Reverse Engineering (RE) Reverse Modeling Technology

Geometric modeling technology has been widely used in product development and manufacturing. However, for various reasons, there are still many products that are not described by the CAD model, and the design and manufacturer are facing the physical samples. In order to adapt to the development of advanced manufacturing technology, it is necessary to convert these physical objects into CAD models, so that they can be processed using advanced technologies such as CAD and CAM. At present, technologies related to the techniques used to obtain product mathematical models from physical samples have developed into a relatively independent category in CAD and CAM, called reverse engineering ). By reverse engineering, the CAD model of physical objects is reproduced, so that the products based on physical objects may make full use of advanced technologies such as CAD and CAM in the design and manufacturing process. Because the implementation of reverse engineering can accurately and reliably copy physical samples within a short period of time, reverse engineering has become one of the hot topics of advanced manufacturing technology. Using some non-professional reverse design software (such as UG, Pro/Engineer, and CATIA) and some professional reverse design software (such as surfacer, copycad, and trace) reverse Modeling is a typical example of reverse engineering application in enterprises.
Due to the needs of the company's new product development, I use ugsoftware to reverse engineer parts in the reverse shape of complex automotive stamping parts to achieve better application results. The measuring equipment we choose is the Coordinate Measuring Machine of LK, which can be used to measure the spatial coordinate, scanning profile, measurement parting line and contour line of features. The data size obtained by this device is not as big as that scanned by a laser scanner, so it is appropriate to use some non-professional reverse design software. The Reverse Modeling of UG follows the general principles of point, line, face, and body.
I. measurement points
Plan how to hit the site before measuring points. The designer puts forward the curved surface hitting requirements. The general principle is to keep the point secret when the curvature changes greatly, while the smooth area can be thinner. Generally, the efficiency of the Coordinate Measuring Machine is much lower than that of the laser scanner. It is worth noting that in addition to scanning the profile and testing the parting line, the feature lines such as the contour line are also necessary, which will bring convenience in the construction.
Ii. Connection
(1) sort out the link before sorting out the link, including removing the Mistaken Point and obvious defect points. The Section points in the same direction are placed in the same layer. The parting line points and hole points are placed on one layer separately, and the contour points are also placed on one layer separately for ease of management. Generally, this work can be completed in the measurement point phase or ugsoftware. Generally, the measurement software can pre-set the placement layer of the point, one side of the measurement point, one side of the arrangement.
(2) try to minimize the error and smooth the parting line points of the dot link. In many cases, the parting line is the assembly line of the product. For general parts of automobiles and motorcycles, the error of the link is generally controlled below 5mm. The line should be targeted, and the surface construction method should be roughly determined based on the shape and characteristics of the sample, so as to determine which lines need to be connected and which lines do not need to be connected. The line can be a straight line, an arc, or a spline ). The most common method is spline. The "through point" method is used. The point selection interval should be as even as possible. When there is a rounded corner, ignore it first to make it a sharp corner. After the surface is finished, round the corner.
(3) curve adjustment due to measurement errors and the surface of the sample is not smooth, the variation of the curvature radius of the connected spline often changes suddenly, which affects the smoothness of the subsequent construction. Therefore, the curve must be adjusted to make it smooth. The most common method to adjust is edit spline. Select the edit pole option and drag the control point with the mouse. There are many options, such as limiting the movement of control points in a certain plane, moving to a certain direction, whether it is a rough or fine tune, and opening the "comb" switch that shows spline. In addition, adjusting spline often requires moving an endpoint of spline to another point, so that the curve of the built surface has a point of intersection. However, no matter what command is used to adjust the curve, there will be deviations. The more adjustment times, the larger the cumulative error. The allowable error value is determined by the specific requirements of the sample.
