As problem of title, I have received the problem report from quality assurance department.

I would like to inform about problem report detail.

  • Problem detail
    Product ; ARTC72LATU
    Quantity ; 16
    Problem contents ;
    There have been several ARTC72LATU with the fan barrel becoming lose on the motor shaft.
  • Analysis result
    1) Confirmation of process inspection history at factory
    There is not repair history at this product.(Appendix 1)

    2) Confirmation of manufacture process.
    *Coat SCREW ROKK VARUISH RED on near the hexagon socket.
    *Insert SIROCCO FAN into motor shaft(fit)

    *Tighten a screw at D-cut by manual torque wrench. (prescribed torque is 4.0 to 22.6Nm)
    * Mounting state is confirmed by cyclic check.
    * Confirmation that there is wobble or not. (minimum torque that wobble occurs is approximately 0.5 to 1 Nm)
    * As to noise check process, noise, vibration and electric current of fan are confirmed by all fan speed setting such as S-Low, Low, Med and High.
    * As to sampling inspection, confirm operation by using one unit in lot. At same time, noise and allophone are also confirmed.

    3) Confirmation of manufacture product
    * Checked 10 manufacture product, then, the result was 10~15Nm.

    4) Replicate test
    * Tighten a screw by torque is 4 Nm(minimum value of prescribed). Then, operation/stop were carried out at 500 times.
    As the result, there is no problem such as bolt loosening and noise.

    * Tighten a screw by torque is 3 to 1 Nm(minimum value of prescribed). Then, operation/stop were carried out at 500 times.
    As the result, there is no problem such as bolt loosening and noise.

    * FGL guess that;
    if toque is less than 1Nm, wobble will occur. As the result, noise will occur.
  • Speculation of this result’s cause
    * FGL guess that there had been product that the screw was tightened weakly was happened.
    After installed, screw loosening occurred by operation repeatedly.
    Then, the fan and the casing touched. As the result noise occurred.
    * Toque management could not been carried out. because, factory worker had used manual range at tighten a screw process.
    As to Replicate test at this time, FGL could not find the problem.
    But, there is possibility that there had been product that the screw was tightened weakly.
  • Measure
    *Changed the manufacture process that worker becomes to use torque wrench in screw clamp process.
    Torque setting is 20Nm.(From 18th July 2014)(Appendix 3)
    *Additional tightening torque for assembly specification.(from 2nd Sep 2014)(Appendix 2)
  • Measure to product
    Already installed product; measures by each location if problem is occur.
    Stock product; No measures. FGL think this problem will not happen often.
    Manufacture product ; already measured.