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Method for determining positioning reference of type V block

  Determination of positioning criteria for type V blocks

  The V block is a special positioning element. Although it is a separate positioning element, but its structural elements base location is not a single, two plane positioning, positioning speaking this form from some kind of meaning can be seen as the two plane positioning. Therefore, the determination of its positioning benchmark can not be as simple as analyzing a single positioning base plane.

  Most of the positioning reference positioning element are positioned to base itself or is formed from the point, line, plane, such as a single center and the center line of the shaft hole, etc.. According to this principle, the author believes that the V type block location datum should be two, one is the intersecting line of two plane, the other is a center of symmetry plane formed by two planes perpendicular to the direction of the intersection as the positioning reference; reference positioning center of symmetry plane as the horizontal direction.

  According to the traditional theory (Theory) datum of V type block should be test spindle center height, which is to check the center line of spindle in V type block placement, this position is actually the center line in the V block is not exact, because it will change the size of the mandrel diameter error test therefore, the position error in the alignment error will often introduce the center line. If the V type block positioning plane and cylindrical workpiece contact bus (on the bus) as the base location, because there are two common positioning positioning the base, the workpiece to achieve the correct positioning, so that the bus should be to make reference? It seems this method is not the exact problem, this view not only makes the formula the process of positioning error is trivial and complicated, and the formula of ambiguous.

  Since the V block is a combined positioning of two planes, it is impossible to analyze the positioning reference of the positioning element of the single surface by means of the positioning reference method. For example, with a two hole workpiece positioning is used for locating elements is a two pin, two pin center line is often used as a positioning vertical connecting line direction position requirement is not a benchmark to pin center line or cylindrical surface of the locating datum.