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BLOW OUT
ROCK
FLAT TYRE
MECHANICAL FAILURE DRIVER ERROR
BRAKEFAILURE
STUCKACCELERATOR
BROKEN TIEROAD POOR
TRAINING
RECKLESS
POORREFLEXES
CHEMICALLY IMPAIRED
SLEEPY
LOST CONTORL OF CAR
NAIL
RAIN
ICE
SLIPPERY ROAD
OIL
SNOW
BLOW OUT
ROCK
FLAT TYRE
NAIL
GLASS
WORN PAD
FLUID LOSS
POSSIBLE CAUSES OF LOST CONTROL OF CAR
Cause & Effect DiagramThe output or result of a process can be attributed to a multitude of factors, and a cause-and-effect relation can be found among those factors. We can determine the structure or a multiple cause-and-effect relation by observing it systematically. It is difficult to solve complicated problems without considering this structure, which consists of a chain of causes and effects, and a Cause-and-effect diagram is method of expressing it simply and easily.
Kauro Ishikawa introduced the Cause and Effect (CE) diagram in Kawasaki Iron Works in 1943. Though it also known as Ishikawa Diagram and Fishbone diagram, the term Cause and Effect is self explanatory.
A simple cause-effect diagram is shown below. The phenomenon to be explained is “Lost control of car”. Some of the possible major factors contributing to that lost control are a flat tyre, a slippery road, mechanical failure, and driver error. Each of these major categories of causes may, in turn, have multiple causes. A flat tyre may come from a nail, a roack, glass, or a blow-out from material failure. The causal relationship can be traced back still more step in the causal chain if necessary or appropriate. Lost control may arise from a mechanical failure; that failure may be a brake failure, which, in turn, may come either from fluid loss or from worn pads. You can probably think of other factors to add to this diagram.
As we can see from figure, this tool has three prominent basic features:
It is a visual representation of the factors that might contribute to an observed phenomenon that is being examined.
The interrelationships among the possible causal factors are clearly shown. One causal factor may appear at several places in the diagram. For example, if temperature affects both moisture content and physical dimensions, then temperature would appear in both places.The interrelationships are generally qualitative and hypothetical. A CE diagram is usually prepared as a prelude to developing the data needed to establish causation empirically.
The most important consideration in the construction of Diagram is clear understanding of the Cause-Effect relationship.
All possible sources of causation need to be considered.1. Objects – Machines and Material….2. Conditions - Motivations, temperature..3. Timed sequence in the process - time of the day, sequence in production4. Place – production line, distributor, branch office.
These are what, why, when and where (4 W) of cause and effect.
How to construct Cause-and-Effect diagram 1. Define clearly the effect or symptom for which the causes must be identified.1. Place the effect or symptoms being explained at the right, enclosed in a box. 2. Draw the central spine as a thick line pointing to it.3. Use brainstorming or rational step-by step approach to identify the possible causes.4. Each of the major area of causes (not less than 2 and normally not more than 6) should be
placed in a box and connected with the central spine by a line at an angle of about 70 degree)5. Add causes for each main area.6. Add subsidiary causes for each cause already entered.7. Continue adding possible causes to diagram until each branch reaches a root cause.8. Check the logical validity of each causal chain.9. Check for Completeness.
Three types of C& E Diagram
1. Dispersion Analysis Type :
The Dispersion Analysis Type of CE diagram is constructed by repeatedly asking the question, why does this dispersion (or scatter) occur? Its strong point is that it helps organize and relate factors that cause variability is products and other process outcomes. Its weak points are that the form of resulting diagram is dependent on the views of the people making it and that small causes may not get isolated or observed.
2. Cause enumeration type: The cause enumeration type of CE diagram is generated by listing all possible causes and organizing the causes to show their relationships to the aspect of product or process quality that is being examined (Ishikawa 1986). This type of CE diagram can also be produced in brainstorming sessions where principal categories such as manpower, materials (inputs), methods, and machinery (tools) are used to prompt probing questions that uncover possible causes. The completed diagram may end up looking much like one produced by the dispersion analysis process, but it may not. The thought process used to generate cause enumeration type diagram are (and should be) more free-from and less constrained than for dispersion analysis type CE diagram. The strength of the Cause enumeration type is that enumerating large numbers of likely causes reduces the probability of overlooking a major problem area. When done well, this tends to give a more complete picture in comparison to Dispersion Analysis Type. The weakness is that it may be hard to relate the twigs of the tree to the end result, which can make the diagram difficult to draw and interpret.
