Poka-Yoke Dhon G. Dungca

What is Poka-Yoke? Poka (Poh-Kah) Yoke (Yoh-Kay) 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 Causes Chemical 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 Causes Delay 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 Misunderstanding 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 Made by Amateurs 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 Inadvertent 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 Lack of Standards 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 Intentional Errors Equipment runs differently than expected Intentional Errors We make mistakes deliberately

How to deal with errors Errors happen Errors can be eliminated “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

Approaching ZD (zero defects) 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! Make it to withstand any use! 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 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 Omitted processes Fixed values Weight, dimension, shape Omitted processes Process sequence method Fixed values Using counter