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Cause & Effect Diagram The 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.

Cause & Effect Types

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Page 1: Cause & Effect Types

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.

Page 2: Cause & Effect Types

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.

Page 3: Cause & Effect Types

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

Page 4: Cause & Effect Types

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

Page 5: Cause & Effect Types

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