A fixture failure control chart for variation caused by assembly fixtures

In the auto body assembly process, fixtures are used to position parts during assembly and inspection. If there is variation in the positioning process, this will propagate to the final assembly. There are also other sources of variation in the final assembly, such as variation in parts due to previous manufacturing steps. To facilitate the separation of the different sources of variation, and thereby also improve fault diagnosis, a fixture failure subspace control chart is proposed. This control chart is based on a multivariate T 2-chart, but only variations in the fixture failure subspace are considered. The method is applied to two industrial case studies with satisfying results