ISO recommendations for micro and macro geometry tolerancing of mechanical parts and their significance.

Dimensional, geometric or surface finish specifications are symbolic tools indicated on part definition drawings or on a specified 3D model (3D specification annotation) to transcribe the functions expected on or in the system.

An industrial part is defined by design offices to perform a specific function at minimum cost.

Based on functional specifications, the designer selects technical solutions and defines the overall drawing of a system, followed by the definition drawings of its components.

These definition drawings are communication vectors that enable the design office to describe its expectations to other departments (manufacturing, measurement, purchasing...).

Based on a definition drawing, the method-manufacturing departments can determine the production process(es) best suited to the production of the requested part, with the support of the quality control-measurement department, which itself defines the optimal measurement or control processes to guarantee product conformity with all the requirements mentioned on the definition drawing.

It is also thanks to this definition drawing that the purchasing department can consult suppliers.

The definition drawing contains various items of information:

• nominal part geometry ;

• nominal dimensions ;

• the subject ;

• requirements described in terms of dimensional, geometric or surface finish specifications.

This set of elements defines what is expected of the parts, and is inevitably associated with a cost.

The aim of this article is to present dimensional, geometric and surface finish specifications, and the links between the various players in the business. In a nutshell, the technical players seek to realize functions through product specifications, while minimizing their production costs (manufacturing, control, logistics, etc.).