What is a positionner or a CMM fixture?
As its name suggests, a positionner is an element of fixation enabling to position a part by aligning it by its RPS on a CMM machine. Contrary to a checking fixture, which also positions the part in the same way, a positioner does not have any type of control element giving information about the part, and enable the CMM probe to access easily to the areas to measure. This picture displays a positionner fastening a puffed plastic tank in vehicle coordinates for its measurement by CMM machine. As it also represents the part fixation points, it can also be used as a checking fixture for these areas.
