Functional Descriptions
Documenting Product Specifications
© M. Reber
6/27/2016
Definition of a Functional Description





An overall description of the function and
appearance of the entire mechanism
A description of the function and appearance of
each major part of the mechanism
An explanation of how the mechanism operates
and how each part contributes to the functioning of
the whole
Functional Descriptions focus on physical,
quantifiable details
They are often also called a mechanism description
or a product specification
2
What Functional Descriptions are NOT


Not typical user instructions or documentation
Not comprised of steps or “how to“ instructions
3
Uses of Functional Descriptions



To instruct the assembler/repairperson
To market a product to prospective buyers
To explain a product to an owner
4
Functional Descriptions are Organized:

By location (spatially)
 If you are describing a car for new owners, you might
organize according to location so that your reader will
learn about the comforts and conveniences available
to them when sitting in the passenger compartment

According to function
 If you are describing a car for mechanics, you might
organize according to function so the reader can
effectively diagnose and correct problems
5
Parts of a Functional Description


Title
Introduction








Names the object
Explains origin of the name
Explains its function or behavior
Describes its overall appearance
Lists its individual parts
Sections for the various parts
Drawings and other graphics
Conclusion
 Explains how it works (NOT how to operate it!)
6
Extended Descriptions May Also Include:




A scope statement: Indicates what you will and will not
specify and who will have which roles and
responsibilities
A definitions section: Establishes the meaning of any
specialized terms (both the scope statement and
definitions section can be incorporated into the
Introduction if they are short enough
A materials section: Specified required materials to be
used
An operating characteristics section: Lists operational
requirements (such as how much load the product can
bear) for design and construction purposes
7
To Write a Functional Description:
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
Choose a product requiring description
Define the purpose, audience, and situation
Research the mechanism as appropriate
Identify the parts and subparts
Plan the overall description
Sketch the headings you’ll use
Select the sources of description
Plan an introduction
Consider the format
Review and revise your draft
8
Document All “Sources of Description”






Purpose: How is the item used? What are the
applications?
Size: How big or small is it? Can you compare
its size to something familiar?
Shape: How is it shaped? Can you compare its
shape to something familiar?
Color: What are its colors?
Texture, finish: How does it feel to the touch?
How does it look (shiny, dark, etc.)?
Dimensions: What are its length, height, width,
depth?
9
“Sources of Description” (cont.)





Weight: How much does it weigh?
Materials of construction: What materials were
used to create it—wood, steel, cardboard?
Ingredients: If it is something that is mixed,
what are the ingredients?
Methods of attachment: How are the different
parts attached—glued, welded, bolted, screwed,
nailed?
Location, orientation of parts: What’s the
orientation of the parts to each other—above,
below, to the left or right, within?
10
“Sources of Description” (cont.)






Age: How old is it?
Temperature: Is temperature an important
descriptive detail?
Moisture content: What’s the percentage of
water content?
Amounts: How many are there?
Capacity: How much can it hold?
Volume: What are the various measurements of
volume related to it?
11
“Sources of Description” (cont.)


Smell, odor: What does it smell like?
Pattern, design: Does it have a certain pattern
or design associated with it?
12
Tips for Writing Functional Descriptions



Be accurate!! (a small discrepancy in
measurement might mean an object won’t fit
where your reader needs it)
Be specific and concrete (give parts a name,
etc.)
Use simple language and analogies to help
readers visualize
13
Questions to Ask Myself
1. What is my purpose?
2. Who is my primary reader and what are his/her
needs?
3. How can I learn about the object and its
function? (experimentation, literature)
4. What major headings do you plan to use?
5. What should my overview contain?

A definition, a purpose statement, general
appearance, illustration, a list of components?
14
Questions to Ask Myself (cont.)
6. How is the breakdown and description of parts
organized? Is the organization logical?
7. Have I thoroughly described each part and
broken it into components if necessary?
8. What pictures and graphics effectively explain
the object? (Cite your sources.)
9. Do I need a conclusion?
15
Your Assignment

Choose an object or simple machine you are already
familiar with and have at your disposal. For example:






Blender
Air popcorn popper
Blow dryer
Electric razor
Write a description of three to five pages (model specific
if possible)
At a minimum, you should have three parts:
 An overview or introduction section
 A breakdown into parts with descriptions
 Conclusion (explains how the object works)
16
Tips for Completing Your Assignment





Understand the purpose and the audience
Be model-specific
Do not do any outside research!!
(graphics excepted)
Learn about the object through experimentation
Be sure to provide citations for any graphics you
did not create
17