neer, and the manager. Standard work is not used by the line operator but by the team
leader, engineer, or manager so they can audit the work, understand the status of the
process, and provide assistance if the process is not performing as designed. The stan-
dard work chart is part of the concept of transparency and is there for visual control
by the management team. It is a myth that the Standard Work Chart is made for the
operator.