Poka-yoke is a quality assurance technique that aims to eliminate product defects by preventing human errors during production. It works by incorporating mechanisms that detect errors and provide warnings or corrections. Examples of poka-yoke include sensors that check weight limits in elevators and vision sensors that inspect parts on production lines. There are three main types of poka-yoke: contact methods that check physical attributes, fixed value methods that detect incorrect counts, and motion step methods that verify process steps. Implementing simple, inexpensive poka-yoke devices can significantly reduce defects and costs for companies.

1. SUBMITTED BY:
AKSHITA PILLAI
MCAIIIrd SEM.

2. CONTENTS
• History
• What is Poka Yoke
• Why is it important?
• Example
• Key Principle
• Types of Poka Yoke
• Poka Yoke System Design
• Fail Safe Device/Machine
• Sensor for detecting defects
• Reason of using vision sensor and its working
• Cognex-Checker Vision Sensor
• Vision Sensor Inspections
• Vision Sensor example in motion
• Conclusion
• References

3. POKA YOKE (yokeru)
“Mistake” “Avoid”

4. HISTORY
 This term Poka-Yoke was adopted by Dr.Shigeo
Shingo as part of the Toyota Production System
in 1960.
 It was originally described as “baka-yoke”,but this
name mean “Fool Proofing", so the name was
changed to the Poka-Yoke.

5. WHAT IS POKA-YOKE?
 Poka-Yoke is a Quality Assurance Technique, its
purpose is to eliminate the product defects by
preventing, correcting or drawing attention to human
errors as they occur.
 Its objective is to achieve “Zero Defects”.

6. WHY IS IT IMPORTANT ?
 Poka Yoke refers to the technique which can drive the
defects out of the products and improve quality and
reliability.
 By eliminating the defects at the source, the cost of
mistakes within a company is reduced.

7. EXAMPLE OF AN ELEVATOR
 A traditional lift set up by an engineer in a building
has maximum weight capacity is 200 kg.
Person 1=60 kg
Person 2=90kg
Person 3=50 kg
LIFT
CAPACITY=TOTAL
WEIGHT

8. CONTINUED…
 If more people enter the lift then weight will increase,
which increases the possibility of break down of
lift’s wire because there is no warning mechanism on
excess weight.

9. CONTINUED…
 Latest lifts are very advanced, because when it is
over weight the alarm will start & indicate light , until
weight is not reduced, this is done through Poka yoke.
 And lift will move without any fault.
Here
people want to use lift but they can’t use it, why
?
Because lift can’t run on overload. This is good
for our safety, so here no any defect comes out .
This is also called zero defect.

10. KEY PRINCIPLE
Error is inevitable, but it should be eliminated.
Before Poka Yoke After Poka Yoke

11. TYPES OF POKA YOKE
Dr.Shingo recognized 3 types of Poka-yoke for
detecting and preventing errors:
 The Contact Method
 The fixed value (or constant number)
 The motion step (or sequence method)

12. THE CONTACT METHOD
This method identifies product defects by testing the
product’s shape,size,color or other physical attributes.
Example:

13. THE FIXED VALUE METHOD
This method alerts the operator if a certain number of
movements are not made.
Example: Control or shut out Warning & Attention

14. THE MOTION STEP METHOD
This method determines whether the prescribed steps
of the process have been followed.
Example: Control or shut out Warning & Attention

16. INEXPENSIVE
SIMPLE FAIL-SAFE MACHINE
FOR
QUALITY CONTROL
SENSOR

17. FAIL-SAFE DEVICE
 Principle of Fail safe Device
It is designed in a way, so that when a failure does
occur, the device will tend to fail in a predictable
manner to a “safe state”.
Fail safe device is distinguished from Fail Secure
device.

18. FAIL SAFE DEVICE IS DISTINGUISHED FROM
FAIL SECURE DEVICE.
Fail-safe means that a device will not endanger lives or
properties when it fails.
Fail-secure means that access or data will not fall into
the wrong hands in a failure.
For example, if a building catches fire, fail-safe systems
would unlock doors to ensure quick escape and allow
firefighters inside, while fail-secure would lock doors to
prevent unauthorized access to the building.

