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Special characteristics

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  • #27068

    Gunnar karlsson
    Participant

    Can any one give me information about special characteristics, how do you define them.

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    #65878

    Joe Perito
    Participant

    “Special Characteristics” is the term coined by the automotive industry. It refers to characteristics that can no be measured as the process is running, thus, requiring continuous process monitoring. An example is welding. You can not “measure” a weld quality real time. Therefore, you have to continuously monitor the electrode quality, the current, the voltage, the speed , etc. One of the keys to the deffinition is that you can only evaluate the quality of the parameter “after” the product is built. Such methods may include distructive testing or eddy current of the weld after the fact. Paint lines, nitride dip and gas systems, plating systems and circuit boards built by automation and solder wave dipping can fall into this catogory also.

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    #65879

    Joe Perito
    Participant

    A little more info: Since the product can not be tested as it is built and continuous process monitoring is required, it is obvious that the quality of these products could suffer if the processes making them are not monitored closely. For this reason, the automotive industry requires you to identify such process in your FMEA’s, control plans, design drawings, and on-line quality check sheets by a special symbol. Ford requires the upside down triangle or “inverted delta”. GM will allow different symbols as long as your documentation show the symbol and has a legend defining what it is. The symbol also has to be defined in your company procedures and documented in your traning records informing employees what the symbol means. Chrysler uses the pentastar.

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