Dimensioning is a method of accurately communicating size information about objects and structures so they can be produced. Dimensioning of mechanical devices follow standards established by ANSI. These standards guide you in the proper use and placement of dimensional information on an engineering drawing. Many parts need to be dimensioned using toleranced values. Tolerances allow a dimensional value to vary within limits set by the designer. Toleranced dimensions are useful in the accurate manufacture of assembled parts. Geometric dimensioning and tolerancing (GDT) is essential to the modern manufacturing environment. The first rule of GDT is that size control of a feature (as is given in a dimension) inherently includes controls of form. The goal of GDT is to carefully evaluate the functionality of a part and its features and only control the geometry of those features necessary for the proper functioning of the part. Also related to this goal is to remember that usually involves the loosening, not tightening, of tolerances because its robust specificity allows for trade-offs between size and form. Together, these qualities of GDT, when combined with statistical process control, should help minimize manufacturing costs. This process leads to controlling the fewest number of features, at the largest allowable tolerance, and is confirmed through checking the fewest number of parts; all of this while still keeping quality within a quantifiable goal. |
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