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Make a decision for "stop production line"

Discussion in 'Manufacturing and Related Processes' started by Pham Van Khanh, Dec 23, 2016.

  1. Pham Van Khanh

    Pham Van Khanh New Member

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    Hi all !
    Can you give me an advice for this situation ?
    When I dectect a problem or defect (maybe, defect rate = 0.5%, 1%, 5% or more.... ), what can I base on to stop production line ?
    Have any standard for this ?
     
  2. Vintage Goose

    Vintage Goose Active Member

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    Hi Pham, Standards do not usually define decision making such as this. The decision to stop production is taken on the basis of risk; risk to users, risk to operators or risk to the company. This is something that ideally needs to be defined in advance during development with the full agreement of senior management. That way you are not solely responsible for stopping production.
     
    Pham Van Khanh likes this.
  3. Jennifer Kirley

    Jennifer Kirley Moderator Staff Member

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    The decision to stop production is based on relative cost. For continuous streams of product that gets inspected, Management can determine an acceptable quality level (AQL) and decide to sample on the basis of "protecting the customer." Statistical determination of sample size can help reduce the risk of missing flaws; deciding on whether to accept if one part out of the sample fails or zero parts fail is based on risk also. The risk of failure in production of writing pencils would be less than that of automotive brake fittings; the sampling plans for each would be based on the differences in risk.
     
  4. Bev D

    Bev D Moderator Staff Member

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    There are rules of thumb that can be invoked.
    The first is from teh Toyota Production System where the line is stopped (physically by pulling a cord that stops the assembly line in the case of automotive assembly) anytime a defect is detected on the line. Now the practical rule of thumb on this is that if it is an isolated single incident that can be corrected without stopping the line Then the line continues, but as soon as this is not possible the line is stopped. Having only enough material at the line to produce the number of products on the line facilitates this. So if a bolt must be replaced, there aren't enough bolts at the line to do it without stopping and asking for more bolts. This leads to an immediate investigation into why the bolt must be replaced. The sooner we address defects the more likely we are to get to the cause. If the cause is complex then the investigators can develop a containment plan to get the line running again with quality parts before they get to the cause a permanent fix.

    The second rule of thumb is more traditional: as Jennifer stated it is based on risk and the need to protect the Customer. If the defect has a severe effect adn there is no known effective detection method and/or rework/repair, then stop making bad parts at least until an effective detection method and rework/repair can be implemented.
     
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