6.2 Functional Analysis: Tools For Establishing Functions

Question 1

What is design intended to do?

Answer 1

Design is intended to transform inputs into outputs.

Question 2

How do we apply design to transform inputs to outputs?

Answer 2

In order to transform inputs into outputs through design in the following way:

• Define the boundary between our device and its surroundings
• Examine the inputs to and outputs from the device that cross that boundary

Question 3

What are some tools that can be used to establish functions in terms of inputs and outputs?

Answer 3

Some tools that can be used to establish functions in terms of inputs and outputs include the following

• “Black box” - no idea what’s inside
• “Transparent” box - inside known
• enumeration
• dissection or reverse engineering
• function-means trees.

Question 4

What tool is used for elucidating connections between inputs and outputs?

Answer 4

The black box is used for elucidating connections between inputs and outputs.

Question 5

Explain the black box method.

Answer 5

The black box:

• a graphic of the system or object being designed,
  
  • with inputs shown entering the box on its left-hand side
  • with outputs leaving on the right.
• All of the known inputs and outputs should be specified, even undesirable byproducts that result from unwanted secondary functions.

Question 6

Should undesirable byproducts that result from unwanted secondary functions be specified in the black box depiction?

Answer 6

Yes. For the black box, all of the known inputs and outputs should be specified, even undesirable byproducts that result from unwanted secondary functions.

Question 7

How might we organize inputs and outputs for a power drill into a black box diagram?

Answer 7

Question 8

Make a transparent (glass) box for the following black box example.

Answer 8

Question 9

What questions are you trying to answer via dissection or reverse engineering?

Answer 9

Dissection or reverse engineering serves to answer the following questions:

• What does this do?
• How does it do that?
• Why would you want to do that?

Question 10

What is the purpose of dissection/reverse engineering?

Answer 10

For a device or system that does some or all of what we want our design to do, we use the process of dissection in order to:

Identify in detail just how it works so we can then apply what we learn to our own design problem.

Question 11

What are some reasons we may be unable to use a design that we have reverse engineered?

Answer 11

some reasons we may be unable to use a design that we have reverse engineered include the following:

• It may not do all the things we want
• It may not do the things we want very well
• It may be too expensive
• It may be protected by a patent
• It may be our competitor’s design

Question 12

Reverse engineer the DeWalt corded power drill Model D21008K into its major subsystems.

Answer 12

Question 13

Explain the process and pros and cons of enumeration.

Answer 13

Enumeration:

Process: List all of the functions that we can readily identify.

Pros: An excellent way to begin functional analysis because it leads us immediately to the basic function(s) of the device.

Cons: It may be problematic for determining secondary functions because a lot of specific engineering background might be required.

Question 14

Enumerate the functions of a juice container.

Answer 14

The functions of a juice container are:

• contain liquid
• get liquid into the container (fill and seal the container)
• get liquid out of the container (empty the container)
• close the container after opening (if it is to be used more than once)
• resist forces induced by temperature extremes
• resist forces induced by handling in transit
• identify the product

Question 15

How are the functions of containing liquid and of filling and emptying the container distinct?

Answer 15

The functions of containing liquid and of filling and emptying the container are distinct:

• Liquid is poured in before the container is sealed by a permanent top
• Emptying may be enabled by a pull tab

Question 16

When are the following functional distinction recognized?:

• Liquid is poured in before the container is sealed by a permanent top.
• Emptying may be enabled by a pull tab.

Answer 16

The following functional distinctions (i.e., between filling, containing, and emptying) emerge when we considered the container’s lifecycle:

• Liquid is poured in before the container is sealed by a permanent top.
• Emptying may be enabled by a pull tab.

Question 17

What is a functions means tree?

Answer 17

A Function-Means Tree is a graphical representation of a design’s basic and secondary functions.

Question 18

How is a functions-means tree constructed?

Answer 18

A functions-means tree is constructed as follows:

• Tree’s top level shows the basic function(s) to be met.
• Each succeeding level alternates between showing:
  
  • the means (in trapezoids) by which the primary function(s) might be implemented,
  • the secondary functions (in rectangles) necessitated by those means

Question 19

What shapes are used to represent means and secondary functions in a functions-means tree?

Answer 19

In a functions-means tree:

• the means are represented by trapezoids
• secondary functions are represented by rectangles

Question 20

Create a functions-means tree for a lighter.

Answer 20