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ZERO Defects and AQL

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  • #38159

    Pablo Quintana
    Participant

    Guys,I have a dilemma. Currently in our plant we use AQL methods to check for defects. I am proposing to use 100% inspection by operators and eventually reduce or eliminate AQL as the main defects detection method.Production is concerned about the time the operator will spend inspecting parts.What would be the “modern” approach from Six Sigma/Lean point of view to detect errors?

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    #113857

    K.Subbiah
    Participant

    Pablo:
    Lean and Six Sigma emphasize on 100% quality made at the source through both philosophy and measures used to assess performance. Technically,  100% inspection by operators after the product is made is considered waste Therefore, understand the issues and opportunities for mistakes at the process (using FMEA and blue prints from customers) and put pokayokes in place in the processes so that you stop the machine when the first defective piece occurs. Also, track your customer returns, return issues, warranties, field issues, etc. These plus internal scrap, rework, inspection, and sort issues will give you enough to work on. Good Luck.    

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    #113919

    Pablo Quintana
    Participant

    Thanks,We have some automated processes, but mainly operators with hand made processes on an assembly line. Inspection will be to vissually check if previous operation is OK and after he makes the operation, wether or not is OK. No instruments are used to check quality of products by operators.What I’m facing now is that operators do not feel responsible for quality, because they are expecting the quality inspectors will catch defects during in-process audits or at AQL audits at the end of the line. I am trying to empower the operators to know good from bad.We have made FMEAs to limit what quality inspectors will check during process audits.I will appreciate your comments.

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    #113927

    Peppe
    Participant

    First thing to do is to evaluate the cost of poor quality against the cost of inspection and its impact on your customer and do a balance.
    Anyway, a part of economics point of view, I think you are moving in the right way, because quality isn’t to check after errors are made, but prevent it by people that do it. So, when an high quantity of work is from manual operations, empowering the people is the right way.  FMEA is good start point and you can apply 100% of visual inspection for a limited period of time, so that you can have a very clear pictures of your issues and then move to the process and tools, with empowered people, to set up the improvement activities. But, my last suggestion, is to try to set up a process management activities, so that you aren’t so tied up to the operators.
    Rgs, Peppe

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    #113929

    Pablo Quintana
    Participant

    Thanks Peppe,
    Yes, we will setup process management activities to avoid depending on operators.My idea is to identify the main defects, locate source and eliminate them, but with people empowered.

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    #113932

    Peppe
    Participant

    Pablo, you are absolutely correct. Empowering people is the right way. You are enough skilled to know that from  operators come many good improvement suggestion. Another good tool used in our facilities, when human work is main contributor, is the issues startification, so that each people at each step of manufacturing,  is focused on the right things (it comes from FMEA analysis).    
    Rgs, Peppe

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    #114395

    RR
    Member

    Pablo,
    I am also into a project very similar to you. But I have one question. How big is the human aspect in your process? The reason why I ask this is, our process is mostly manual (only very few automations) and the population handling this process is abt 1000 people. I wonder if at all it is possible to bring in zero defect by empowering people and without constant inspection.
    Rgds,
    RR
     

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    #114398

    Anonymous
    Guest

    Pablo,
    Further to some of the excellent answers you’ve received, you should consider the following:
    1. One of the principles behind six sigma is that you can use a ‘natural process capability’ to produce very low numbers of defects – approximately zero defects.
    2. One of the principles behind Lean (Toyota Production System) is that sometimes it is not possible to use a ‘natural process capability’ to achieve a world-class competitive product. Also, sometimes ‘defective’ product is hidden within the good. Therefore, it is necessary to perform 100% inspection, but the question is how to do it without creating ewxcessive waste (Muda.) The solution can be found in autonomous inspection or Jidoka. Poke yoka is an example of Jidoka.
    Jidoka uses inspection jigs or process self-assurance to check each product one-by-one, which is the reason behind single-flow) ikko nagashi.
    PS. The answer describing quality as a ‘matching process’ is excellent – each component has to be matched to a jig or standard at each step the process – step-by-step. This is what is referred to as Kaizen – making each step right.
    Regards,
    Andy

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    #114408

    Ben Royal
    Participant

    You might want to spend some time reading what Shigeo Shingo has to say about mistake proofing and Zero Quality Control. He has a couple of books out on this subject that will be very helpful.
    Good luck. 

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    #114411

    Anonymous
    Guest

    Ben,
    According to Shingo-san sometimes it’s important to know WHY instead of just HOW.
    By the way Shingo-san invented poka yoke.
    Good luck to you to.
    Andy

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    #114412

    MudaSensei
    Participant

    Yes, that was his real power……..asking the right questions….and not just answering them.
    Makes one think !

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    #114572

    Mansho
    Participant

    Pablo,
    Shouldn’t you be focussing your attention on improving your processes to ensure minimal defects are produced? You cannot rely on humans to ‘inspect qualtiy’, haven’t you heard the saying “100% inspection is only 80% effective”, i.e. 1 in 5 defects will pass through your proposed inspection process. Use your BB’s to analyse your defects/concerns and implement robust process solutions. Training & Inspection are NOT forms of Control……….
     

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    #114577

    Pablo Quintana
    Participant

    RR,We have around 600 people during manual processes on our plant, and very few operating machines.I read an article on Quality Progress this weekend where they talk about DEFENSE and OFFENSE. Operators can be Guerrillas using DEFENSE techniques like detecting errors and doing containment actions, but a more specialized team has to be in the OFFENSE side, like Carpet Bombers, Sharpshooters and Lone Rangers (BBs, GBs, Lean Experts, Process Experts). These people will attack source problems, but mean while Guerrillas will manage the day-to-day problems. Remember big, complex problems take somewhile to defeat.

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    #114578

    Pablo Quintana
    Participant

    I would say, doing both things: improving (specialized groups and operators) and containing (operators).

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    #114659

    Jonathon Andell
    Participant

    You could consider using AOQL instead of AQL. The difference is this: AQL is based on the likelihood of rejecting a good lot, while AOQL is based on the likelihood of shipping a bad lot. Thus, AQL protects the supplier, while AOQL protects the customer. In the customer-focused world of Six sigma, AOQL is vastly better than AQL.There also exist sampling schemes where you increase the lot sample size when defects cross a threshold, and return to smaller sample sizes when the defect rates come down.All of this is compatible with process improvement initiatives like Six Sigma.

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