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Monday, January 14, 2013

Don’t Blame the Operator, Ask One More Why

Operator error is often used in corrective action as a cause of failure. Although operators can make errors, operator error is not an acceptable cause of failure because it is not actionable. It is very often overused by the lazy or those who don't know any better but human error can almost always be mitigated.

Processes must be designed to expect that operators wish to do the correct thing. Training and providing work instructions and procedures are not robust enough for repetitive processes. Poor training and / or work instructions are inadequate secondary choices to operator error. The real issue is the operator discovers errors made in the process design. The process designer / engineer must strive to engage operators into the process and help reduce the number of possible errors available for operators to find.

We must approach operator error by considering the interfaces of the process that the operator is engaged in. The process should be designed to permit communication between the process and the operator.

With the process interface in mind, we must ask why one more time to cascade from operator error, down to specific actionable topics. Here are some examples of these actionable topics:

Actionable Topics to Replace "Operator Error"
Work Station Design
  • Bench/Table Height
  • Organization of work tools (5S)
    • # of tools and placement
  • Component Positions
    • Quantity
    • Similarity
  • Extended Reach (occasional)
  • Lighting
  • Comfort Features
    • Foot rests/seat position
    • Standing work bench position
  • Height and Reach
    • Work type
  • Weight
    • Lifting
  • Motion
    • #of steps
    • Degrees of freedom
  • Work station interface
    • Blind operation
  • Posture
  • Insertion force
  • Static insertions
    • Plastic deformation of end source
  • Tool
    • Vibration
    • Tool design
Documentation and Training
  • Illustrations Process Documentation
    • “A4” One page
    • No Documentation
  • Validation of Standard Work Practices
    • Testing
    • Demonstration
    • Frequency of validation
  • Training
    • Definition
    • Measurement of Success
  • Complexity of documentation
  • Labeling
  • Legibility of work instructions
    • # of pages
    • Understandability (5 second rule)
    • Fonts size and type
Assists and Tool Design
  • Error proofing features (lack of)
  • Tool calibration
    • Pallet compliance
  • Correct tool
    • Multiple look alike
  • Life of tool
    • Wear out
  • Fixture control
    • Maintenance
  • Clamp pressure
    • Inadequate
    • Too great
  • Cycle completion/interruption
  • Locators / proximity sensors
    • Life expectancy
  • Measurement instrument degradation
    • Environment
Cognitive Attention and Concentration
  • Audible Noise (Interruption)
  • Environment
    • Temperature
    • Humidity
  • Sensitivity to Interruption
  • Repetition
    • Motion
  • Trance/Zone Inducement
    • Sound Quality
    • Harmonics
    • Vibration/cyclical noise

Processes designed with operators in mind provide feedback to the process status. This process interface can be passive or active. Passive interfaces use visual cues, such as seeing parts remaining in a kitted bin or tactile feedback when installing a part or engaging a clamp. Active interfaces use logic, sounds, lights, process interruption or lockouts as feedback. Ultimately, Poka Yoke (error and mistake proofing) are deployed in order to eliminate or reduce errors discovered by operators.

Operator error is not actionable but the causes of operator error can be addressed by process and product changes. Don’t take the easy way out and blame the operator. Ask why, and then improve the process. Show Respect for People.

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1 comment:

  1. If you answer is that a person was at fault, I would even ask why several more times. Another question to ask is why were they allowed to do so? Why was it so easy for them to do so (if it was)? Can't we design the process to make the error much more difficult or impossible? Sometimes the process needs to leave the operator with the potential to easily mess up.

    Operating on the wrong leg or arm, is inexcusable (processes can make this essentially impossible). Having the sharp scalpel with freedom of movement that lets a surgen cut something that causes a problem might well be a situation that has to exist in order to allow them to do what is needed. They probably need to be able to have dangerous sharp items to do what is needed, we can do things to make the environment safer but the process can't eliminate all risk (as far as I can imagine) in some cases.