ME-310 Mechanical Design: Introduction

Functional Decomposition

Find the overall function to be accomplished by the product or service

• Clearly define system boundaries according to whether you will control
• Remember: Mass is conserved
• Remember: Energy is conserved
• Internal and boundary objects must be named
• If tracking information, ask what will be used to indicate performance.

Create subfunction descriptions

• Use: a box, an active verb, an acted-upon object, sometimes a modifier, flows of material, energy and control information
• Describe what is done not how it is done
• Break the function down finely
• List all alternative functions
• Show all material, energy and info flows associated with the subfunction
• Consider all operational sequences, not just the use phases
• Use standard notation when possible
• Play the role of the subcomponents to gain perspective
• For Virtual design, Redesign or Benchmark
• Disassemble the object, one component at a time
• Note which features, components, assemblies, humans, tools, etc. the removed objects interact with, the type of interaction and what material, energy or info are transferred during said interaction.
• For each component, draw the material, energy and information equivalent of a "free body diagram"

Order the subfunctions

• Flows must be in logical or temporal order
• Redundant functions must be eliminated
• Functional choices must be decided upon
• External functions must be eliminated
• Remember conservation laws