error proofing

ERROR PROOFINGERROR PROOFING

Quest

1/19/99 © Johnson Controls, Inc. errorprf.ppt2

Objectives:Objectives:By the end of this Workshop, be able By the end of this Workshop, be able

to….to….

• Identify 3 approaches to inspection….• Identify specific conditions that provoke errors

(Red Flags)….• Use Source Inspection to prevent defects….• Name error-proofing devices and applications….• Implement Error-Proofing in your workplace….


LogisticsLogistics

• Start/End Times• Participation• Lunch Area/Timing• Meeting Location(s)• Restroom(s)• Telephones, Messages,

Pages• Call in Number• Refreshments• Timekeeper


3 Basic Principles3 Basic Principles

• Error Proofing is AchievableZero Tolerance For Waste

• Stable Production Environment (eliminate Operator/machine possible

error)

• Customer “Pull” Drives Production


Continue to be defined by customers

Will be less of a competitive advantage

Will be ‘taken for granted’ (expected)

Will require routine use of Quality tools

Will require more creativity

What will Quality be in the 21What will Quality be in the 21stst Century?Century?


Error Proofing MeansError Proofing Means“Zero Tolerance for Waste”“Zero Tolerance for Waste”

• Fundamental belief that all errors, and the defects they cause, can be prevented = zero waste!

• Waste of correction/rework is reduced

(You MUST believe this for Poke Yoke to work)


EVIDENCES

AT&T Power Systems reduced outgoing defects by 70% (Won Deming Prize)

TRW reduced customer PPM’s from 288 to 2

Washing machine drain pipe assembly line produced 180,000 units, in 6 months, with 0 defects.

Your experiences?

Source: Productivity, Inc.


Error Proofing Means Error Proofing Means “Stable Production “Stable Production

Environment”Environment”

• An error-proofed process is repeatable..

• An error-proofed process is predictable

• An error-proofed process is stable.• An error-proofed process produces

higher quality product.

Repeatable

Predictable

Stable

Leads to Higher Quality


Error Proofing Supports Error Proofing Supports ““Customer Pull’Customer Pull’

• An error-proofed process “gets it right the first time” more often.

• Improved flexibility to respond to customer demands.

• Improved quality reduces the wastes associated with “inspecting quality into the product.”

• Inspection done @ source


Error Proofing OpportunitiesError Proofing Opportunities


Error Proofing (Poka-Yoke)Error Proofing (Poka-Yoke)

• Improves product quality and ensures consistent process results.

• Emphasizes designing the manufacturing process to ensure zero defects.

• Requires disciplined problem-solving and beliefs that defects are not inevitable in production shops.

• Is effective when done in teams.


• Name some products, services where you are used to receiving high quality every time....

• Any bad product or service experiences?

• Are high quality products achievable every time?


How Can We Ensure QualityHow Can We Ensure Qualityin the Following Areasin the Following Areas??

ManMaterialMachineMethod

Information(4M + I)


5 Elements of Production5 Elements of Production

1. MeControl: Discipline, Fundamental Education, Cross-Training Assignments

2. MaterialControl: Source Controls

5. InformationControl: Visual Controls (Instruction Sheets, Kanban)

4. MethodControl: Assembly Line & Work Standards

3. MachineControl: Conditions Assured Through Poka-Yoke & Everyone's Participation


Inspection TechniquesInspection Techniques

Judgement (inspection) Informative (inspection) Source (inspection)

Remember Shaving?


Judgment InspectionJudgment Inspection

“Then and

There”


Informative InspectionInformative Inspection

• Feedback provided to upstream processes when defects are discovered.

• Uses statistics and sampling.• Seeks to minimize defects.


Informative InspectionInformative Inspection


Source InspectionSource Inspection

• Operations examined for conditions that may breed defects.

• Emphasis on data collection and problem solving.

• 100% inspection built into each operation.