3. Structure
Use a variety of surface construction methods to create a surface, including though curve mesh, though curves, rule, swept, and from point cloud. The selection of the surface construction method depends on the specific characteristics of the sample. The most common method is the though curve mesh, which uses this command to weave the adjusted curve into a surface. The advantage of the though curve mesh is that it can ensure the continuity of the Surface Boundary Curvature, because the though curve mesh can control the surrounding Boundary Curvature (tangent), so the quality of the surface is higher. Though curves can only ensure the curvature of both sides, and the error is also large in the face construction. If the intersection of the two curved surfaces needs to be rounded, because the boundary of the though curve mesh is the intersection of the two curved surfaces, this line is obviously smoother than that of the two though curves curved surfaces, in this way, the quality of the blend rounded corner is different.
When you are a beginner in Reverse Modeling, there is often a "crease" between the two sides, which is mainly caused by the non-tangent of the two sides. To solve this problem, you can adjust the tangent between the endpoint of the though curve mesh curve and the corresponding curve in the other surface, plus the though curve mesh boundary tangent option. Surface tangent can be ensured only when the curve is tangent.
In addition, when creating a single and relatively flat surface, it is more convenient to directly use a point cloud (from point cloud. However, this method is not applicable to curved surfaces with large curvature radius variation and has a large error in surface construction. Sometimes the gap between the surface and the surface must be bridge to ensure smooth transition of the surface.
In the process of building a surface, sometimes some lines need to be added for surface construction. The connections and planes are often alternating. After the surface is built, check the surface error. Generally, the measurement point-to-surface error is required. Check the smoothness of the surface for the surface with high appearance requirements. When a surface is not smooth, you can find some sections on the surface, adjust these sections to make them smooth, and use these sections to reconstruct the surface. This is a common method.
The structure must be concise. The surface should be as big as possible, with few sheets and not too broken. This will help to add some features such as rounded corner, slope, and thickening at the end of the page, and also facilitate the next step of programming and processing, and reduce the computational workload of the knife path, the NC file is small.
Iv. Structure
After the external surface is complete, the next step is to build an entity model. When the model is relatively simple and the external surface quality is relatively good, you can use the suture thickening command to create an object. But in most cases, it cannot be thickened, so only the offset outer surface can be used. You can use the offset command to select multiple faces at the same time or select all faces in the window, which improves the efficiency. Learn to analyze the causes of surfaces that cannot be offset. One possible reason is that the curvature of the surface is too large, and the offset will be self-Intersecting, resulting in offset failure (some software algorithms are different from this algorithm, for example, the rhinoceros can offset the surfaces that will generate self-intersection), such as small rounded corners. Another possibility is that the quality of the Offset surface is poor, with local ripple, in this case, only the curved surface can be modified before the offset; there are some surfaces that seem to be smooth, but they cannot be offset. In this case, you can use Extract geometry to form a B surface, and then offset, it will basically succeed. Some of the curved surfaces after the offset need to be cropped, some need to be masked, and various surface editing methods are used to construct the inner surface, and then the inner and inner surfaces are stitched into a solid (solid ). Finally, design the product structure, such as reinforcing bars and installation holes.
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Reverse Engineering, also called reverse engineering, is reverse engineering.
It refers to the collection of a large number of three-dimensional coordinate points from the object, and thus the establishment of the geometric model of the object, and then the development of advanced technology of similar products. Reverse engineering is the opposite of a general design and manufacturing process. A model is built upon a physical object. Profile-based processing is a typical reverse engineering application. At present, the application of reverse engineering and reverse engineering has evolved from simple and manual operations to the use of advanced computers and measuring equipment for design, analysis, manufacturing, and other activities, such as obtaining the shape of the mold after model repair, analyzing the physical model, innovative design based on existing products, and fast profile manufacturing.
In general, in a sense, reverse engineering is an imitation. The premise here is that our traditional design and manufacturing is "positive Engineering (of course, there is no such statement)" by default )".
The reverse engineering of a software is an analytical program, which tries to establish a program's representation process at a higher abstraction level than the source code. Reverse Engineering is the design recovery process. Reverse engineering tools can extract data structures, architectures, and program design information from existing programs.
