The models are stored internally in a CAD or CAM system making use of proprietary format based on geometric properties of kernel. The format does not agree with many system formats. The disagreement makes the usage of the solid models across system gets lacked. To remove this drawback the solid models are used across systems using standard exchange formats. The model exchange formats thus plays a vital role for usage of solid model across systems.Different Model Exchange Formats : It is very vital to have model exchange formats in place to make the use of solid models across systems viable. Such model exchange formats are available in different formats. To name few earlier used model exchange formats are DXF and VDAF. The DXF is the oldest model exchange format and it was used in AutoCAD program. The VDAF was promoted by Germany and was used across industrial systems. The most popular recent model exchange formats are IGES, STL and STEP.
Recent Model Exchange Formats : The recent model exchange formats as mentioned above are IGES, STL and STEP. Let us discuss each of these in detail.
IGES : IGES stands for Initial Graphics Exchange Specification. This model primarily took its presence for contoured surface but later recent versions of initial graphics exchange specification are used even for solid models represented using boundary representation. The initial graphics exchange specification has a formatted file, which represents the surface in analytical representation. It is essential for numerical controlled systems to have accuracy in data presented for surface representation.
If there is even little loss of data in initial graphics exchange specification it becomes unusable in numerical controlled system where accuracy of data for surface is very vital. When there is loss of data users normally tend to update the formatted file of initial graphics exchange specification to cope up the accuracy which involves time and there by loss in productivity.
STL: STL stands for Stereolithography Tessellated Language. This exchange format took its root from prototyping systems and uses triangular facets to store the boundary representation of a solid model. Since this use triangular facets for exchange format it is essential that the whole solid model must be broken by CAD system into number of facets for representing in a format to exchange among various systems. The formatted file in the stereolithography tessellated language has coordinates represented as (x, y, z) to represent each triangular facet.
Though one can have number of facets decomposed into many to have accuracy attained an important note must also taken that greater the faceting higher would be the storage requirements. The stereolithography-tessellated language is most popular exchange format among CAD or CAM users since it is very easy to use. It is normally used in all systems where accuracy is not of much importance. To name one such application is visualizing and analysis programs where accuracy is not of much consideration and so stereolithography tessellated language takes its presence here. However this presentation is not suited for numerical controlled systems where accuracy is much vital.
STEP : STEP is also called as Standard for Exchange of Product data and handles both geometric and non-geometric data associated with a product. International Standards Organization maintains this exchange format.
Many models use one or two-model exchange formats thus making the use of model across systems easier and viable.