Self-Checking for ErrorsSelf-Checking for Errors

• Work verified before it leaves station• Build sensory + visual aids into operation• Represents 100% source inspection• Workers responsible to implement

quality control• Standards must be followed for success

(Builds out Operator Error)


Self-Checking for ErrorsSelf-Checking for Errors


Successive Checking for ErrorsSuccessive Checking for Errors

• Users of upstream work verify part or process for correctness before use

• Prevents cumulative errors• Builds teamwork between operations.


Successive Checking for ErrorsSuccessive Checking for Errors


Defects vs. ErrorsDefects vs. Errors

• Analyzing the production process to achieve zero defects = Distinguishing between defects and errors

• Defects = results (effects of mistakes )

• Errors = sources (causes of mistakes)


Error Defect

Not tightening lug-nuts Loose metal

Setting too dark on toaster Burnt toast

Failing to clean metal Dirt in paint

Some Common Some Common Manufacturing ErrorsManufacturing Errors

Quest


Most CommonMost CommonManufacturing ErrorsManufacturing Errors

• Omitted processing• Processing errors• Workpiece setup• Missing parts• Wrong parts• Processing wrong workpieces• Misoperation• Adjustment errors• Improper equipment set-up • Tools & jigs improperly

prepared

Why Do People Why Do People Make Mistakes?Make Mistakes?

Quest


Most Common Human ErrorsMost Common Human Errors• Forgetfulness - Lack of task priorities• Misunderstanding - Lack of familiarity with

process• Identification - Misreading visual cues• Poor training - Lack of experience,

reinforcement• Intentional - Deliberate mistake• Willful - Ignoring rules without

harmful intent• Inadvertent - Unaware of mistake• Slowness - Delays in judgement or

physical ability• Poor Supervision - Unclear, contradictory

instructions• Surprise - Errors due to abnormal

events


Manufacturing & Human ErrorsManufacturing & Human Errors

• Common human errors can be eliminated through process design

• Defects are not inevitable• You can achieve Zero Defects!


Red FlagsRed Flags(When These Things Happen…)(When These Things Happen…)

* Adjustments* Tooling/tooling change* Dimensionality/specification/critical condition* Many parts/mixed parts* Multiple steps* Infrequent production* Lack of or ineffective standards* Symmetry* Asymmetry* Rapid repetition* High volume/extreme high volume* Environmental conditions


AdjustmentsAdjustments

Having to bring parts, tools or fixtures into a

correct relative position only by

sight or feel.

reference pin divergence

correct incorrect


Tooling/Tooling ChangeTooling/Tooling ChangeDefects From Malfunctions or Incorrect Defects From Malfunctions or Incorrect

ToolingTooling

glue

holder

laminated surface

Spots


Dimensionality/Specification/Dimensionality/Specification/Critical ConditionCritical Condition

Relying solely on Operator

skill for proper job setup or

precision work


Many Parts/Mixed PartsMany Parts/Mixed Parts

Operations without safeguards to prevent use of

incorrect parts


Multiple StepsMultiple Steps

Work requiring many small

operations or sub-tasks


Infrequent ProductionInfrequent Production

Intermittent operations, or

production


SymmetrySymmetry

Model X

Condition that allows parts to be installed upside

down or in mirror image

position


AsymmetryAsymmetry

Where opposite sides of a part, tool or

fixture look identical but can only be used correctly one way.

pointer boss

washerpointer

bottom die has a flat surface


Rapid RepetitionRapid Repetition

From Automatic Welding Machine

Next Process

Shaft Omitted

Repeating the same work over and over so that errors are not readily

detected


High VolumeHigh Volume

Operations where output is large & fast so that errors escape visual

inspection

right side up upside down

workpiece


EnvironmentEnvironment

wire stock

reel stand

dimensional variation

tension device

to machine

foreign matter

Physical conditions around the workplace that can adversely impact quality


Red Flag Conditions

Operation

S S

CommentsAdjustments

Tooling Concer

ns

Critical S

pec Condition

Mixed Parts

Multiple S

teps

Infrequen

t Producti

on

Lack of S

OP

Symmetry

Asymmetry

Rapid Repitition

High Volume

Environmen

tal Conditio

ns


Quality Data ReviewQuality Data Review

• Review top 3 quality issues (in dollars or PPM) in our area for the previous month.

