Curves and surfaces for CAD/CAM

Until recently, mechanical drawings did not provide a complete description of the object they were intended to represent. Surfaces requiring some degree of precision were defined by dimensions with tolerances; their geometry was based on the use of straight lines and circles; drafts and connections were determined more or less vaguely, and sometimes implicitly, and their realization was left to the initiative of highly qualified professionals: pattern-makers, foundrymen or die-fitters. Other left-hand shapes were represented by tracings of various cross-sections, and then reproduced by copying models derived from the tracings by interpolation left to the care of highly experienced operators.

In order to use numerical control to steer boring machines, lathes, milling machines, grinding machines, EDM machines or welding machines, it became essential to have a complete and precise definition of all the surfaces to be produced. This issue has given rise to a great deal of work. A list of the main works published in French or English can be found in the bibliographic references; the list of articles published in specialized journals would number several thousand references.