Functional rating

Functional dimensioning is based on an in-depth and exhaustive study of the product's suitability for use, enabling us to define the dimensions of the functional elements and their relative positions, with a dimensioning that is neither insufficient nor excessive.

To work correctly, you must first carry out a functional study of the assembly under study, using appropriate methods (functional analysis...). This will help define the actual functions to be satisfied, and facilitate the creation of a list of "dimension chains" to be verified.

It should also be remembered that "functional dimensioning" is to be understood in the broadest sense, i.e. that, in addition to dimensions and tolerances, it encompasses all other specifications, provided they are functional in that they condition suitability for use (geometric tolerancing, material, mechanical and chemical characteristics, surface finish, etc.) and even those that condition saleability: reliability, appearance, safety (no sharp edges).

However, it's important not to be too purist, because if you want to remain functional, you run the risk of forgetting conditions that are implicit in the prescription method: temperature resistance, which may exclude certain plastics, corrosion resistance (steel, magnesium) or oil resistance (for clutches and gearbox synchronizers).

The aim of this article is to advance understanding of the notion of the functional in the dimensioning of technical drawings issued by design offices, especially detail drawings, known as definition drawings (of the finished product).