3. Production process classification type
Production process classification type of CE diagram is constructed by stepping mentally through the production process. This may be done in one of the two ways : (1) by making the steps in the process the major ribs of a fishbone diagram or (2) by superimposing boxes on the backbone so that each box
Typing Errors
(mistyping)
Person Requesting Typing
Manuscript
TypewriterTypist
Understanding ofMaterial
Omissions
Fitting Material
Location
Size
Type of ink
WritingMaterials
ThicknessOf nib
Layout
Instructions
Format
Checking of MemoDictation
Pronunciation
RepairsMaintenance
Servicing
Distance from Typist’s Body
Physical Condition
Height
Errors
Handwriting
Experience
Preliminary Checks
Quality
Paper
Colour
SpeedTechnique
PausesRhythm
Eyesight
Physical Condition
Physical Fatigue
Working Environment
Conversation
Interruptions
Answering Telephone
Other Jobs
Brightness
Lighting
Location ofEquipment
Ringing of Telephone
Noise
Type of Pen
Size
Style
Attending to Visitors
Colours
FLUX
CONVEYOR SPEED
EXHAUST
SOLDERMACHINE
SPECIFICATION COMPONENTS PRINTED WIRE CARD
VALIDITY
DROSS
TEMPERATURE
LOW HIGH SPEED
INTERPRETATION WEIGHT
TARMASKING
STORE MASKTYPE
Possible Causes of Solder Defects
AIR SUPPLYCONTAMINATION
SPECIFIC GRAVITY
ACTIVITY
STORAGE
AMOUNTSO
LDER
DEF
ECTS
PRE HEAT
AIR SUPPLYCONTAMINATION
MAINTENANCE
CONTROLLER
ANGLE
FLUDITY
CONTAMINATION
ALLOYUNEVEN WAVE
WAVE HEIGHTWAVE DYNAMIC
CONTACT TIME
INCOMING SOLDER CONTAMINATION
TEMPERATURE
TIME
WRAPPEDOUTGASSING
PAD GEOMETRYSTORAGE
FLUDITY
DROSS
TEMPERATURE
ORIENTATIONGEOMETRY
CONTAMINATEDLEADS
LENGTH
SOLDERABILITY
MOVEMENT
PLACEMENT
METALLURGYOF LEADS
is a step in the production process. When the process steps are displayed along the backbone as illustrated in example given below., the causes are depicted on lines (ribs) that feed into either a box or one of the backbone segments that connects sequential boxes. The strength of this type of diagram is that it is easy to assemble and understand. The weaknesses are that similar causes often appear in more than one place and that problems resulting from combinations of more than one factor are difficult to illustrate.
PISTON
& PISTO
N R
ING
S R
EJECTIO
N
PISTON SUPPLY PISTON SUB ASSEMBLY ASSEMBLY WITH ENGINE (STAGE NO. 11 )
CRANK SHAFT SUB ASSEMBLY
PRODUCTION PROCESS CLASSIFICATION TYPE
OPERATORPISTON UN PACKING
WORK LOAD
OVERCONFIDENCE
BIN
SIZE
EDUCATIONILLITRATE
UNSUFFICIENT
HIGH PRODUCTION
AWRAENESS
NEGLIGENCY
LACK OF MOTIVATION
BEHAVIOUR
SKILL
NO INSPECTIONEXPERIENCE
PISTON SUPPLY
SUPPLY TO SUB ASSEMBLY
DAMAGE
BINNING AFTER UNPACKING
NO GAP BETWEEN PISTONS
BINFLAT SURFACE
WORKING TABLE
SPACE
DESIGN
TRANSPORTATION
TROLLY
OVERLOADING
DESIGN
STRIKING
DESIGN
Whatever method you use for producing CE diagram, be on the lookout for the diagrams with many major ribs and few twigs. This almost always indicates either that the understanding of the process was shallow or that the diagram is too generalized. Use care also when a diagram lists only five or six causes. This kind of diagram is usually inadequately penetrating , even though its form may be correct
ASSEMBLY PROCEDURE
LOCK FITMENT
BEND
PIN GROOVE
FALLING ON FLOOR
WORKING TABLE
PISTON SUB ASSEMBLY
BINNING
SIZEOVER
UNDERWORN OUTHIGH PRODUCTION
INSPECTION
PISTON RING
HARDNESSLESS
MORE
MISMATCHING
IDENTIFICATION MARK
SIZE VARIATION
~`T “ MARK POSITION
TOOL DAMAGE
STRIKING
OVERLOADING
DOUBLE STORY
BROKEN
DAMAGE
RING EXPANDOR
HANDLING
OVERLOADINGWORK IN HURRY
MISHANDLING
HIGH MOVEMENT
DESIGN
THICKNESS
LESS
MORE
VENDOR