[pic] Reverse Engineering a New Trend in Manufacturing
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Authors
T.Dhamotharakumar* N.S.Ramesh* dhamotharan007@gmail.com nsrmechanical@gmail.com
* Under graduate Student, K.S.R. College of Engineering, Tiruchengode
Department of Mechanical Engineering
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Abstract

With the significant capital investment in new equipment being placed into out years, more systems need to be maintained in their present condition for longer periods of time. There are often gaps in the technical support information needed to maintain a system built from older designs using outmoded or updated techniques or materials. In some situations, designers give a shape to their ideas by using clay, plaster, wood, or foam rubber, but a CAD model is needed to enable the manufacturing of the part. As products become more organic in shape, designing in CAD may be challenging or impossible. There is no guarantee that the CAD model will be acceptably close to the sculpted model. Reverse engineering provides a solution to this problem because the physical model is the source of information for the CAD model. This is also referred to as the part-to-CAD process.
"Reverse Engineering is the process of taking a finished product and reconstructing design data in a format from which new parts or molds can be produced."-The Society of Manufacturing Engineers

Key Words: Reverse Engineering, CAD, Modeling and manufacturing.

INTRODUCTION

Definition
"Reverse Engineering is the process of taking a finished product and reconstructing design data in a format from which new parts or molds can be produced."- The Society of Manufacturing Engineers.

Manufacturing Reality

Engineering is the profession involved in designing, manufacturing, constructing, and maintaining of products, systems, and structures. The effort to convert physical parts into virtual models is supported by a growing number of hardware and software. Efficiency gained in applying software and digitizing Equipment to automate the creation of virtual models is lost when the model cannot be used directly within CAD. If the virtual model cannot be manipulated within production CAD, the development process is hampered by a spiraling iteration of remote data capture, conversion and cleanup. A large time is invested to achieve a suitable production database for this issue. Reverse engineering has come a long way from the days when manufacturers used it to sidestep design and R&D processes and get to market by copying a competitor’s product. These gaps are often filled effectively by reverse engineering, which is one of the solutions for maintaining a system for a longer period of time. Today, reverse engineering is seen as the fastest way of translating the dimensions of a physical model or shape into the digital realm so that where manufacturing, machining, or repair plans can be written for it. In concept, it is fairly simple.

REVERSE ENGINEERING – CONCEPT INTRODUCTION

The process of duplicating an existing component, subassembly, or product, without the aid of drawings, documentation, or computer model is known as reverse engineering.
Reverse engineering can be viewed as the process of analyzing a system to: • Identify the system's components and their interrelationships • Create representation • one of the system in another form or a higher level of abstraction • Create the physical representation of that system
Define scope of work
General information is acquired for the customer and then key characteristics are identified.
Obtain dimensional data Utilizing dimensional lab’s metrology equipment and experienced personnel. It is possible to obtain all of the relative dimensional data necessary for the creation of an exact CAD replica of the component. If geometry is complex, digitizing or scanning may need to be employed Analyze data The dimensional data obtained is recorded, compiled and nominal values are formulated. Fit, function, manufacturing processes, industry standards and customer specifications are factored when setting the CAD models values.
Creation of the Cad Mode/Drawing A 3-D model is generated using customer compatible CAD packages. The defined nominal values are used and if digitized or scanned point clouds were necessary, a "best-fit" line, arc or spline is used to generate complex geometry or NURBS surfaces. Additionally "best practices" are utilized when creating models along with the customers' corporate standards when applicable. Some customers require 2-D drawings of the component. We obtain and use their CAD templates with title block information and any other corporate standards are used where necessary.

Ensuring Quality In addition to checking the dimensional data to the model/drawing, optional verification methods may be employed. Especially on parts containing complex, free flowing surfaces, that are difficult to fully capture on a CMM, and so "bestfit" methods are in the modeling .To verify the CAD surfaces the physical part can be partially or fully scanned using our scanning equipment. By comparing the point cloud data with the CAD model, a comparative analysis can be performed generating a report with a color map. The report highlights any deviations and there values from the referenced CAD model to the artifact. If any issues are identified the CAD model can be adjusted and the comparison repeated until even very complex surfaces are modeled accurately . Reverse engineering is essentially the development of the technical data necessary for the support of an existing production item developed in retrospect as applied to hardware systems. An object, such as a pump housing, plastic frame, boat hull, or aircraft nacelle is measured physically. Then the measurements are transcribed into a digital medium (a CAD-compatible platform) as an image of dots, streaming lines, or wire frames. Subsequently, this image can be enhanced for its end use via one or more software packages such as surfacing, stress analysis, human factors, ergonomics, plant layout, or product flow.

