Reverse EngineeringFeature based solid modeling, parametric modeling & rapid surfacing
3D scanning is generally the first step in reverse engineering complex parts. The ultimate goal of reverse engineering is generally to create a 3D CAD (Computer Aided Design) model for use in the customer’s design system. There are several types of models that can be generated from 3D scanned data.
Parametric Solid Model
A parametric model is composed of primitive geometric features, trimmed surfaces, fillets & radii. Geometry is developed using traditional solid modeling techniques such as sketching and extruding, using the underlying scanned data as a reference. Entire model history is transferred into Solidworks upon completion in order to facilitate future design changes.
File Format: Solidworks (sldprt)
Feature Based Solid Model
A feature based model is composed of primitive geometric features, trimmed surfaces, fillets & radii. Geometry is developed using traditional solid modeling techniques such as sketching and extruding, using the underlying scanned data as a reference. Original feature geometry may be extracted after import into customer CAD system. The only difference between a feature based model and a parametric model is that the Parametric model contains model history, and the feature based model does not.
File Format: iges, step, parasolid, Solidworks (sldprt)
Rapid Surface Model
A rapid surface model is developed using a quilt of smooth NURBS surface patches that are “shrink-wrapped” onto the polygonal mesh to create a model suitable for import into CAD. Upon CAD import, surfaces are knit together to form a static, or non-parametric solid. Rapid surface models are useful for highly complex shapes such as organic forms, art & sculpture or intricate castings. This technique is not generally recommended for mechanical components with a lot of geometric features.
File Format: iges, step, parasolid, Solidworks
A hybrid model will contain characteristics of both a Feature Based Model as well as a Rapid Surface Model. It is developed using a variety of techniques in order to develop a model that has both mechanical as well as free-form or organic geometric features.
A polygon mesh can either be the starting point or end result of a 3d scanning or reverse engineering project. Raw data from most scanners today is export as a polygon mesh in STL or OBJ format. These data sets are often used as the starting point for CAD modeling. However, it is interesting to note that mostly all 3D printers operate using polygonal meshes in STL format. This mesh must be “water tight”, with no holes or defects. As such, raw scanned data must be post processed to some degree in order to generate a printable file.
File Format: STL, OBJ, VRML, PLY