Reverse Engineering: Generation of Cad Model from Scanned Mesh File Captured using 3d Scanner

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Reverse Engineering: Generation of Cad Model from Scanned Mesh File Captured using 3d Scanner

Shaik Feroz1

Research Scholar, Department of Mechanical Engineering, VFSTR, Vadlamudi, Guntur 52213,

India.

Dr. M. Ramakrishna

Department of Mechanical Engineering, VFSTR, Vadlamudi, Guntur 52213, India.

Dhaval Varma P.

Department of Mechanical Engineering, VFSTR, Vadlamudi, Guntur 52213, India.

Abstract:- Reverse Engineering is the method of capturing an existing objects physical characteristics and reproducing a replica of it from the extracted data. This technique is widely recognized as a predominant technique in aerospace design & manufacturing. It is hard to reproduce a duplicate of any part or model the part when original designs are not available specifically in the case of legacy aircrafts. In this technique, various stages involved are data acquisition (scanned mesh file) using 3D scanning, feature extraction, segmentation to fit free form shapes and developing a 3D CAD model. This research paper signifies the role of reverse engineering in restoring the legacy features of aircraft components especially for an aging fleet.

Keywords: Reverse Engineering, 3D scanning, mesh file, CAD, free form shape

1. INTRODUCTION

The modern aerospace industry has an edge due to the substantial developments during the world wars. One of the major issues encountered by the aircraft manufactures is to restore the crucial design data of the older aircrafts that is lost over the years. To overcome this issue many aerospace companies are utilizing the reverse engineering technique to restore the data of legacy parts on digital platform. Further, this digital data is made compatible to the CAD requirements, which plays a vital role in subsequent manufacturing of aerospace components. The other reasons for using reverse engineering in aerospace industries are:

  1. To retrieve the data for manufacturing.
  2. To easily model, the complicated parts with intricate shapes.
  3. Inspection and comparison for error analysis.
  4. Development of new/customized parts based on existing parts with no designs.Reverse engineering is widely in use to produce various complicated aircraft parts and assemblies. It has also played a vital role in new product developments in different sectors including consumer electronics, automotive industry, medical devices, sporting equipment, toys and in making of jewellery. SME quotes reverse engineering as starting with a finished product or process and working backward in logical fashion to discover the underlying new technology [2]. The part, which was produced using reverse engineering technique, must be in compliance with the requirements, which are present in applicable program criteria.
    1. WORKING PRINCIPLE OF SCANNERThe object is recreated digitally with the help of 3D scanners in which millions of X, Y & Z coordinates (points) are captured all over the physical object by sensing the laser line reflection by 3D scanners. All scanners project lasers on the target and capture the points in relation to its position with respect to the part. When the scanner moves to new location on the part, it captures another set of points and its position. This process continues throughout the scanning process. To establish the relation between data captured at each instant and to align properly, scanner has to know its relative position at each instant with respect to part,

      this is known as 3D positioning system. There are several 3D positioning techniques used by different self-positioning 3D scanners but the break through technique is the usage of targets (in circular shape) on and around the part. These targets are specifically designed to detect easily by the scanner. By measuring distance between the targets, the scanner would know exactly where it is in the space the whole time during the scanning process thereby establishing the relation between the data captured. This is the only method reliable enough to deliver better quality output.

      Data from physical part can be acquired from single point measurement devices such as contact based portable CMM, laser trackers or non-contact high density digitizers such as laser scanners.

      Contact Based

      A contact based measurement device is a system that operates by targeting or measuring one or several points on the component. These points can be measured by means of mechanical methods using ruby probe mounted on portable CMM or optical methods using laser trackers/radars. With these measuring devices as the density of points captured is low density and accurate, this method is highly suitable for inspecting large and complex aero-structure parts rather to reverse engineer them. The output of this method would be points with x, y, z coordinates and directional vectors.

      Non-Contact Based

      This measurement device uses a system of projecting a beam of laser lines on to the surface of interest and captures millions of points in a second, in this way we can acquire high density point cloud for needs. With these measuring devices as the density of points is high, this scanned data can be used forInspection (CAD Comparison, dimensional analysis, GD&T etc.) also we can use this to create technical surface in absence of digital data of the component. The output of this method would be point cloud.

      This paper proposes a 3D non-contact scanning technique using a self-positioning 3D scanner and relatively better approach for digitizing the complex parts. We have modelled a machined sample part using this technique. Using this technique we can model aerospace components.

    2. REVERSE ENGINEERING PROCESS STEPS
        1. Digitizing the partThe sample part considered in this activity is a machined sample part. The part was 3D scanned using portable handheld self- positioning 3D scanner manufactured by CreaForm compatible with VX elements software. Trigonometric triangulation is a process used by 3D scanners (laser based) to accurately capture a 3D shape in the form of millions of points as a point cloud per second during scanning. Within this point clouds, each three points connect and forms a triangle and combination of these triangles form a mesh called as triangulation mesh. This polygonal file is also known differently as polygonal model, Stereolithography Tessellation Language (STL file). This output file can also be used as an input for 3D printing, rapid prototyping, analysis etc.