TRADITIONAL DESIGN PROCESS

REVERSE ENGINEERING PROCESS

Why reverse? For a new design, the dimensions of a mechanical model—from clay, plastic, wood, or wax—are copied digitally, and then embellished via surfacing, ergonomic, or other programs. For a product modification, reverse engineering is used to capture the existing mounting or mating structure as a drawing file (IGES-compatible format), and then manipulated in CAD or similar program to complete the adaptation. A good example of reverse engineering involves a sheet-metal fabricator that modifies military vehicles to carry external items, from auxiliary gasoline tanks to mounts for communications systems. They digitize the surface where a bracket is to be attached—including potential hole positions—and bring this image into their design software where it is used to shape the bracket. In repair applications, parts for which no drawings exist can be recreated by reverse engineering. This includes equipment that is old enough so that original drawings are lost, or that was built as a one-off time and never documented in the first place. For example, after years of service that included exposure to mild corrosion, a blade on an impeller for an air supply compressor cracked off. Ordering a new one from the manufacturer would take eight months. Plant engineers decided to reverse engineer a new one from the original. They measured the dimensions of the original to digitally capture the location of the blades, including the one that broke off. Shaft and bearing dimensions were also recorded. This data was downloaded into a CAM program and a machining plan was written to cut the new impeller. Actual milling was done in a machining center where the new impeller was cut from a blank of aluminum alloy that would have toughness and corrosion resistance that was at least equal to that of the original. From start to finish, the project took three weeks.

TRANSLATION TECHNOLOGY

If you can measure an object, you can reverse engineer it. The key is to be able to measure with sufficient accuracy to capture the degree of detail—in three dimensions—necessary for faithful reproduction. In the past, this was accomplished with some novel techniques, including one known as "stock building." As the name implies, a measurement from one point on an object was taken using calipers, rules, depth gages, etc. and a model was built with sticks, each stock representing an individual measurement. The accuracy of the model depended entirely on the skill of the model maker and the process usually required weeks to get it right. Eventually, measuring evolved to conventional CMMs, and now the object could be captured digitally. Accuracy was greatly improved. However, the process remained fairly slow because the CMM had to be programmed for each object so that the stylus on it could trace the physical part.
Two primary tools are employed for reverse engineering. For objects where the greatest dimension is 12 ft or less, an instrument that was originally developed for quality assurance departments to make fast, in-process quality checks is favored. Known as a portable CMM, it is based on an articulating arm, the joints of which are formed by optical encoders. They are able to reproduce the X-Y-Z location and I-J-K orientation of a stylus to an accuracy of ±0.001".
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1. Original wood model 2. Model scanned in polygon format using 3. Nurbs surface Proprietary 3-D scanning systems.

[pic] [pic] 4. Solid is created from Nurbs Nurbs surface has been interrogated for fidelity with the polygonized mesh and a color map generated

The arm moves freely within a sphere that is defined by its own reach. It captures data rapidly with the potential for hundreds of points being measured per minute. The arm records measurements as individual points or streaming lines in CAD-compatible software. For larger objects such as tool bedding or positioning, the digitizing is done with a laser measuring device that projects a laser beam to a moving target that can be positioned up to 100 ft away from the source.

