PokaYoke

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Poka-Yoke
Douglas M. Stewart, Ph.D. Anderson Schools of
Management University of New Mexico
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Zero Quality Control

• Started in the factory
• Refined by Shingo at Toyota
• Involves 100 Informative inspection
• Uses simple devices and procedures called
  poka-yoke
• Photo sensors
• Trip switches
• Fixtures to orient parts
• Checklists
• Kitting of parts

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When to Inspect
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Additional Inspection Points

• Where raw material is received
• Prior to costly operations
• Prior to potential damage
• Prior to point of no return
• Prior to stocking
• Where quality responsibility changes hands

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How are errors detected?

• Self monitoring
• Checking by others
• Environmental cues
• The primary objective of a poka-yoke
• Warning vs. Control

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Doing the Poka-yoke

• Poka-yoke (From the Japanese, yokeru to
  prevent, and poka inadvertent errors.) Simple,
  inexpensive, failsafe devices or systems which
  prevent mistakes from being made or from becoming
  defects.

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What do you failsafe?
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Poka-yoke Classification

• Classification based on what is fail-safed

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• Classification based on fail-safing method
• Physical detection and control (contact methods)
• Identify items by their physical characteristics
• Sequencing (motion-step methods)
• Indicate, discourage or prevent deviation from
  process steps
• Grouping and counting
• Assure correct groupings, ordering, and the use
  of all and only the correct components
• Information enhancement
• Prevent failed or incomplete communications as
  well as enhance existing communications

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Provider Errors

• Task Errors
• Doing the work incorrectly
• Doing work not requested
• Doing work in the wrong order
• Doing work too slowly
• Treatment Errors
• Not acknowledging the customer
• Not listening to the customer
• Not reacting appropriately to the customer
• Tangible Errors
• Failure to clean facilities
• Failure to control noise
• Failure to proof documents for content and
  presentation

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Customer Errors

• Preparation Errors
• Failure to bring necessary materials to the
  encounter
• Failure to understand role in the service
  transaction
• Failure to engage the correct service
• Encounter Errors
• Failure to remember steps in the service process
• Failure to follow system flow
• Failure to specify desires sufficiently
• Failure to follow instructions
• Resolution Errors
• Failure to signal service failures
• Failure to learn from experience
• Failure to adjust expectations appropriately
• Failure to execute appropriate post-encounter
  actions

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Fail-safing the Customer

• Preparation for the encounter
• DEC service flier
• During the encounter
• Locks on airline doors activate lights
• Resolution of the encounter
• Outlines for toys on floor of child care center

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DEC Service Flier
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Fail-safing the Server

• Task
• Operating room trays with indentations for
  instruments
• Treatment
• Smile checklist (greeting, taking order,
  informing of desert special, and giving change)
• Tangibles
• Mirrors for personal appearance inspection
• Chairs with armrests to prevent sleeping

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Physical Detection and Control Methods

• Orientation and placement
• Delimiting and controlling the physical space
• Lock-outs, and lock-ins
• Go / no-go gauging
• Dispensers
• Detecting presence or absence
• Improved visibility
• Unusual physical attributes

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Examples
 
Guide Pins and Cutouts (that limit orientation)
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Examples (cont.)
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Examples (cont.)
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Examples (cont.)
 

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Examples (cont.)
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Sequencing Methods

• Baiting
• Task substitution
• Interlocks

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Examples
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Examples (cont.)
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Grouping and Counting Methods

• Counting and ordering
• Arrangement
• Kits
• Layout mats
• Checklists

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Examples
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Information Enhancement Poka-Yokes

• Moving information through time
• Storing it for later use
• Consolidating it to get the big picture
• Prediction
• Moving information across space
• Making information stand out

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How do you Fail-safe?

• Educate the team about poka-yoke devices
• Find the source of the errors
• Blueprint (flowchart)
• Find defects
• Trace to source
• Brainstorm
• Inexpensive, clever devices
• Only one device per error
• Toyota averages 12 per machine
• Type of Cue
• Warning
• Control
• The 50-50 rule

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Fail-safing works best when

• There is a fixed sequence of operation that are
  routinely followed
• Each operation has clearly identifiable goals and
  specifications
• The number and range of inputs you must control
  for each operation is small
• The customer knows the drill in general terms
  at least
• Task and tangibles rather than treatments are the
  core features of the service
• The process design must be fundamentally sound