• Review top 3 quality issues (dollars or PPM) in our area for the previous 3 months.

• Determine which errors reoccur.


Production Shop ExerciseProduction Shop Exercise(60 min.)(60 min.)

• Form teams.• Decide on line/area to review.• Review operation(s) to Red Flag, using standard

form.• Consolidate ideas into groups.• Present for discussion.


Team DebriefTeam Debrief

• Describe Red Flag Conditions Found in Your Area.

• How Do These Conditions Affect Quality?


Implementation of Error-Implementation of Error-ProofingProofing

• Identify product defect & collect data• Track defect at:

– Point Discovered– Point Created

• Review SOP at defect creation point• Identify any deviations from SOP• Identify Red Flag condition at creation point• Implement error-proofing device to prevent

error or defect• Check results & make process adjustments


Describe Product Defect & Collect Describe Product Defect & Collect DataData

Problem: Missing Nut Bracket Screws

1 2 3 4 5 6 7 80

5

10

15

20

25

Hour

Defects

Are You Capturing This Information?


Identify Two Key LocationsIdentify Two Key Locations

Defect creation & discovery

points


Review SOP atReview SOP atCreation PointCreation Point

Is there an SOP? Deviations?

Service Manual

I've been using Phillips head

screws!

I've been using slot head screws!


Error-Proofing DevicesError-Proofing Devices

• Level 1 (Prevention: Ideal!) Eliminate error at the source

• Level 2 (Detection) Detects errors in the process of occurring, before it has become a defect

• Level 3 (Detection) Detects a defect after it has been made but before it leaves the station


Prevent Defects by:Prevent Defects by:

• Shutdown (Level 1) - Processing stopped until error is

corrected.

• Controls (Level 1)- Only allowing parts to fit into jigs,

fixtures in the correct position.


Error & Defect DetectionError & Defect Detection

•Error Detection (Level 2)– Detects errors as they are being

made.

•Defect Detection (Level 3) – Detects defects before they leave

station.


Common DetectionCommon DetectionFunction & DevicesFunction & Devices

Detection Functions DevicePressure gauges, pressure-sensitive switchesTemperature thermometers, thermostats,

thermistors, thermocouplesElectric Current meter relays, current eyesVibration vibration sensorsCycles counters, stepping relays, fiber

sensorsTime times, delay relays, timing units,

time switchesInformation buzzers, lamps, flashing lamps


Error-Proofing Devices:Error-Proofing Devices:Visual DevicesVisual Devices


JigsJigs

Limit Switch

Desired Drilled Holes

Groove

Groove

Jig

IncorrectWorkpieceL/S

CorrectWorkpieceL/S


Photoelectric Devices & OpticsPhotoelectric Devices & Optics


Contact DevicesContact Devices


CountersCounters

0 0 0 0 0 4


ChecklistsChecklists

Packing Checksheet

Hubcap Covers (4)

Owner's Manual (1)

Radio Manual (1)

Floor Mats (4)

Tire Manual (1)

Plant Decal (1)


Shop Floor ApplicationShop Floor Application

• Describe defect (error). (Write it down, draw it, etc.)

• Plot defect rate. (Pareto charts, histograms)

• Identify where defect is discovered and made• Detail SOP (What is SOP here?)• Identify deviations from SOP• Identify causes for deviations (Fishbone?

Brainstorming?)• Identify Red Flag conditions• Identify source errors• Propose ideas to eliminate or detect errors• Propose possible error-proofing devices


SummarySummary

• Zero defects are possible if you build 100% inspection checks into every process.

• The production process can be designed to prevent & detect human errors.

• Team skills facilitate error-proofing.


SummarySummary

• Source inspection & successive checking are the foundations of error-proofing.

• Error-proofing should be considered where an operation contains Red Flags.

• Error-proofing devices need not be expensive or high-tech.


HAVE FUN!

error proofing

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