What You Need to Know About DOE
Design of Experiments is one the most powerful, yet least
understood and used, of the improvement tools available to
manufacturing organizations. The financial payback period achieved
from using DOE, especially screening experiments, is often measured
in months and weeks, not years. What other investment in time and
resources can generate that level of return over and over again?
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that focuses on Design of Experiments.
DOE's Require Planning
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Design and Communicate the Objective
The objective will generally be one of
three forms: The “Biggest” (to maximize the response), the
“Smallest” (to minimize the response) or the “Closest-to-Target”
(to hit a target)
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Define the Process
Define the boundaries of the process to be
experimented upon. This could be just internal processes or it
could include the full extended process in which the processes
of suppliers and/or customers are studied along with internal
processes.
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Select a Response and Measurement System
Responses are the outputs, or the dependent
variables, of the process. In analyzing a designed experiment,
you can use as many responses as you are willing to measure. A
good measurement system is one that is accurate, repeatable,
reproducible, stable, and linear. Taking good samples is a
critical aspect of the measurement system. The samples from
each experimental run must be representative of the response
during that run.
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Ensure that the Measurement System is
Adequate
Make sure the measurement system has been
calibrated. If the measurement system is not repeatable and
reproducible, the results of the designed experiment will not be
valid. It is prudent to conduct a GR&R before investing in the
time, effort and funds for conducting a designed experiment.
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Select Factors to be Studied
Factors are the independent variables that
will affect the response; select those factors that should have
the greatest impact on the response. Ensure that it is
practical, feasible, and cost effective to select a factor to be
studied and to change its level.
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Select the Experimental Design
The type of design is highly dependent on
the number of factors to be studied. Screening experiments are
usually the best design choice early in an experimental sequence
when many factors are to be explored.
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Set Factor Levels
Be bold and set the levels at the edges of
the operating window for the process when conducting screening
experiments.
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Final Design Considerations
Final considerations include: Selecting
the experimental matrix to use; deciding how to estimate the
experimental error and planning the experiment so that any
external sources of variation are minimized.
DOE Links
Here are some links that will help broaden your knowledge of
DOE.
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