Developing a FunctionMeans Tree What functions will the

Developing a Function-Means Tree What functions will the design have? By what means will those functions be achieved? Taken from engineering design: a project-based introduction by dym & little

It helps to go beyond the terminology and to know what you’re really trying to do. • Think of the “functions” as what you must do. • Think of the “means” as how you might do it. • The Function-Means Tree is a tool for listing the primary functions of a design and various means of achieving those functions. • The Function-Means Tree should flow out of the Attributes List, PCC, Objectives-Constraints Tree, and Design Specifications.

Before you start too far down the path of “brainstorming” various design alternatives… • Determine the primary functions that are required. – Show these on the top level of the tree • List various means by which each function may be implemented. – Show these on the next level of the tree • Determine secondary functions that would result from implementing each of the means. – Show these on the next level of the tree • The tree continues to alternate between means and functions until you reach a reasonable termination point.

Here is a partial Function-Means Tree for a cigarette lighter. IGNITE LEAFY MATERIALS Primary function Secondary functions Electrically Heated Wire Convert electricity to heat Generate electric current Apply heat to leafy materials Focused Sunlight Protect users from post-usage burns Laser Possible means of achieving the primary function Flame Store fuel Control flame Supply fuel for flame Ignite fuel Butane Miniature heat pump Wall-outletbased system Control electrical current Battery-based system Store electricity Gasoline Resistive wire Spark Electrical resistance Secondary means Convert chemical energy to electrical current Protect electric current from flame Tertiary functions Generate electric current Function Means