MST326 3 Problem

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25 January 2007 MATS326-3 problem.ppt

Problem Solving

Techniques

MST326 lecture 3




Outline of lecture

BrainstormingMind maps

Cause-and-Effect diagrams Failures Mode and Effects Analysis Fault Tree Analysis

Design of Experiments




Brainstormingproposed by Alex Osborn³for the sole purpose of producing checklists of ideas´technique to identify causesand develop solutions to problems³seeking the wisdom of ten peoplerather than the knowledge of oneperson´ [Kaizen Institute]




Brainstorming

no criticism is permittedo ³only stupid question is one that is not asked´ [Ho]

wild ideas are encouragedo often trigger good ideas from someone else

each person contributes one ideao further single ideas on second circuito repeat until no further ideas

all contributions are recorded in view




Brainstorming

Osborn proposed 75 fundamental questionscan be reduced to:

seek other uses? adapt?modify? magnify?minify? substitute?rearrange? reverse?combine?



TRIZTeorija Reshenija Izobretatel'skih Zadach

loosely translates asTheory of Inventive Problem Solving (TIPS)

40 Inventive Principles




40inventive principles of TRIZ

IP 01 : Segmentation IP 0 2: Taking out IP 0 3: Local qualityIP 04 : Asymmetry IP 0 5: Merging IP 0 6: UniversalityIP 0 7: Nested doll IP 08 : Anti-weight IP 09 : Preliminary anti-action

IP 10 : Preliminary action IP 11 : Prior cushioning IP 1 2: EquipotentialityIP 1 3: The other way round IP 14 : Spheroidality or curvature IP 1 5: D ynamicsIP 1 6: Abundance IP 1 7: Another dimension IP 18 : Mechanical vibrationIP 19 : Periodic action IP 2 0 : C ontinuity of useful action IP 2 1 : Rushing throughIP 22: B lessing in disguise IP 23: F eedback IP 2 4 : IntermediaryIP 25: Self-service IP 26: C opying IP 27: C heap short-lived objects

IP 2 8 : Mechanics substitution IP 2 9 : Pneumatics and hydraulicsIP 3 0 : F lexible shells and thin films IP 3 1 : Porous materials IP 32: C olour changeIP 33: Homogeneity IP 3 4 : D iscarding and recovering IP 35: Parameter changeIP 36: Phase transition IP 37: Thermal expansion IP 3 8 : Strong oxidantsIP 3 9 : Inert atmosphere IP 40 : C omposite materials





Mind maps

attributed to Tony B uzano classic book ³Use Your Head´




Mind maps

Image from http://www.loanedgenius.com/scrabble_2_letter_words.gif




Cause-and-Effect diagrams

Cause-and-Effect diagramo often referred to as a fishbone diagramo or an Ishikawa diagram

introduced by Kaoru Ishikawao simple graphical method to record and

classify a chain of causes and effects inorder to resolve a quality problem




Cause-and-Effect diagrams

C larify the object effectPick causesDetermine the priority causesWork out the counteractions

for priority causesimplement appropriate solutions toeliminate or reduce the causes of problems




Cause-and-Effect diagrams IC larify the object effect

o a numerical measurement should beestablished against which subsequentimprovement can be judged




C ause-and-Effect diagrams IIPick causes

create a team of people to brainstormpossible causes that may lead to the effect

study the actual effect in the problem environment

on a horizontal line draw diagonal branchesfor direct causes of the effect

using arrows onto the branches createsub-branches for appropriate secondary causesconfirm all elements of the diagramare correctly positioned

quantify the causes wherever possible




Cause-and-Effect diagrams IIIDetermine the priority causes

o analyse any existing data for the problemo if practical, create a Pareto diagram.o otherwise, determine a ranking of the

relative importance of each cause.




