What is the deference between solid designing & surface designing ?

Solids modeling

Solids modeling is defining an object with geometric mass. Solids modeling programs usually create models by creating a base solid and adding or subtracting from it with subsequent features. Features such as extrudes, extrude cuts, revolves, radii, chamfers, etc. Examples of solids modeling programs are Solidworks, CATIA, and ProEngineer. It was originally developed for machine design, and is used heavily for engineering with large part assemblies, digital testing and rapid prototyping.

Surface modeling

Surface modeling is defining an object’s exterior with an infinitesimally thin skin. This skin is created by lofts, sweeps, and NURBS curves - i.e. sculptured surfaces with lots of curvature. The surfaces are either defined by poles or guide curves. A surface is considered a solid only when it is completely enclosed. It is used to make technical surfaces (e.g. air plane wing) or aesthetic surfaces (e.g. car’s hood). It was developed for the aerospace and automotive industries in the late70s. Rhinoceros3D and Alias Studio Tools are examples of a surface modeling programs. It is generally considered more difficult than solids modeling, but the models are more robust because the programs aren’t generally feature based. Later changes have to modify the existing geometry as opposed to just editing the original feature, which is more difficult but keeps the model from collapsing when one feature interferes with another.

Creating in specific Dimension for solid modeling

Creating non dimensional parts and irregular shape new component .