Page 358 - The Handbook for Quality Management a Complete Guide to Operational Excellence

344 C o n t i n u o u s I m p r o v e m e n t I m p r o v e / D e s i g n S t a g e 345

3. A proper SIPOC analysis (as discussed in the Define stage, Chap. 13)
ensures a thorough understanding of the process and subprocesses.
4. Step 4 is perhaps the true beginning of the FMEA process within
Six Sigma DMAIC projects, since the preceding three steps have
already been accomplished and serve as “inputs” at the Improve
stage. In this step, we define the function of the process. The function
provides the purpose of the step. Each step should have one or
more functions, given that the step is necessary to satisfy an
internal or external requirement. To identify the functions of the
process step, it might be useful to consider the ramifications of
removing the step. For example, in a sales process, the process
step for “Enter the product ID number for each purchased item”
provides the function to “Identify the item numbers that belong to
the products being purchased so that they are all included in the
delivery.”
5. For each function, identify failure mode and its effect: What could
go wrong? What could the customer dislike? For example, for the
function “Identify the item numbers that belong to the products
being purchased so that they are all included in the delivery,” the
failure modes might be “Product ID mistyped” and “Item numbers
not correctly defined for product bundles.” The second failure
mode refers to products that are sold as sets. A single item number
is used for the set so that the proper charge is applied for the set
(discounted from the per item prices), but subsequent process
steps (and subsequent processes) need the correct item numbers
for each piece (such as to check inventory levels or fill the order
from inventory).
6. Define the severity for each of the Failure Modes. Table 16.1
provides a good means of identifying the severity for a given
failure effect. In the example given, the failure mode of mistyping
the product ID, with the effect of shipping the wrong product, is
given a severity of 6. From Table 16.1, severity 6 is described as
“Customer will complain. Repair or return likely. Increased
internal costs.” Granted, defining a severity level is subjective. A
severity of 5 or 7 might seem reasonable in this example. There is
no one “right” answer; however, consistency between analyses is
important for meaningful prioritizations.
7. Define the likelihood (or probability) of occurrence. Table 16.1
provides useful descriptions of occurrence levels from 1 to 10.
Table 16.2 provides a somewhat better definition, as developed by
the Automotive Industry Action Group (AIAG) based on process
capability and defect rates. In the example, the failure mode of
mistyping the product ID, with the effect of shipping the wrong
product, is given an occurrence level of 5.

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