COMPUTED TOMOGRAPHY IN REVERSE ENGINEERING

Reverse engineering of mechanical parts involves acquiring three-dimensional position data in the point cloud using laser scanners or computed tomography (CT). Representing geometry of the part in terms of surface points is the first step in creating parametric surface patches. A good polymesh is created from the point cloud using reverse engineering software. The cleaned-up polymesh, NURBS (Non-uniform rational B-spline) curves, or NURBS surfaces are exported to CAD packages for further refinement, analysis, and generation of cutter tool paths for CAM. Finally, the CAM produces the physical part. Today, the most important application of CT has become scanning for 3D-digitizing purposes. First of all, automotive and motorcycle industries as well as their suppliers and the medical technology show a very strong interest in the new possibilities that CT offers. Using this new technology it is possible to reduce the time to market for development of new products. Thus companies can realize substantial competitive advantages. Reverse Engineering is a term used to describe the creation of a digital dataset based on a physical representation, inverting the regular process of going from an idea through CAD construction to a product. There are several ways of digitizing a three dimensional object. Tactile and optical measurement systems require surfaces and geometrical features that are accessible or visible. However, CT can show internal structures as well. CT data can be processed directly in the form of point clouds or as tessellated surfaces (e.g. triangulated STL files). Segmentation of surfaces must take place in all. Computerized Tomography and Image Processing, three dimensions to avoid discontinuous changes in z-direction as it is the case in contour extraction done slice by slice. Transforming CT data into CAD systems with the tools available today is still a lot of work and therefore offers a big development potential. It is especially useful if CAD data of a product don't exist.
In future the rendering of a 3D-CAD dataset from 3D-tomograms for simulation and finite element analysis will be even more important. The reason why is the fact that the true object geometry instead of a theoretical model will serve as a base for computation. There are two parts to any reverse engineering application: scanning and data manipulation. Scanning, also called digitizing, is the process of gathering the requisite data from an object. Many different technologies are used to collect three-dimensional data. They range from mechanical and very slow, to radiation-based and highly automated. Each technology has its advantages and disadvantages, and their applications and specifications overlap. What eventually comes out of each of these data collection devices, however, is a description of the physical object in three-dimensional space called a point cloud.
Point cloud data typically define numerous points on the surface of the object in terms of x, y, and z coordinates. At each x, y, z coordinate in the data where there is a point, there is a surface coordinate of the original object. However, some scanners, such as those based on X-rays, can see inside an object. In that case, the point cloud also defines interior locations of the object, and may also describe its density.

REDUCING THE AMOUNT OF DATA

A CT scan produces a lot of data. The tomogram in our example had 946 slices with 1600 x 1000 pixels each. Every pixel was a four-byte floating-point density value. Hence the whole tomogram contained about 6 GB of data. To reduce the data two strategies were applied:
The water core was not the only surface to the given threshold value. Instead of generating a point cloud from all surfaces of the cylinder head and isolating the water core from this point cloud, it was better to perform a segmentation of the required surfaces. By extracting the appropriate region of interest, the data was reduced to about 1 GB.

A further strategy is to guess a threshold value, which is too low, and one, which is too high. Now only the pixels between these threshold values and their neighbours are stored using some run lengthencoding. This helps to compress the data without losing required information to compute the surface data. These methods should be applied before any further operations are performed. It saves not only disk space; it makes the following data handling easier and reduces time for data transmission to other computer systems. Therefore, a set of graphical tools was developed. With these tools the segmentation of the water core out of the 946 slices was done in about five hours.

POINT CLOUD GENERATION After performing the data reduction methods described above the point clouds of the upper and lower water core were generated using the 3D linear interpolation algorithm. With the transformations, which were determined from the positions of the reference bars, the two partial point clouds were fitted into a common coordinate system.
Once the digitized image is captured, users still need the right CAD software to speed up the reverse engineering process. Ideally, CAD software should be equipped to • Import geometric data of virtually any format • Work with point data, often on the order of several million data points • Work with contoured surfaces from creation through modification and analysis • Output geometry to downstream processes • Analyze geometry to evaluate form integrity with the sample. • Most important, the software should allow the user to visualize the part in a 3D perspective. A 3D model fully defines the shape of the part, eliminating the need for multiple view projection. Designers can rework surface contours, and toolmakers can then machine parts from the electronic mockups.
The idea is that the software should accelerate the reverse engineering time cycle by: • Improving the quality of surfaces by creating smooth, continuous curve networks • documentation • Eliminating the need for prototypes • Increasing product quality with a variety of analysis tools

REVERSE ENGINEERING IN AEROSPACE INDUSTRY The next major step for Boeing and other aerospace companies is a much higher level of integration for the design process and the parts used for new and aging airplanes. Reverse engineering holds the potential to provide a closed loop among CAD, CAM, CAE, hard tooling and inspection, making it much easier to exchange data. Even the seemingly simple process of measuring, modeling and verifying a physical part requires companies to look beyond traditional solid modeling systems to new reverse engineering technology that can capture the physical world and represent it with accurate, manufacturable digital models. Aerospace engineers view this step as an enormous challenge – the sheer scale of tracking millions of components can be conceptually and computationally overwhelming – but one that must be faced.It helps to take a deep breath and look back at the 100 years of aviation.

