Three dimensional (3D) CAD (computer-aided-design) models have enabled major productivity gains in product design and engineering. Prior to the advent of economical desktop computers skilled draftsmen spent hours laboring with graphite lead pencils on velum and Mylar to achieve engineering quality documentation for fabrication and production manufacturing. The process required tedious checking to eliminate errors wherein modification required erasures and redrawing over and over on the same sheet. Large projects had many drawing documents linked to one another that required procedural revisions and archiving.

Two dimensional (2D) CAD (computer-aided-design) was a great step forward in moving from the drafting table to the desktop computer. The graphical display capabilities of the desktop computer enabled a user to graphically draft using mouse, keyboard strokes, text line commands, and tablet with stylus. Each CAD system had its own (UI) User Interface. While manual drafting may have actually been faster in the early years, two dimensional (2D) CAD (computer-aided-design) technologies allowed endless changes to be made with sharp clean printed copies printed without limitation. It was easy to export the CAD drawings in PDF format for viewing and printing on any non-licensed computer.

CAD data exchange remains a challenge for designers and engineers during the product development stage and in the data turnover to manufacturing. Among the many 3D CAD systems there is limited data transfer capabilities that retain native feature functionalities. Accordingly CAD data is routinely transferred between CAD platforms using IGES (Initial Graphics Exchange Specification) and STEP (Standard for the Exchange of Product model data) formats. While these exchange tools provide for generally good data transfer they do not transfer feature creation data and are thus inflexible for modification. While CAD publishers recognize this as a problem and have tried to address it; to date there has been poor result in translating anything but primitive geometric forms which are comprised of planar, cylindrical, revolved, and spherical surfaces. Parts that require splined curves and surfaces remain problematic to transfer from one CAD platform to another. The reason for this is that primitives are defined mathematical different from those of complex surfaces. While primitive geometries consisting of planar, cylindrical, ruled, spherical, and revolved surfaces and can be defined by unlimited discrete mathematical coordinates, those that are defined using spline surfaces require polynomial equations with interpolation to transition between defined curvature patches within the surface curvature network. The interpolation aspect of surface data translation is the basis of the popular commentary on IGES translation which is that IGES is an acronym for "I guess." http://www.cadmodels.biz/import_3d_cad_data_exchange_and_data_repair.html