Reverse Engineering Summary

Geomet offers many tools to assist in reverse engineering. These tools include feature data point scanning and exporting measured features and data clouds as IGES entities. Capturing data is handled by a wide variety of common sensors from hard probes, electronic touch probes, analog scanning probes to 3D laser scanning probes.

Reverse engineering is designed to provide a detailed explanation of an artifact that may not have nominal data known about it. Identifying prismatic features such as circles, planes, cones and other defined geometric features combined with data clouds can then be exported into a file format that a CAD system could read. The CAD system will then analyze the information and form the solid objects or motion paths for CNC tools.

Summary of Reverse Engineering Tools:
Select Scan Method	Chooses the active Scanning Mode within Geomet.
GeoTracer	Hard Probe drag scanning used on manual CMMs.
Touch Probe Data Clouds	Capturing of discreet data point clouds utilizing manual or DCC CMMs.
Line Scan	Single line capturing of data points under DCC control. The motion path adjusts to perform surface following.
Radius Path Auto Scan	Radial path capturing of data points under DCC control. This is designed to work on ends of cylinders where the path must follow a rim. This tool does not perform a contour following during motion.
4 Point Boundary Surface Scan	Creates a flexible 4 corner boundary that rows and columns of data points will be captured within. Exclusion zones can be defined to eliminate areas that data points should not be captured such as holes or other obstacles. The captured data points conform to a accurate row/column pattern designed for accurate surface fitting. This tool perform contour following.
Radial Boundary Surface Scan	Radial boundary scan is similar to the 4 point boundary scan but uses a diametric border that the rows and columns will be contained.
Cardinal Spline Generation	A cardinal spline is a series of individual curves between points joined to form a larger curve. The spline is specified by an array of points and a tension parameter. A cardinal spline passes smoothly through each point in the array; there are no sharp corners and no abrupt changes in the tightness of the curve. By passing through every point, there are no missed points that can cause errors when fitting a surface over the splines.
Exporting IGES Entities	Export tool used to create a IGES file for use to exchange data with a CAD system, see Supported IGES Entities.

The capturing of data points over an unknown surface utilizing a Coordinate Measuring Machine produces a data point cloud of XYZ values. The values represent the ball center of the stylus attached to the CMM. Touch probes are triggered devices that do not provide information as to the location where on the stylus ball the actual touch of the surface occurred.

Therefore, utilizing the data cloud in reverse engineering requires that the CAD system must perform an offset surface command before the final solid is created. To assist the CAD system, Geomet offers controlled data point collection tools and the exporting of fitted B-Spline Curves through the data points.

Understanding the Data Cloud Structure

Data clouds produced by the 4-Point and Radial Boundary Scan Tools are built on a Row and Column structure that is aligned with the Machine Coordinate System. As shown below in the left example, we are looking directly over the data cloud that was taken on a sphere. The rows and columns are consistent and aligned with the X and Y-axes of the CMMs natural movement. The example on the right shows the same data cloud rotated to show the Z-axis height.

Viewed from +Z	Viewed from +X, -Y, +Z

Another example is a close-up of the fan blade shown in Radial and 4-Point Boundary Scans. When viewed from +Z, the rows and columns are again uniform.

Fan Blade as viewed from +Z

The result of building uniform rows and columns allow for simple building of splines and surfaces when imported into CAD system.