Previously, I
shared the
six step of value engineering  to
systematically improve the value of a products. Within the functional analysis phase
(step 2) a FAST (Function Analysis Systems Technique) diagram can be used to
deepen the teams understanding of all the functions within the scope of study. The
technique uses “How-Why” logic to help describe the project in terms that allow
for more effective inventive thinking.

The FAST
diagramming is a tool that has been a mainstay with Value Analysis and Value
Engineering (VAVE). The FAST diagram provides a graphical representation of how
functions are linked or work together in a system (product, or process) to
deliver the intended goods or services. By focusing on functions, team and individuals
can focus on what is truly important and not ne constrained by physical
features of products or processes, leading to better definition of the problem
and a clearer path to a solution.

Three key
questions are addressed in a FAST Diagram:

• How do you
  achieve this function?
• Why do you do
  this function?
• When you do
  this function, what other functions must you do?

To Create a FAST
diagram you:

• The first step
  is to brainstorm all the functions the product will serve in the eyes of the
  customer.
• The function
  should be defined as broad and generic as possible, such as produce torque,
  generate light, shape material etc.
• The basic
  function is the overall product function. For example, the basic function of a
  car seat belt is to restrain a person in a car seat.
• The Secondary
  functions:- these are essential to the performance of the basic function and
  they are direct cause to the basic function.
• Secondary
  functions can be categorized into 3 types
• Required
• Aesthetic
• Unwanted by
  product
• Expand the
  functions in the “How” and “Why” directions.
• Build along the
  “How” path by asking ‘how is the function achieved’? Place the answer
  to the right in terms of an active verb and measurable noun.
• Test the logic
  in the direction of the “Why” path (right to left) by asking ‘why is
  this function undertaken?’
• When the logic
  does not work, identify any missing or redundant functions or adjust the order.
• To identify
  functions that happen at the same time, ask “when this function is done,
  what else is done or caused by the function?”
• The higher
  order functions (functions towards the left on the FAST Diagram) describe what
  is being accomplished and lower order functions (functions towards the right on
  the FAST Diagram) describe how they are being accomplished.
• Overall
  function is placed at the top left of the diagram. The sub-functions resulting
  from how questioning are listed to the right of the overall functions.
• This string of
  sub-functions that are critical to achieving the product function is called
  Critical Path.
• Other Functions
  must be listed at the top of the Fast diagram.
• All Time
  Functions are functions that are pervasive to the product. Listed on the right
  of the diagram.
• One Time
  Functions are functions are listed at the centre of the diagram.

Let us take an
example look at how a FAST diagram looks like for a product. Then we can
understand the steps very easily.

The development
of a FAST diagram is a creative thought process which supports communication
between team members.

There is no
‘correct’ FAST diagram but there is a valid method of representing the logic in
a diagram. The validity of a FAST model for a given situation is dependent on
knowledge and scope of the workshop participants. The FAST diagram aids the
team in reaching consensus on their understanding of the project.

The development
of a FAST diagram is a creative thought process which supports communication
between team members.

The development
of a FAST diagram helps teams to:

• Develop a
  shared understanding of the project
• Identify
  missing functions.
• Define,
  simplify and clarify the problem.
• Organize and
  understand the relationships between functions.
• Identify the
  basic function of the project, process or product.
• Improve
  communication and consensus.
• Stimulate
  creativity.

FAST Diagrams
represent a very powerful fool in analyzing complex systems, and boiling down
the descriptions of the functions performed into the essence of the tasks that must
be delivered. The requirement that functions be described in a two-word
verb-noun format is a double-edged sword:

• It promotes
  creative thinking in alternate ways to deliver a function; and
• Limits it by
  constraining the perspective to looking at only positively framed functions.

The How/Why
logical connection between functions serves as an excellent way to verify the
validity of FAST Diagrams, and the focus on functions removes the physicality
from the system (product, process, or service), opening the creative vista and
removing physical and mental constraints in the process. Functional analysis
helps make complex systems more understandable.