2.1. Definition of straightness error end for tolerance of straightness
At German VDI/VDE 2617/Part 3 (1989) the definition for straightness error is: “When a reference point on the moveable part of machine moves over its travel range, a line of movement is described. The deviation of this line to a straight line is the straightness error.”
According to BRYAN (1979) “slide straightness error is the non-linear movement that an indicator sees when it is either stationary and reading against a perfect straightedge supported on a moving slide or moved by the slide along a perfect straightedge which is stationary”.
The tolerances are defined by some standards such as the Brazilian ABNT. According to ABNT geometrical tolerances are limits to the dimensional and geometrical deviation of the part and have to be specified in the project. Straightness tolerance controls the deviation of the shape of the feature from its true shape. The tolerance zone, according to NBR6409, is defined by:
- The straightness of the axis of a solid of revolution, as shown in Fig. (1). In this case the tolerance zone is a cylinder whose diameter is the tolerance value.