Page 254 - Lean six sigma demystified

232 Lean Six Sigma DemystifieD

What Is Variation?

Every process varies from its target value: It takes a little more or less time; it
makes the product a little bit bigger or smaller, longer or shorter, wider or thin-
ner, taller or shorter, heavier or lighter, or fuller or emptier than its ideal target
size, shape, and so on. The variation may be large or almost undetectable, but
it’s still there. The goal of Six Sigma is to reduce the amount of variation so that
your product always fits well inside your customer’s specifications for it and
hopefully centers on a target value for that product.
Manufacturers get into trouble when they produce products that don’t fit
the customer’s requirements. Services get into trouble when they can’t meet
the customer’s requirements for timeliness.
Imagine for a moment that you’re producing piston heads for an engine. The
piston heads have to be the right size to fit inside the engine block. If they’re
too big, they won’t fit. If they’re too small, they’ll leak oil and make noise. And
they have to be round so you might want to also measure the roundness of your
piston heads. Because you produce these piston heads using machinery, you’ll
have to factor in the variables: density of the metal, pressure, temperature, and
so on. With so many factors, it might take some effort to produce a consistent
product that fits the customer’s needs.
Now imagine you’re producing plastic bottles for a bottler. The product has
to be a certain shape and height. It has to hold a certain volume of liquid. It has
to seal properly. Using injection-molding machinery, your product will be
affected by the temperature of the mold and the plastic. It will be affected by
not only the pressure of the injection but also by the atmospheric pressure. The
formula of the plastic may affect its ability to accept printing and labeling. The

thickness of the plastic will affect its durability. It will take some efforts to
ensure that you can produce a consistent product that’s easy to bottle but
doesn’t waste material.
Now imagine that you are a bank. Customers arrive randomly. You have a
certain number of tellers scheduled for various times of the day. You know
customers don’t like to wait for a teller, but how do you adjust your staffing to
minimize your cost and minimize your customer’s wait time?
Get the idea? Every process has a variety of variables that affect your ability
to produce a consistent product or deliver a consistent service. There’s going to
be variation. Your job, using Six Sigma, is to find ways to reduce the amount of
variation to a level that meets or exceeds your customer’s expectations. You can
affect variation by changing what used to be called the five M’s: man, methods,