          Figure 1.Scanning of part

        2. 3D modelling of the Polygon mesh/STL data

      The major steps involved in the conversion to final 3D model are as follows:

      • The part STL data has the coordinate system arbitrary to the geometry to the part; this coordinate system is to be moved in relation to the part using the Polyworks Inspector software.Figure 2. Creating part defined coordinate system
      • This fixed mesh data is imported to PolyWorks Modeler software where this file is optimized using the polygonal editing tools for filling holes, cleaning the boundaries, etc.Figure 3. Optimized Mesh Data
      • After Optimization, NURBS (Non-Uniform Rational B-Splines) curves are laid down first on the polygonal model to determine where the surfaces are to be fitted and then they are automatically intersected to form an N-sided or four-sided trimmed NURBS patches.Figure 4. Creation of NURBS Patches
      • From the NURBS Curves NURBS Patches are created.
      • And then there are several analysis tools are available o check fitment of the generated surface to scan data and also check positional and tangential deviations.Figure 5. Creation of NURBS Surfaces
      • Then fitted Patches converted to NURBS surface, then are exported to STEP or IGES files and are directly imported into CAD/CAM application for further usage.
      • These surfaces can be edited and optimized in any modeling software.Figure 6. Final model in CAD

        3.3. Abbreviations and Acronyms

        STL: Stereo lithography Tessellation Language CMM: Coordinate Measuring Machine

        SME: The Society of Manufacturing Engineers NURBS: Non-Uniform Rational B-Splines 3D: 3-Dimensional

        CAD: Computer Aided Design

        GD&T: Geometric Dimensioning and Tolerance

    3. CONCLUSIONS

During this activity, features of a machined sample part has been successfully captured through 3D Laser scanning and created the 3D model compatible to use with any 3D modelling softwares.This same method can be used to restore the parts of an aircraft and 3D can be created.

Figure 7. From scanning to final CAD generation

  • Reverse Engineering (3D scanning to CAD file generation) reduces huge amount of time, cost and work force involved in product development cycle.
  • The accuracy of surfaces can be improved further through CAD softwares.
  • Quality of the scanned surface generated depends upon the complexity of the part.

ACKNOWLEDGMENT

We would like to thank Mr. Myskar Bhaskar, Application specialist, Polyworks India, whose valuable suggestions were helpful for us and for clarifying our queries regarding this research work.

CONFLICTS OF INTEREST

The authors declare no conflict of interest.

REFERENCES

  1. Kumar, Atul, Pramod Kumar Jain, and Pushparaj Mani Pathak. “Reverse engineering in product manufacturing: an overview.” DAAAM international scientific book (2013): 665-678.
  2. Reverse Engineering Technology of Reinvention, Taylor and Francis Group, LLC International Standard Book No-13: 978-1-4398-0631-9.
  3. Raja, Vinesh, and Kiran J. Fernandes, eds. Reverse engineering: an industrial perspective. Springer Science & Business Media, 2007.
  4. Manzoor Hussain, M., C. H. Sambasiva Rao, and K. E. Prasad. “Reverse engineering: Point cloud generation with cmm for part modeling and error analysis.” ARPN Journal of Engineering and Applied Sciences 3.4 (2008): 37-40.
  5. Singh, Niranjan. “Reverse Engineering-A general review.” International Journal of Advanced Engineering Research and Studies 2 (2012): 24-28.
  6. Bardell, R., V. Balendran, and K. Sivayoganathan. “Accuracy analysis of 3D data collection and free-form modelling methods.” Journal of Materials Processing Technology 133.1-2 (2003): 26-33.
  7. Varady, Tamas, Ralph R. Martin, and Jordan Cox. “Reverse engineering of geometric modelsan introduction.” Computer-aided design 29.4 (1997): 255-268.
  8. Ma, W. Y., and J-P. Kruth. “NURBS curve and surface fitting for reverse engineering.” The International Journal of Advanced Manufacturing Technology 14.12 (1998): 918-927.
  9. Son, Seokbae, Hyunpung Park, and Kwan H. Lee. “Automated laser scanning system for reverse engineering and inspection.” International Journal of Machine Tools and Manufacture 42.8 (2002): 889-897.

REVERSE ENGINEERING: GENERATION OF CAD MODEL FROM SCANNED MESH FILE CAPTURED USING 3D SCANNER

Highlights:

  1. A 3D non-contact scanning technique using a self-positioning 3D scanner (Creaform scan 3D scanner) for digitizing the sample machined part was used in here.
  2. Part defined coordinate system was created using Polyworks Inspector software.
  3. NURBS curves were created after optimization, which were intersected to form NURBS patches.
  4. These surfaces can be edited and optimized in any modeling software.

Shaik Feroz:

He is currently pursuing Ph.D. at Vignan’s Foundation for Science Technology and Research, India. He is having an extensive (13 years) experience in Industry/Teaching, product development, operations and manufacturing management in Aerospace/Mechanical engineering industry. Has strong technical knowledge, passionate about quality, improving efficiency. His research interests include Carbon composites, OOA Technology, Nano Technology, Nano composite, Development of Composite Materials for High performance Applications for Aerospace.

Dr. M. Ramakrishna

Dr. Ramakrishna Malkapuram is currently working as a Professor in the Department of Mechanical Engineering, Vignan’s Foundation for Science Technology and Research, India. His research interests includes Nano Technology, Nano composite, Development of Composite Materials for High performance Applications, Development of eco friendly composite materials, Engineering Plastics, Polymers for Agricultural and Textile Applications, Making use secondary fibers in composites for various low cost Applications. He has authored many research articles/books related to Nano Technology, Nano composite, Development of Composite Materials for High performance Applications, Making use secondary fibers in composites for various low cost Applications etc.

Dhaval Varma Peruri

Dhaval Varma Peruri just completed his B. Tech. in Mechanical Engineering from Vignan’s Foundation for Science Technology and Research, India. He has done his internship at TATA Lockheed Martin Aero structures Ltd, Hyderabad. He is interested in the field of composites, CAD/ CAM. He is having two publications in the field of composites.

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