Cause-and-Effect diagrams IVWork out the counteractions

for priority causeso put in place appropriate solutions

to eliminate or reducethe causes of problems




Cause-and-Effect diagram:

Image from

http://www.ifm.eng.cam.ac.uk/dstools/gif/ishika.gif




Failures

Mode and Effects Analysis

FMEA iso a useful tool for reliability analysiso systematic check of a product or process

functionfailure causes

failure modesfailure consequences




Failures


Requires a thorough knowledge of o functions of the componentso contribution of those components

to function of the system For every failure mode at a low level,

failure consequences are analysed ato the local levelo the system level




Failures


FMEA is usually qualitativebut may also be quantitative

initiated during planning and definitionof a project to investigate qualitativereliability demands of the market

during design and development, for quantitative reliability activities



25 January 2007 MATS326-3 problem.ppt Table From Evans and Lindsay Chapter 13




F ailures M ode and Effects Analysisdesign- F MEA for design reviews

o definition and limiting of the systemo choice of complexity level

o check of component functionso check of system functionso identification of possible failure modeso identification of consequences of failureso possibility of failure detection and failure localisationo assessment of seriousness of failureo identification of failure causeso interdependence of failureso documentation






F ailures M ode and Effects Analysis

Process- F MEA for o pre-production engineeringo design of process controlo process improvement

FMEA is efficient where component failureleads directly to system failurefor more complex failures, F MEA may besupplemented by F ault Tree Analysis ( F TA)




Some URLs for FM

EAhttp://www.fmeainfocentre.com/http://supplier.intel.com/ehs/fmea.P DF

http://www.cs.mdx.ac.uk/puma/wp 18 .pdf http://www.sverdrup.com/safety/fmea.pdf http://www.uscg.mil/hq/msc/fmea.doc

http://www.competitiveedge.net/pdfs/fmea.pdf http://www.fmeca.com/ffmethod/methodol.htmhttp://www-personal.engin.umich.edu/~wmkeyser/ioe53 9 /fmea.pdf

http://www.engin.umich.edu/class/eng 401 /00 3/LC Notes/fmea.pdf




F ault Tree AnalysisLogical chart of occurrences

to illustrate cause and effectsdeveloped by DF Haasl, HA Watson,

BJ F ussell and WE Veselyinitially at B ell Telephone Laboratories

then North American Space Industry




Fault Tree Analysis

Common symbols used 1

o main evento basic evento incompletely analysed evento restriction




Fault Tree Analysis

Common symbols used 2

o or-gate

o and-gate

o transfer to or from another place

&

u 1+



25 January 2007 MATS326-3 problem.ppt Figure From Evans and Lindsay Chapter 13




Design of Experimentsoriginally conceived by

Ronald Aylmer F isher at Rothampstead Experimental Stationduring the 19 20 s

o analysing plant growing plotsunder different conditions, andneeded to eliminate systematic errors.

Image from http://www.csse.monash.edu.au/~lloyd/tildeImages/People/ F isher.RA/




Exper im ental d es ig nRandomisationReplication - repetition

so that variability can be estimated Blocking - experimental units in groups

(blocks) which are similar Orthogonality - statistically normal.

Use of factorial experimentsinstead of one-factor-at-a-time




Design of Experimentsfull factorial experiment

o where a number of factors

may influence the output of a process,it is possible to study all combinationsof levels of each factor

o if the number of factors considered increases,

then number of experiments requiredincreases more rapidly.






Design of Experimentsresults plotted to indicate the influence of each of the factors studiedwhen one factor affects the response,this is known as the main effect .when > 1 factor affects the response,this is termed an interaction .




Design of ExperimentsG enichi Taguchi developed orthogonal arrays

fractional factorial matrixpermits a balanced comparisonof levels of any factor with a reduced number of experiments.each factor can be evaluated independentlyof each of the other factors.




Orthogonal arrays

L4 : three two-level factorsL9 : four three level factors

Arrays from http://www.york.ac.uk/depts/maths/tables/orthogonal.htm




C ommon orthogonal arrays

Array Levels EquivalentF ull F actorialL4 3 x 2 8

L8 7 x 2 1 28

L9 4 x 3 81

L12 11 x 2 2 048

L16 1 5 x 2 32 76 8

L25 6 x 5 1 5 625L27 1 3 x 3 1 594 323

T able from T ony Bendell T aguchi Methods , 1989




Taguchi Quality Loss F unctionL(x) = k ( x - t ) 2

o L = the loss to societyof a unit of output at value x

o t = the ideal target value

o k = constantas non-conformance increases,losses increase even more rapidly

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MST326 3 Problem