Introduction to four major Reverse Engineering Software
Imageware
Imageware is the most famous reverse engineering software developed by EDS. It is widely used in automobile, aviation, aerospace, consumer appliances, molds, computer parts and other design and manufacturing fields. The software has a large user base, including BMW, Boeing, GM, Chrysler, Ford, raytheon, Toyota, and other famous international companies outside China, there are major enterprises in China, such as Shanghai Volkswagen, Shanghai Jiao Tong University, Shanghai DELPHI, and Chengdu Aircraft Manufacturing Company.
In the past, this software was mainly used in the aerospace and automotive industries. Because these two fields have high requirements on aerodynamic performance, we must carefully consider aerodynamic power at the beginning of product development. The conventional design process first designs the structure according to the Industrial Modeling needs, creates the oil mud model, and sends it to the wind tunnel lab to measure the aerodynamic performance, then, the model is repeatedly modified based on the experiment results until satisfactory results are obtained. The final sludge model obtained is the model that meets the needs. Reverse engineering software is required to accurately input the shape of the sludge model into the computer as an electronic model. First, use a three-coordinate measuring instrument to measure the model surface lattice data, and then use reverse engineering software (for example, Imageware surfacer) for processing to obtain the class 1 surface.
With the advancement of science and technology and the increasing consumption level, many other industries have begun to adopt reverse engineering software for product design. Taking the mouse tool manufactured by Microsoft as an example, in terms of its function, you only need three buttons to meet your needs. However, how can we make the mouse feel the best, after a long period of use, it is not easy to produce fatigue, but it is a problem that the manufacturer must seriously consider. Therefore, Microsoft first created several models based on ergonomics and submitted them to the user for evaluation. Then, the model was directly modified based on the evaluation opinion until everyone was satisfied with the modification, finally, we use reverse engineering software Imageware to generate CAD data. After the product is pushed to the market, due to its novel appearance, smooth curves, and a good feel, it conforms to the ergonomics principle, so it is quickly recognized by users and the market share of the product has increased significantly.
Main products of Imageware reverse engineering software include:
Surfacer-reverse engineering tools and class 1 Surface generation tools
Verdict-comparison and evaluation of measurement data and CAD data
Build it-provides real-time measurement capability to verify the product's manufacturing
Rpm-generate quick prototyping data
View -- similar to verdict, it is mainly used to provide 3D reports.
Imageware adopts the nurb technology, which features powerful software and is easy to use. Imageware has low hardware requirements and can run on a variety of platforms: UNIX workstations and PCs. The operating system can be UNIX, NT, Windows95, and other platforms.
Due to its technical advancement in reverse engineering, Imageware has occupied a large market share since its launch, and the software revenue is growing rapidly at an annual rate of 47%.
Surfacer is the main product of Imageware and is mainly used for reverse engineering. Its data processing process follows the point-curve-surface principle. The process is simple and clear, and the software is easy to use. The process is as follows:
I. Point Process
Read the dot matrix data.
Surfacer can receive almost all coordinate measurement data and other formats, such as STL and VDA.
Align the separated lattice (if needed ).
Sometimes, due to the complex shape of the parts, a single scan cannot obtain all the data, or a large part cannot be completed at a time. This requires moving or rotating the parts, which leads to a lot of separate lattice. Surfacer can use special point information such as the cylindrical surface, sphere, and plane to accurately align the dot matrix.
Determine the dot matrix to remove noise points (Measurement Error points ).
Due to the limitation of measurement tools and methods, there may be some noise points. surfacer has many tools to judge the lattice and remove the noise points to ensure the accuracy of the results.
Use Visual dot matrix observation and judgment to plan how to create a surface.
A part is composed of multiple separate surfaces. For each surface, you can determine the method used to construct it based on the characteristics. For example, if a surface can be directly generated from a grid of points, you can consider using this dot matrix directly. If a surface requires multi-segment curve skin, you can consider intercepting the segment of the point. Planning in advance can avoid detours in the future.
Create a grid or segment of a vertex as needed.
Surfacer provides many grid and point segmentation tools for generating points. These tools are flexible and convenient to use, and can also generate segments of multiple points at a time.
Ii. Curve creation process
Determine and decide which type of curve to generate.
The curve can be accurate through the dot matrix, or it can be very smooth (capture the main shape of the curve represented by the dot matrix), or between the two.
