Page 140 - Six Sigma Demystified

Chapter 6 a n a ly z e S tag e 121

to eat only a few freshly baked cookies tonight, then a few freshly baked cook-
ies tomorrow, and so on. What we really would like is a small oven that could
quickly cook only the number of cookies we want to eat now! Since we need
the same oven for Thanksgiving and for tonight’s cookies, we are forced to bake
the full batch and eat them before the inventory gets stale (or throw out the
unused inventory). Fortunately, the process can be redesigned with smaller
batch sizes by using a smaller toaster oven for tonight’s cookies.
When setup time dominates a process, it seems natural to process as many
items as economically feasible so as to spread the setup costs across the batch.
Until 1990 or so, the printing presses used for producing textbooks required
elaborate setup procedures, taking several hours per book title. For this reason,
publishers and resellers were economically forced to order large quantities to
keep the unit price affordable. Often this resulted in excessive inventories,
which served as a disincentive to revise the book with new material. When the
setup times were reduced, smaller batch sizes become efficient, as is now com-
monly practiced in the book printing industry.
Setup time can be defined as the time to change from the last item of the
previous order to the first good item of the next order (George, 2002). Setup
includes four main activities: preparation, replacement, location, and
adjustment.
Preparation refers to the tasks associated with getting or storing the material
or information needed for the process— obtaining the raw material from the
warehouse, pulling up the process instructions from the computer, moving
completed items to the next process step, starting up the software needed to
process the order, and so on.
Some suitable actions to reduce the time associated with preparation include

• Convert from departments to work cells to minimize the time required to
move the finished product to the next process step.
• Store tools and materials locally, such as advocated by the 5S principles.
• Convert to “always ready to go.” Make the software or instructions in-
stantly accessible.

Replacement refers to the tasks associated with adding or removing items or
tools, for example, moving test fixtures, loading new material into a hopper, or
loading paper in a copy machine. Actions to reduce replacement times include

• Simplify setups. Reduce the number of steps required, such as through a
redesign of fixtures.