The screw-fastening assembly process is one of the most widely used fastening methods in current industrial assembly. However, very little research has been conducted in this area in terms of the effect of the screw-fastening process on the assembly accuracy. In this thesis, we have studied the effect of various factors on assembly accuracy during the screw-fastening process by using design of experiment and performing a repeatability experiment with a multi-dimensional high-resolution optical position monitoring system in a controlled environment. Based on our studied, the displacement of the work piece due to the screwing process is in the order of a few um to a few tens of um in the lateral direction and a few urad to a few tens of urad in the rotational direction. Furthermore, the s...[ Read more ]

The screw-fastening assembly process is one of the most widely used fastening methods in current industrial assembly. However, very little research has been conducted in this area in terms of the effect of the screw-fastening process on the assembly accuracy. In this thesis, we have studied the effect of various factors on assembly accuracy during the screw-fastening process by using design of experiment and performing a repeatability experiment with a multi-dimensional high-resolution optical position monitoring system in a controlled environment. Based on our studied, the displacement of the work piece due to the screwing process is in the order of a few um to a few tens of um in the lateral direction and a few urad to a few tens of urad in the rotational direction. Furthermore, the screwing process is quite repeatable. Among the investigated factors, number of screws, datum pins, washer, and holding force appear to be important affecting factors for the assembly accuracy of the screw-fastening process.

In order to improve the assembly accuracy of the screw-fastening process, in general one can use additional screws, keep datum pins or other sideway displacement constraint retained during the screwing process, add washers underneath screws and put holding force on the work piece. In addition, as we found that the screwing process is quite repeatable, it is also possible to pre-compensate the accuracy of the screwing process by calibrating the screwing process beforehand.

Key Word: Screw-fastening process, Assembly accuracy