Create a curve.
Create a curve as needed. You can change the number of control points to adjust the curve. When the number of control points increases, the shape is well consistent, and when the number of control points decreases, the curve is smoother.
Diagnose and modify curves.
The smoothness of a curve can be determined by the curvature of the Curve. the smoothness of the curve and the dot matrix can be checked, and the continuity (connection, tangent, and curvature continuity) between the curve and other curves can be changed ). Surfacer provides many tools to adjust and modify curves.
3. Create a surface
Decide which surface to generate.
Like a curve, you can consider generating a more accurate surface, a more smooth surface (such as a class 1 surface), or both, depending on the product design needs.
Create a surface.
There are many ways to create a surface. You can use a dot matrix to directly generate a surface (Fit free form). You can use a curve to generate a surface through skin, sweep, and four border lines, you can also create a Surface Based on the dot matrix and curve information. You can also generate a surface through other such as the garden angle and bridge surface.
Diagnose and modify a surface.
Compare the degree of fit between the surface and the dot matrix, check the smoothness of the Surface and Its continuity with other surfaces, and modify the surface. For example, you can align the surface with the dot matrix, you can adjust the control points of a surface to make the surface smoother or reconstruct the surface.
Chris Chatburn, design engineer at Triumph Motorcycles, UK, said: "With Surfacer, we can complete more design cycles in a shorter time, which will reduce our design time by 50%."
The latest Surfacer 10.6 software integrated the High-Performance Tools for the following workflow:
[Elastic surface creation tool]: it allows you to easily create a surface from a curve, surface, or measurement data in an elastic design environment. It supports bejiel) and non-even rational B-spline surface. You can select an appropriate surface method to benefit from combining the advantages of the two methods.
[Dynamic surface modification tool]: allows users to test the design of themes in an interactive manner, and immediately shows whether the appearance and ideas are in line with engineering concepts. The design, engineering analysis, and manufacturing standards are all taken into account through the careful construction process. Therefore, each time you modify a surface, you do not need to re-check the standards.
[Real-time curved surface diagnostic tools]: provides multiple methods, such as continuity of any section, reverse radiation of a curved surface, high-brightness line, spectral diagram, and reflective diagram under the radiation of a column-shaped light source of a curvature cloud map, surface Defects can be identified at any time of design.
[Effective Curved Surface continuity management tools]: even if the curved surface is moved or modified during complex surface patching, the curvature continuity between the curved surface and the connected curved surface can be ensured, this avoids tedious manual re-adjustment.
[Powerful data processing and scanning capabilities]: According to the Rainbow Graph Method (equivalent to assuming that rain falls from the top, rain flow rate varies due to shape differences), curvature size change cloud map method (for a completely smooth class 1 surface, equivalent to the curvature size change to zero, for two different surfaces, this value will be different) will scan data separately, in this way, the main features of the product can be quickly captured, and various corresponding surfaces can be quickly created to avoid trouble analysis and processing.
It is precisely because Imageware has powerful functions unmatched by other software in computer-aided surface check, surface modeling and quick samples that it deserves to become a leader in the field of reverse engineering.
Geomagic Studio
Geomagic studio, a reverse engineering and 3D detection software developed by raindrop, allows you to easily create a perfect polygon model and mesh from the point cloud data scanned, it can also be automatically converted to a green surface. This software is also the most widely used reverse engineering software except Imageware.
Geomagic studio consists of five modules: qualify, shape, wrap, decimate, and capture. Main functions include:
Automatically converts point cloud data to polygons)
Decimate)
Convert a polygon to a green surface
Surface Analysis (tolerances, etc)
Output file formats that match the CAD, cam, and CAE formats (such as IG, STL, and DXF)
1. Product Model Obtained from the CAD model
2. Read the CAD model into geomagic Studio
3. CAD design model and point cloud data scanned from the actual model (different coordinate systems)
4. automatic matching between scanned data and CAD models
5. Automatic Alignment of scanned data and CAD models
6. The error is visually displayed in a color image.
7. the user can mark the error as an Italian point
8. The qualify result can be output in HTML format.
Copycad
Copycad is a powerful reverse engineering system software developed by delcam, UK. It can generate 3D CAD models from existing parts or entity models. This software provides a complex tool for the generation of CAD surfaces from digital data. Copycad is able to receive data from Coordinate Measurement Machine Tools while tracking machine tools and laser scanners.
