1. Mistake Proofing
Control
Kaizen Facilitation

2. Objectives
Review top causes of errors and the importance of mistake-proofing
Learn 3 functions of a mistake-proofing measure:
Shutout
Control
Warn
Recall the steps to mistake-proofing
Explore examples

3. Approaches Inspection / Judgment
Discovers defects after they have happened
A person or piece of equipment inspects/compares product or service with a standard, discovers items don’t conform and rejects them
Focus on alerting defect producing process about the problem
Statistical Process Control (SPC) – Process Behavior Charts
Self-check of each output
Successive checks of each output
At The Source [Focus of Mistake-Proofing Measure]
Catches errors before they cause defects
Uses devices (methods) to shutout (or shut-down), control, or warn of an improper process

4. Inspection/ Judgment Method Exercise
Read the sentence below and count the number of times the letter f appears. When you are asked to stop, note the number of f’s you have counted.
Finished files are the result of much effort
of many people effectively filing the
materials of many other persons.
Number: ____

5. Top 10 Causes of Errors
Processing omissions: leaving out one or more process steps
Processing errors: process operation not performed according to the standard
Error in setting up: using wrong tooling or incorrect setting/ adjustment
Missing parts: not all parts are included in assembly/ process
Improper part/ item: wrong part installed in assembly

6. Top 10 Causes of Errors (continued …)
Processing wrong work piece: wrong part machined/ processed
Operations errors: incorrect revision or specification sheet
Errors in equipment, maintenance or repair: Defects caused by incorrect repairs or component replacement
Error in preparation of inspection equipment, fixtures or tools: Damaged inspection tooling; poorly designed fixtures or wrong tools; mis-measurement

7. Errors are the actions that cause defects
Errors and Defects
Defects
Errors
Errors are the actions that cause defects

8. When to Focus on Mistake-proofing
When a process step has been identified where human error can cause mistakes or defects to occur, especially in processes that rely on the worker’s attention, skill or experience
In a service process, where the customer can make an error which affects the output
At a hand-off step in a process, when output or (for service processes) the customer is transferred to another worker
When a minor error early in the process causes major problems later in the process
When the consequences of an error are expensive or dangerous

9. Detection or Prevention
People make errors & errors can lead to mistakes
However…
Mistakes can be eliminated through the use of mistake proofing devices (poka-yoke) that are used to either detect or prevent defects from occurring in the first place

10. Functions Basic mistake proofing functions to use against defects:
Shutout / ’shutdowns’ machine, process or operation
Control a process or operation
Warn that a defect has occurred (or is about to…)

11. Determine Process Condition
Following process produces defects
Change process, defects go away
Generally, easiest to change
Incorrect Process
Process hard to follow consistently
Process problem, not people problem
Process Not Followed

12. Definition
A ‘poka-yoke’ or mistake proofing device eliminates defects by preventing errors.
What does it mean?
poka – error (foolish action); yoke – to avoid
Replaces earlier version baka yoke (fool proofing) – a more negative connotation

13. Poka-yoke Reduces Window of Waste
Potential Error – No power for laptop back at the Hotel
1) Drive to Hotel
2) Check-In Hotel
3) Plug-in Computer
T i m e
Mistakes happening within several ‘windows’
Consider several “Interventions” (measures)
1) Attach Car Keys on Power cord
2) Hotel Key(s) in Wallet / on Lanyard or Belt Loop
3) Extra power cord in Computer Bag (redundancy)
“It is good to do it right the first time: it is even better to make it impossible to do it wrong the first time.”

14. Mistake-proofing Steps
Step 1: Identify and Describe the defect/ red flag condition
Step 2: Determine root cause (where the defect is discovered or where it is made)
Step 3: Detail the sequence of events in the standard procedure
Step 4: Review the steps that differ from the standard (deviations)
(identify contributing conditions or potential failure modes)
Step 5: Identify the mistake-proof device type required (S,C,W)
Step 6: Create device(s) and test for effectiveness (incorporate into Standard Work practices)

15. Examples
Microwave Oven
(Shutout)
Garage door sensor
(Shutout)

16. Examples Fuel Gage w/ indication light Automatic MPG calculation
(Warn)
Automatic MPG calculation
(Control)

17. Examples
Gas Cap Eliminated
Tethered Gas Cap
(Control)

18. RR Crossing Eliminated
Examples
RR Crossing Eliminated
RR Crossing (Warn)

19. No skateboarding allowed
Examples
No skateboarding allowed
(Warn)
Decorative Metal tabs
(Shutout)

20. Examples
Uniform
Signage On
Terminal

21. Examples
Standardized Vessel Labor
“Start-up” / Line-up Routine

22. Guidelines 1. Try not to spend. 2. Simpler is better.
3. Don’t make them optional.
4. Don’t confuse gages (process checks / verification) with mistake proofing.
5. Eliminate decision making.(Done only one way!)

23. “Red Flag” Conditions Adjustments Hand processing
Unclear or no instructions
Rapid repetition
Undefined process
High volume demand or deadline pressures
Many units/mixed units
Environmental conditions
Multiple steps
Infrequent production
Ineffective or lack of standards
Multiple handoffs

24. Review
Use an inspection approach for preventing defects (mistake proofing at the source) by applying prevention methods at the point in the process where the defects originate
Always validate 100% (process check / step verification)
Provide for immediate feed-back for corrective action when errors or defects are detected
Because humans are not infallible, use mistake-proofing measures to prevent mistake causing errors or at least to warn that a defect or error has occurred
Strive for Shut-out