19. SENSORS FOR DETECTING DEFECTS
For detecting defects in products, the sensor which is
used is “Vision Sensors” also known as Smart
Inspection Cameras.

20. WHY VISION SENSORS?
Repetitive inspection of production lines is a labor-intensive
activity that is being replaced by vision
sensors which are not only cost-effective, but give
consistency of judgment and documented traceability
to the inspection process.

21. HOW DO THEY WORK?
 Vision sensors have huge numbers of photoelectric cells that
capture a complete image.
 After capturing the image, the vision sensor compares some,
or a number of characteristics of the image to the reference
image stored in its memory.
 It can inspect asymmetrical objects no matter how they are
rotated within a full 360o range.
 Reference image is set using software inspection tools built-into
the sensor.
 The sensor has been programmed to enable it to locate, analyse
and measure the image and then compare the results with
preset pass or fail criteria.
 The result is communicated over Ethernet ports.

22. CHECKER VISION SENSORS
 Cognex Checker vision sensors are very good at detecting
defective parts reliably on the fastest production lines.
Equally important is the vision sensor’s ability to stop the
rejection of good parts. That’s exactly what Checker does.
 Checker Vision Sensor is an industrial sensor with built-in
camera,processors,lighting,optics capable of detecting and
inspecting up to 6000 parts per min.
 Developed by Cognex.
 Easy to setup and operate.
 Not expensive.

23. VISION SENSOR INSPECTIONS
The image display simplifies setup by
enabling you to see what the sensor sees.

24. CHECKER’S UNIQUE INSPECTION SENSORS
PROVIDE THE MOST RELIABLE WAY TO
INSPECT YOUR PART
 Brightness sensors look for dark or light areas on the part.
 Width sensors measure the width of a part, component, or
feature.
 Height sensors measure the height of a part, component, or
feature.
 Diameter sensors measure the diameter of a part, component,
or feature.
 Pattern presence sensors include “robust” and “fast” modes
to verify the presence of patterns.

25. VISION SENSOR MEASUREMENT
TOOLS IN ACTION
 Checker vision sensors have photoelectric sensors
and even other vision sensors has ability to determine
dimensions of parts and deliver simple pass/fail
results.
 Example given here – verifying component thickness
after the machining of an automotive part component.

26.  An automotive part component comes down a belt, is
machined on the production line, and moves to the
inspection station.
 The part can be in any position on the belt because
Checker is always looking for the part so there is no
need for the part to be fixture precisely.
 This means that you don’t have to adjust the sensor
constantly (like you do with photoelectric sensors).
 Once the part is found, the width, height and diameter
measurement tools quickly measure the part and
produce a pass/fail result.

27. Correct
Thickness
Incorrect
Thickness
In this example, Checker is performing part
inspections that human eyes simply cannot. The
result for the user is 100% defect detection, more
quality control, and lower production costs.

28. APPLICATIONS
 Label Alignment
Objective: To verify that the labels on a bottle are aligned
with each other and both are straight.
Sensors: Presence PLUS P4 EDGE, with LCF08 lens,
HFFW12DC tubular fluorescent light, PLC used as a trigger.
 Food Packing Inspection
Objective: To inspect boxes of chocolates for missing or
damaged pieces to make sure each nest contains a candy and
that the candies are not damaged.
Sensors: Presence PLUS P4 OMNI with LEDR80x80M light
and LCF16LMP lens.

29. CONCLUSION
In many companies,poka yoke devices are created
every week or even everyday. The ‘Kaizen’ idea
implies that they don’t have to be expensive and
should be simple. Every company, office or hospital,
certain mistakes are unwanted, but where imperfect
beings work or live, should give the idea of Poka-yoke.
It might make a big difference.

30. REFERENCES
 http://www.tektron.ie/vision_sensors.htm
 http://www.cognex.com/Connect/BlogMain.aspx?id=
12365&blogid=1825
 http://en.wikipedia.org/wiki/Fail-safe
 www.hubpages.com
 http://www.thetoyotasystem.com/lean_inventions/pok
a_yoke-you-can%E2%80%99t-go-wrong.php

31. THANK YOU