|
06/28/2012 04:13 PM
|
|
|
I know the textbook definition of each, but I am having trouble wrapping my mind around the "in the gemba" difference.
It seems that they are both "smart automation" - maybe Poka Yoke is purly quality checking where as Jidoka is any other kind of smart automation (feeding, delivering, etc)?
Share some examples of what Jidoka is and what Poka Yoke is to help me understand the difference!!
|
|
|
|
|
06/29/2012 11:01 AM
|
|
|
Think of Jidoka as the principle (don't pass defects down stream, prevent defects by preventing errors, etc.), and Poka Yoke and smart automation as tools necessary to achieve the principle.
By analogy, Just in Time is the principle. Kanban is one of the tools.
|
|
|
|
|
06/29/2012 11:02 AM
|
|
|
Dave,
I'm not the dictionary expert, but my understanding is
Jidoka is where the machine knows it is broken, like a broken drill bit, or out of thread, and stops before defects are made.
PokeYoke is a blocking device that will not allow the wrong thing to happen, or pass. A key in a lock is good example, your car key won't start another car, or the 120 volt plug wont go into the 220 volt socket
Poke Yoke - prevents bad things
Jidoka - detects bad things
Would love clarification from someone who really knows....
Dan
|
|
|
|
|
06/29/2012 11:02 AM
|
|
|
Dave the easiest way to explain is:
Poka Yoke is the design or tool or both which eliminates any possibility of incorrect fitment - hence the meaning "failsafe"
Jodoka is a quality system and by definition is (a) the automatic rejection of a faulty component or workmanship or (b) the manual ability to stop a line or process.
Hope this helps
|
|
|
|
|
06/29/2012 11:02 AM
|
|
|
Just from my understanding and I'm not a linguist so all I know is what I was taught:
Poka Yoke is a thing. Jidoka is a concept.
A poka yoke is a device or setup that makes it impossible for the human interfacing with a machine or product to make a mistake/error. Examples of pok yoke's are things like a jig that won't allow you to put a part in upside down or a plug-in that won't allow you to put the plug in the socket with reverse polarity.
Jidoka refers to the overall concept of building quality in at the source through autonomation. The fundamental concept behind jidoka is that machines don't solve problems, people solve problems. So when you design equipment, you design it to shut off when a bad product is made so that people can respond and solve that problem as soon as it is made. Also built into this concept but often overlooked is the idea of autonomy.
One of Taichi Ohno's famous quotes is that he was trying to get the factory to "work for the business the same way the human body works for the person". This is to say that when your body needs more blood, you don't have to tell the heart to pump. It does so autonomically. Jidoka is the concept that you need to design processes and systems so that when errors occur, people respond immediately in support. So at midnight on a Saturday, how do your systems respond to errors? Do the errors come to light immediately and problem solving begin or does everything wait until Monday? Jidoka would drive you to ensure that abnormalities are made immediately visible at all times and it would drive you to ensure the associates who respond to that abnormality have the capability and authority to fix it.
|
|
|
|
|
06/29/2012 11:02 AM
|
|
|
Based on my understanding, Jidoka is the detection of abnormalities in an automated process, where poka yoke is the prevention of defects.
For example, Jidoka uses sensors to detect when a part is not oriented correctly. Poka yoke would design a fixture so that the part could not be oriented incorrectly. One is detection, the other is prevention.
|
|
|
|
|
06/29/2012 11:02 AM
|
|
|
Jidoka refers to an automated system, supplemented by human oversight and judgment, capable of detecting errors. A jidoka solution would detect an error, halt production, alert a human worker to corrrect the problem and restart the system. The orginal jidoka implementation involved an automated loom that could detect a broken input strand and stop the loom until the strand was repaired.
Poka yoke is error-proofing, preventing errors through effective design. The simplest example is a component that can only fit into an assembly in a unique alignment -- the design inherently prevents improper installation. Automation may remove or reduce the possibilitiy of errors, making it a special case of poke yoke.
|
|
|
|
|
06/29/2012 11:04 AM
|
|
|
I'm hoping you'll get a number of responses, most better than mine!
Here's what I think is the difference.
Jidoka - 'autonomation' or automation with a human touch. This is the theory of designing machines/processes to run without people 'tied to the machine', meaning they are able to do other things while the machine runs. The term "mistake proofing" is also used in this context.
The best example I can give is Toyoda's original loom - it automatically stopped when a thread broke, not allowing defective work to be made. I've seen similar designs in CNC machines (stop when a tool breaks).
Poka Yoke - also "mistake proofing", but these are often simple 'check' devices that people can use to verify things are correct. They are tools that do not allow you to make a mistake. These generally aren't machine design, but rather 'catch devices'.
There are thousands of everyday examples of Poka Yoke around you daily. Garbage cans with a round hole cut in the lid for aluminum cans only. Flashing lights or cross bars that come down at railroad tracks when a train is approaching. You may have a setup cart that is 'shadowboarded' so that only certain size pieces fit in specific places (gasket holders sized exactly for the specific gaskets, so smaller or larger gaskets cannot be mistakenly stocked on the board). Requiring both hands to push buttons in order for a machine to run (not allowing you to have one hand in the machine) is another example.
Hope this helps!
|
|
|
|
|
06/29/2012 01:34 PM
|
|
|
the main difference is that Poka Yoke is a technique of thinking ahead the human error, not only at production site, but in your everyday life.
Jidoka is a technique to give autonomy to prevent errors on production site. and also to automate the decision making process, with PY devices or fixtures to prevent further issues. (if a part is bigger than spec limits, the PY will detect it, signal, push it out of sequence and stop the operation for the Supervisor to come and check)
PY could applied to finished products as well. and they are in three groups:
a) a detecting instrument (detects if correct conditions are or are not available)
b) restricting tool (prevents or stops the operation)
c) signaling devices (indicates an error is occurring)
Think about your car in all three groups:
a) leaving keys on the ignition switch, is detected.
b) in newer models you can't lock the door if key are in ignition switch.
c) while leaving the vehicle with keys on the ignition switch, car beeps.
another three examples from household ideas:
a) your Iron left on, is automatically shut down after few minutes without motion.
b) you can't turn on the Microwave oven with the door open.
c) when smoke present ,your smoke detector beeps, REALLY loud.
hope this clarifies a bit! Good luck on the Lean Journey
|
|
|
|
|
07/02/2012 11:38 AM
|
|
|
Mike
Your definition of Jidoka and Poka Yoke is right on. Too many lean consultants don't include or understand the concept of freeing people up from the machines. Instead of tying a person to one machine a good process design will have that person load, unload and montor several machines as you described.
Ron Turkett
|
|
|
|
|
07/03/2012 09:39 AM
|
|
|
Great info everyone! I appreciate all the feedback. You painted a nice picture of both concepts, what they are and what they are not.
|
|
|
>
Community >
Forums
Send to a Friend
