Reverse Engineering

Reverse Engineering is the process in which we convert electronic files created by data capture into usable 3D CAD files. With these files, we are able to investigate design intent versus as built, design around existing parts, or even update existing designs.

Understanding usage of captured data and budget will help in choosing your CAD option(s). Below are the main options for 3D CAD files. Sometimes, depending on the fidelity you need for your reverse engineering project, we will mix CAD techniques for your reverse engineering needs, see Hybrid below.

Depending on your reverse engineering needs, the CAD options below have a cost associated with each.

Point Cloud

Point Cloud Reverse Engineering

Point Cloud A point cloud is a set of data points in some coordinate system.

Point clouds may be created by 3D scanners. These devices measure a large number of points on the surface of an object, and often output a point cloud as a data file. The point cloud represents the set of points that the device has measured.

As the result of a 3D scanning process point clouds are used for many purposes, including to create 3D CAD models for manufactured parts, metrology/quality inspection, and a multitude of visualization, animation, rendering and mass customization applications.

While point clouds can be directly rendered and inspected, usually point clouds themselves are generally not directly usable in most 3D applications, and therefore are usually converted to polygon mesh or triangle mesh models, NURBS surface models, or CAD models through a process commonly referred to as surface reconstruction.

There are many techniques for converting a point cloud to a 3D surface. Some approaches build a network of triangles over the existing vertices of the point cloud, while other approaches convert the point cloud into a volumetric distance field and reconstruct the implicit surface so defined through a marching cubes algorithm.

STL Model

STL model Reverse Engineering

STL (STereoLithography) is a file format native to the stereo lithography CAD software created by 3D Systems. STL is also known as Standard Tessellation Language. This file format is supported by many other software packages; it is widely used for rapid prototyping and computer-aided manufacturing. STL files describe only the surface geometry of a three dimensional object without any representation of color, texture or other common CAD model attributes. The STL format specifies both ASCII and binary representations. Binary files are more common, since they are more compact

An STL file describes a raw unstructured triangulated surface by the unit normal and vertices (ordered by the right-hand rule) of the triangles using a three-dimensional Cartesian coordinate system. STL coordinates must be positive numbers, there is no scale information, and the units are arbitrary

Nurbs Model

Nurbs model Reverse Engineering

Non-uniform rational basis spline (NURBS) is a mathematical model commonly used in computer graphics for generating and representing curves and surfaces. It offers great flexibility and precision for handling both analytic (surfaces defined by common mathematical formulae) and modeled shapes.

NURBS are commonly used in computer-aided design (CAD), manufacturing (CAM), and engineering (CAE) and are part of numerous industry wide standards, such as IGES, STEP, ACIS, and PHIGS. NURBS tools are also found in various 3D modeling and animation software packages.

They can be efficiently handled by the computer programs and yet allow for easy human interaction. NURBS surfaces are functions of two parameters mapping to a surface in three-dimensional space and is essential for reverse engineering. The shape of the surface is determined by control points. NURBS surfaces can represent simple geometrical shapes in a compact form. T-splines and subdivision surfaces are more suitable for complex organic shapes because they reduce the number of control points twofold in comparison with the NURBS surfaces

CAD Model (Smart & Dumb)

CAD model (Smart & Dumb) Reverse Engineering

Solid modeling is a consistent set of principles for mathematical and computer modeling of three-dimensional solids. Solid modeling is distinguished from related areas of geometric modeling and computer graphics by its emphasis on physical fidelity (Shapiro, Vadim, 2001). Together, the principles of geometric and solid modeling form the foundation of computer-aided design and in general support the creation, exchange, visualization, animation, interrogation, and annotation of digital models of physical objects.

Parametric (Smart) models use parameters to define a model (dimensions, for example). Examples of parameters are: dimensions used to create model features, material density, formulas to describe swept features, imported data (that describe a reference surface, for example). The parameter may be modified later, and the model will update to reflect the modification. Typically, there is a relationship between parts, assemblies, and drawings. A part consists of multiple features, and an assembly consists of multiple parts. Drawings can be made from either parts or assemblies.

Solid (Dumb) models have no defined parameters. The file output is either in a step/iges format.

Hybrid

Hybrid Reverse Engineering

Hybrid modeling is what we output when we merge nurbs and CAD together to obtain a certain outcome; depending on budget and use of model typically in your reverse engineering project.

One area this is useful is when building castings, where as the nurbs model makes up the casting, and the machined features are then modeled with design intent. This way, the customer gets a highly accurate model, lower cost, and machinable.

This is also good when one needs a model to use in designs, knowing the model will not change, but needs to mate the CAD in an assembly. By adding mounting geometry such as planes and cylinders, the engineering can get a low cost model he can use to design around.

Features Only Model

Features only model Reverse Engineering

We sometimes have customers request only features of a scan. This can include planes, axii, cylinders, points, and profiles. This is a very low cost way of capturing a ton of data when one does not need the entire model.

Think about scanning a chassis. You do not necessarily need the body. Perhaps you are puting a hotrod on an S10 chassis and you just want the mounting points. This would be much cheaper than modeling the entire chassis.

Section Slices

Section slices Reverse Engineering

We can provide section slices of a scan. This is lighter weight curves that can be imported into any 3D CAD system. This is a very quick and easy way to import a lot of scan data into a design.

Although the 2D slices are highly accurate, using it in CAD can tend to be tedious, as it sometimes gets a little confusing about what curve you are working with.

Color Map PDF

Colormap 3D pdf Reverse Engineering

Colorpmapping is used to compare more than one 3D math file. This helps ensure the CAD model truly represents the scanned part.

This is a huge benefit over using calipers and a tape measure, when more accuracy is needed.

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