Geometric product specification

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The geometrical product specification (GPS) is a set of rules of the ISO , which contains the description, tolerance and testing of technical products.

With the development of standards for geometrical product specification ( GPS , English Geometrical Product Specification ) the following technical committees are involved, among others:

ISO / TC 213 “Dimensional and geometrical product specifications and verification” in cooperation with CEN / TC 290 “Geometrical product specifications and verification”.

In the age of globalization, internationally understandable specifications are essential. For this reason, standardized symbols are used in the product description and descriptive texts are avoided whenever possible.

According to DIN 32869, workpieces must be in their geometry description

  • functional (probably the most important requirement),
  • suitable for production (e.g. inexpensive production) and
  • suitable for inspection (refers to quality management)

be fixed.

This can be done in the form of paper drawings or with the help of a CAD data model. This so-called specification model must

  • complete (all essential properties must be specified) and
  • clear (no different interpretations may be possible)

be.

A drawing of the above Conditions not met, cannot be used as a basis for production and quality assurance. A complete and unambiguous description of a workpiece is e.g. B. not possible without shape and position tolerances ! The description of the workpiece must contain appropriately tolerated dimensions with functionally reliable tolerated geometrical deviations. Often, the tolerances are chosen too precisely with regard to the function, which leads to unnecessary additional costs in production and quality assurance.

In international standards, the manufacturing tolerances are divided into three areas, namely into

  • the dimensional tolerance of dimensions and angles,
  • Shape, position, location and direction tolerances and
  • the surface properties or roughness tolerances.

When applying these tolerances are u. a. the following tolerance principles must be observed:

  • the envelope or independence principle,
  • the minimum condition,
  • the maximum material condition,
  • the minimum material condition,
  • the reciprocity condition,
  • the tolerance rule for general tolerances as well
  • the arithmetic or the statistical tolerance chain simulation.

The development of new standards and the integration of existing standards is regulated and organized by the GPS matrix . It is based on ISO / TR 14638 "Geometrical Product Specifications (GPS) - Masterplan".