Function Based Design

8/3/2019 Function Based Design

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PProductroduct DDesign andesign and PProductionroduction SSystemsystems LLaboratoryaboratory

Interdisciplinary Capstone DesignWeek 10

:

Function-Based Design


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Function-based design Overview

A structured and systematic approach to engineeringdesign (Pahl & Beitz)

Conceptual design < Solution neutral term

Feature/Geometry < Functionality

Hierarchy Various levels of function-abstraction


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What is Function?

What the product must do

Logical flows of energy, material, or informationbetween objects or the change of state of an objectcaused by one or more of the flows

Function/Flow of energy: type of energy and action

Function/Flow of materials: through-flow, divergingflow, converging flow

Function/Information flow: mechanical/electricalsignals, software


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Function Analysis Overview

Express the overall function withthe conversion of inputs into outputs

Break down the overall function intosub-functions

Draw a block diagram showing the interactionsbetween sub-functions

Draw system boundary

Search for appropriate components to performsub-functions and interactions


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Function Analysis - Procedure

Step 1: Express overall function Black box representation in terms of inputs and outputs

As broad as possible at first narrowed down later

BLACK BOX

Inputs Outputs

Function


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Step 2: Break down overall function Create a set of essential sub-functions

Express with a statement of a verb and a noun

As specific as possible

Inputs/outputs of sub-functions compatibility

Overall function Sub-function 3

Sub-function 2

Sub-function n

Sub-function 1


7/18PProductroduct DDesign andesign and PProductionroduction SSystemsystems LLaboratoryaboratory


Step 3: Draw a block diagram Order and link sub-functions appropriately

Black box Transparent box

Different convention for different types of I/O flows;energy, materials, information

Sub-function

Sub-function

Sub-function

Sub-function

Inputs

Function

Transparent box




Step 4: Draw the system boundary Define precise extent and location of the system

boundary

Possibly narrow the boundary to define a feasibleproduct

Depends on management policy and client requirements

Step 5: Search for suitable components

Depends on nature of product or device to be designed Consider many alternative components



Function Analysis - Example

Black box model of a power screwdriver

Overall function Inputs Outputs

Design example: Power screwdriver Step1: Express overall function



Function Analysis - Example

Step2 & 3 & 4

Functional model of a power screwdriver



Functional Basis Approach

Definition ofFunctional Basis A standard taxonomy of function and flow in an attempt

to formalize the representation of functional abstraction

Objectives

To develop universal design language allowing designers

to communicate product function efficiently

Impact

Product architecture development, Systematic functionstructure generation, Archival and transmittal of designinformation, Comparison of product functionality,Creativity in concept generation, Product metrics,robustness, and benchmarks

Proposed by Stone & Wood (1999)



Reconciled Functional Basis Flow Set



Reconciled Functional Basis Function Set



Case Study: Tree Tagger



Case Study: Humidifier

Black-box Model

humidifyroom

Electricity Noise, Heat

Water Vapor

On/Off Humidity

Energy flow Material flow Signal flow



Case Study: Humidifier

Functional basis modeling

importelectricity

convert EEto TEee

ee

on/off

dissipateAE

ae

importliquidwater

storeliquidwater

guideliquidwater

transmitTE

water

te

convertliquid to gas

water

te

guidegas

vapor

dissipateTE

te

exportgasvapor

vapor

humidity

heat

noise



Case Study: Gripper

Black-box Model

Energy flow Material flow Signal flow

graspobject

Electricity Noise, Heat

Object Object

On/Off

Position/Orientation Position/Orientation



Case Study: Gripper

Functional basis modeling

importelectricity

convert EEto MEee

ee

on/off

dissipateAEae noise

coupleTRE & RE

tre

re

allowDOFtre+re

importsolidobject

positionsolid

object

pos./orient.

transmitTRE + RE

tre+re

object

pos./orient.

secureobject

meobject

pos./orient.

object

pos./orient.

dissipateTEte

heat

Documents

Function Based Design