CopyCAD's simple user interface allows users to make production in the shortest time and quickly master its functions, even for the first time users. CopyCAD allows users to quickly edit digital data and generate high-quality complex surfaces. The software system can completely control the selection of the surface boundary, and then automatically generate multiple smooth surfaces based on the preset tolerances. At the same time, CopyCAD can ensure the continuity of the tangent between the connected surfaces.
The main functions of the software are as follows:
Digital point data input
DUCT graphics and triangle model files
CNC Coordinate Measuring Machine
Separate ASCII code and NC file
Laser scanners, 3D scanners, and SCANTRON
PC ArtCAM
Renishaw MOD file
Point Operation
Allows you to add, subtract, delete, move, and edit vertices, such as point hiding and tagging.
The ability to compensate for the three-dimensional bias of the model for the size of the measurement Probe
Ability to convert models, such as scaling, rotating, and mirroring
Ability to crop a plane, polygon, or other models.
Triangle Measurement
Triangular measurements of digital models within user-defined tolerances and options, including:
① Original -- normal settings
② Sharpness-acute Feature Enhancement
③ Feature matching-features from point normal data
④ Disable triangle measurement-you can disable the model for quick plotting.
Feature line generation
Border -- transform the outer edge of the model to the feature line
Intermittent-Detects sharp edges in data to find simple features (such as protruding and concave)
Ability to convert digital scanning lines to feature lines
Input data-the ability to extract multiple lines and splines from the dot File
Surface Construction
Multiple curved surfaces are generated by tracking straight lines in the triangle measurement model.
Between connected surfaces, use an existing surface to define the tangent continuity boundary with options
Use feature lines to guide and accelerate surface Definition
Curved Surface Error Check
Comparison of surface and digital point data
Report maximum limit, median and standard error Deviation
Displays changes in an incorrect image.
Output
IGES, CADDS4X
Stl ascii code and binary
DUCT graphics, triangle models, and surfaces
Separated ASCII code
RapidForm
RapidForm is one of the four major reverse engineering software products in the world produced by South Korea's INUS company. RapidForm provides a new generation of operation mode, which allows you to calculate point cloud data in real time to generate a polygon surface without seams, makes it an optimized interface for 3D Scan post-processing. RapidForm will also improve your work efficiency, expand the application scope of 3D scanning devices, and improve the scanning quality.
Multi-point cloud data management interface
Advanced Optical 3D scanners produce a large amount of data (up to 100,000 ~ 200,000) because the data is huge, expensive computer hardware is required for computing. Now RapidForm provides Memory Management Technology (using fewer system resources) to shorten your data processing time.
Multi-Point Cloud Processing Technology
It can quickly process a large volume of point cloud data, and can be easily converted to a very good point cloud, whether it is a sparse point cloud or a skip point, rapidForm provides a tool for filtering point clouds and techniques for analyzing surface deviations to eliminate undesirable point clouds generated by 3D scanners.
Calculation of converting a quick point cloud to a polygon surface
Among all reverse engineering software, RapidForm provides a special computing technology. For 3D and 2D processing, RapidForm provides the fastest and most reliable computing method, you can quickly calculate a polygon surface from a point cloud. RapidForm can process unordered point data and ordered point data.
Color point cloud data processing
RapidForm supports color 3D scanners, which can generate optimized polygon and map color information to the polygon model. During the surface design process, the color information is completely stored, and the RP molding mechanism can be used to create a model with color information. RapidForm also provides the color function. With the real-time color editing tool, you can directly edit your favorite color for the model.
Point Cloud Merging
Scanning data from multiple points may be manually combined with special point clouds. Of course, RapidForm also provides a technology that allows users to easily merge various types of point cloud data.
Note: The PixForm software attached to the Roland mold processing machine is the OEM software of RapidForm.

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