It's an amazingly compressed success story, from the early days of skepticism about the Wrights' initial flight, to the development of the Boeing 777.Aviation has progressed in leaps and bounds since 1903, pushing flight beyond the skies and into space. Over the next decade, sights will be set on the frontier traversed by reverse engineering: conquering the divide between the physical and digital worlds and creating full integration among all facets of the aerospace manufacturing process. In some situations, designers prefer to model in clay, plaster, wood of foam rubber, but a CAD model is needed in the further production process. Designing in CAD takes a long time and offers no guarantee that the models will be identical. Reverse engineering provides a solution to this problem because the physical model is the source of information for the CAD model.The physical model is placed on an instrument table and its contours are scanned layer by layer with a laser beam with an accuracy of up to 1µm. The Metris laser radars are the ideal inspection tools during manufacturing and assembly of aircraft and large component. The large measurement volume of up to 60 meter radius is a key benefit. Another important advantage is the fact that there are no operators necessary to hold reflectors, position photogrammetric dots or handle touch probes, benefits that impose the laser radar as a real non-contact inspection solution. CMM based 3D laser scanners are mainly used in companies that supply smaller components for aerospace or energy industry.

One of the typical applications is the inspection and reverse engineering of turbine blades and airfoils. The reverse engineering application is often used in aerospace design departments to speed up the design and prototyping stage.
OTHER INTRESTING APPLICATIONS OF R.E. • Medical specialists use 3D digitizers to digitize bones and other anatomy for the development of prosthetics and implants.(practically used in CMC Vellore) • Video production experts use them to capture difficult to create shapes for TV commercials and special effects in Hollywood films. • Reverse engineering is today a key application in design departments to obtain an accurate CAD surface model from clay models.

• Reverse engineering successfully used in ORDNANCE FACTORIES. Indian defense has now found this technology as an easy way of upgrading its armed forces with new world class weapons.
( 12.7/14.5/20 mm ANTI MATERIAL RIFLE ) ( (VIDHWANSAK) SOUTH AFRICAN MODEL ( INDIAN MODEL

• Reverse engineering used in sculpture design and foaming, first the scanning was done using a laser scanner on a 12 foot CMM arm. Over 6 million data points were acquired and the scanning technicians were not permitted to physically touch the statues during the scanning process then the pattern was then cut at full size with a 5-axis CNC router.

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• Reverse engineering in dentistry for making the exact replica of the matching teeth with correct alignment.

• Reverse engineering was used to restore the original fossil since the original skelton was found with many bones missing, archiving the bones for replication, and replacing missing or damaged parts with CNC Milling or Rapid Prototyping techniques.

Bones of the de-mounted Reverse engineered triceratops Triceratops being restored

Advantages of Reverse engineering

• Fast availability of CAD models • Physical model is used as the starting point • Shortened development process • Fully developed product at the start of production • Reduction in product and production costs • The development of CAD models based on physical ones • Editing a CAD file using the altered physical model creating STL files for use in other Rapid Prototyping techniques

CONCLUSION Many American engineering colleges have courses in reverse engineering to focus on redesign, instead of original design, as a problem solving approach. Even the automobile industry uses a variant design methodology, referred to as direct engineering, to replace more general original design methods. In recent years, Americans and Europeans have reverse engineered the reversed engineering process and developed powerful tools to further compress development cycles. Such tools are relevant for industries in those countries where production engineers are faced with the problem of reproducing parts directly from samples. Making spares for obsolete equipment, fabricating copies of old tooling, or redesigning a foreign-licensed product to come up with a new look are examples of how reverse engineering can be successfully employed.

REFERENCES: 1. Kathryn A. Ingle, Reverse Engineering Mc Graw Hill Inc. 2. Kevin Otto & Kristin Wood, “Product Design Techniques in Reverse Engineering and New Product Development”, Pearson Education 3. International Symposium on Computerized Tomography for Industrial Applications and Image Processing in Radiology, Industrial Computed Tomography in Reverse Engineering Applications March, 15 - 17, 1999 Berlin, Germany 4. www.rsleads.com/404tp-170

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Need

Design Idea

Prototype & Test

Product

REVERSE ENGINEERING PROCESS

Design Recovery

Measure & Test

Disassembly

Product

RE Product

Fig 2: Point cloud of water core

Fig 3: Visualization of water core

Reverse engineered human knee