Reverse Engineering

For short-range 3D scanning we use mobile 3D scanners, laser scanners or strip projection scanners.

For short-range 3D scanning we use mobile 3D scanners, laser scanners or strip projection scanners. Laser scanners from Perceptron, Scanworks V4i and V5. Strip projection scanners from Zeiss (Steinbichler), Comet L3D 5M, approved according to VDI/VDE 2634. With these 3D scanners we can digitalize components of almost all sizes. Depending on the measuring volume, the accuracy of the scanners at short range is between approx. 6 µm and 80 µm (individual scan). The scanners work without contact and can usually scan almost all surfaces without object marks. In the following, the workflow of a scanning process during reverse engineering, from the scanned point cloud via the new CAD model to the geometry control (miscolour analysis), is illustrated.
The scanned point cloud of the object to be digitalized is processed with Geomagic Design X (Rapidform XOR) or Geomagic Studio software to create a CAD model. CAD models are created either by exact surface reconstruction or by parametric reconstruction of the model using a 3D CAD system. Both fall within the concept of reverse engineering. The 3D CAD systems that we employ are PTC Creo (Pro/Engineer) and Autodesk Inventor (other CAD systems on request).

WORK FLOW: REVERSE ENGINEERING

Component

Component for which no digital data is available. In this example, 3D CAD data was required for a new production of the 20-year-old casting. The component is optically measured with a 3D scanner. All visible surfaces are recorded.

Component

Step 1

Point cloud: 3D scanning produces a 3D point cloud of the component with countless points. (For a better representation, the point cloud in this picture is strongly thinned out.)

Step 1

Step 2

Polygon area mesh: The point cloud is linked (triangulated). We create a polygonal surface mesh from the point cloud, which consists of numerous small flat triangular surfaces (also strongly thinned out in the image.) The mesh then has to be aligned so that the model has a meaningful position in space relative to the original coordinate system. These polygon meshes form the basis for all further steps in reverse engineering (surface reconstruction) or quality control and inspection projects.

Step 2

Alternative 1 3

Alternative 1: parametric CAD model. A newly constructed, idealized, parametric CAD model with all construction elements and complete model hierarchy. Consisting of control geometry and/or C2 continuous free-form surfaces. The CAD model can be used for all manufacturing processes. Advantages of parametric CAD models: Geometrical changes of the model can be implemented simply and 2D drawings can be derived, which are needed for things such as metal-cutting production.

Alternative 1 3

Alternative 2 3

Alternative 2: exact reverse engineering. NURBS model (Non-Uniform Rational B-Spline) e.g. as STEP data set. The NURBS model is manufactured in the same way as the component, with all production inaccuracies and damages, etc., which we can leave or conditionally repair. A NURBS model does not consist of control geometry, but of free-form surfaces that are formed from four-sided surface patches with continuous transitions. Disadvantage: The creation of production drawings and geometric changes to the model are only possible to a very limited extent. Advantage: Less effort is required than with a parametric CAD reconstruction. We can also create hybrid models, i.e. a combination of parametric CAD model (control geometry) and NURBS model (free-form surfaces). This makes sense if only partial areas with control geometry (e.g. for exact alignment of the component in the CAD system) are required.

Alternative 2 3

Step 4

Geometry check: check of the new CAD data. The CAD data is overlaid with the scan data. On the basis of colours, geometric differences between CAD and scan are then made visible. Green means that the surfaces are within the permitted tolerance. Red means too much and blue too little material or deviation. This type of geometry control, the surface comparison, is also referred to as malcolour or false colour analysis. Intended purpose of the new CAD models: e.g. for reconstruction, machining, the creation of a new casting model, for FEM analyses, for CFD analyses, for a new design, for competitive analysis, for installation space investigations, for digital archiving, etc. We can supply all generated CAD models in the following formats: IGES, STEP, STL, SAT, 3DS, Pro/E, Creo, Inventor, other CAD systems on request.

Step 4

APPLICATION EXAMPLES: Reverse Engineering

Art

3D SCAN MODEL FIGURE OF A FOUNDER

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