Post on 17-Dec-2015
Poka-Yoke
Dhon G. Dungca
What is Poka-Yoke?
Poka (Poh-Kah) Inadvertent errors
Yoke (Yoh-Kay) To avoid
Technique for avoiding simple human errors at work
“fool-proofing” “fail-safe” “mistake-proofing the process”
Shigeo Shingo
Developed the idea into a formidable tool for achieving zero defects and eventually eliminating quality inspections.
Poka-Yoke EVERYWHERE!
Elevator alarms 110V/220V plugs Low battery indicator Low fuel indicator Alarm clock
3.5 Diskette
Cannot be inserted unless diskette is oriented correctly. This is as far as disk can be inserted upside-down. The beveled corner of the diskette pushes a stop in the disk drive out of the way allowing the diskette to be inserted. This feature, along with the fact that the diskette is not square, prohibit incorrect orientation.
File Cabinets
Can fall over if too many drawers are pulled out. For some file cabinets, opening one drawer locks all the rest, reducing the chance of the file cabinet tipping.
Bathroom Sinks
Even bathroom sinks have a mistake-proofing device. It is the little hole near the top of the sink that helps prevent overflows.
Key Holder
In China, where electric power has been scarce, hotel rooms are equipped with a room key holder which turns off the power when the key is removed. This ensures no electricity flow to the room while it is vacant.
ATM Machines
New generation ATMs perform transactions without the card leaving your hand because of the beeping sound once your card comes out of the machine
Elevators
Many elevators are equipped with an electric eye to prevent doors from shutting on people. They also are equipped with sensors and alarms to prevent operation when overloaded.
Why Poka-Yoke?
FACT! Workers finish their shift & don’t
remember what they have done Even highly skilled workers get tired
and start committing mistakes Workers get distracted and forget on
a valve or switch
TIPCO Experience
Incidental Details Root CausesChemical valve at kneading machine left open
Wrong delivery to customer
Unaccounted requisition causes distorted inventory stock
Overflow of whitewater storage tank
Human Error
Wrong label generated and pasted on roll
Misplaced actual stock requisition form
Unable to monitor level
TIPCO Experience
Incidental Details Root CausesDelay at truck scale
Fresh water tank emptied
Truck ran out of fuel
Forgot to put the control value to auto after cleaning the strains
Fact!
To Err is Human!
Kinds of Human Errors
Forgetfulness We forget things when we are not
concentrating
Misunderstanding We make mistakes when we jump to
conclusion before we are familiar with the situation
Kinds of Human Errors
Identification We misjudge a situation because we
view it too quickly or are too far away to see it clearly.
Made by Amateurs We make mistakes through lack of
experience
Kinds of Human Errors
Willful Errors We decide that we can ignore rules
under certain circumstances
Inadvertent Errors We are absentminded and we make
mistakes without knowing how they happened
Kinds of Human Errors
Due to Slowness We make mistakes when our actions
are slowed by delays in judgement
Lack of Standards Errors occur when there are no
suitable instructions or work standards
Kinds of Human Errors
Surprise Errors Equipment runs differently than
expected
Intentional Errors We make mistakes deliberately
How to deal with errors
Errors happen “Errors are inevitable. The mark of
character is not refusing to recognize them, but acknowledging them and taking responsibility.”
Errors can be eliminated People make fewer mistakes if they are
supported by proper training and by a production system based on the principle that errors can always be prevented.
5 Best Poka Yoke
Guide pins of different sizes Error detection and alarms Limit switches Counters Checklists
Poka Yoke Devices
Vibration sensors Metal sensors Timers Computer-activated devices
Poka Yoke…
Approaching ZD (zero defects)
Sampling vs 100% Inspection
Sampling inspection “we maintain our quality at 99%”
100% Inspection “we won’t tolerate a single defect.”
3 Strategies for ZD
Don’t make it! The more products you make, the greater
opportunity for defects to sit in inventory. Make it to withstand any use!
Build safeguards into the production process to ensure that the product is robust from the user’s viewpoint
Once you’ve made it, use it right away Go for continuous flow production
Inspection Techniques
Judgment Inspection Separates defective products from
good ones after processing Informative Inspection
Uses data feedback to control the process and reduce the defect rate.
Source Inspection Determines before the fact whether the
conditions necessary for high quality production exist.
Prediction vs Detection
Prediction System acts before a defect occurs
Detection System does not allow continuation
Basic Poka Yoke Functions
Shutdown Normal operations are stopped when
defect is detected or predicted Control
Prevents defective items from passing on the next process
Warning System signals when an abnormality is
about to occur or that a single defect has already occured
Basic Poka Yoke Functions
Shutdown Normal operations are stopped when
defect is detected or predicted Control
Prevents defective items from passing on the next process
Warning System signals when an abnormality is
about to occur or that a single defect has already occured
Where “Mistake-Proofing” works well
Manual operations were worker vigilance is needed
Where mispositioning can occur Where adjustment is required Where SPC is difficult to apply Where special causes can reoccur Where external failure costs
dramatically exceed internal failure
Detection Method
By characteristics Weight, dimension, shape
Omitted processes Process sequence method
Fixed values Using counter