Mr. BHUT SHAILESH G. Mr. RANA PRAVIN P

Reverse Engineering

A

Paper On

“REVERSE ENGINEERING”

Submitted By:

Mr. BHUT SHAILESH G. Mr. RANA PRAVIN P.

(E-MAIL:) (E-MAIL:)

(MOB.: +91-9923240980) (MOB.: +91-9423952940)

T.E. [ MECH.]

DEPARTMENT OF MECHANICAL ENGG.

R. C. Patel Institute of Technology

Shirpur – 425405.

[2009]

ABSTRACT

Reverse engineering (RE) is the process of discovering the technological principles of a device, object or system through analysis of its structure, function and operation. It often involves taking something (e.g., a mechanical device, electronic component, or software program) apart and analyzing its workings in detail to be used in maintenance, or to try to make a new device or program that does the same thing without copying anything from the original. The resulting device has low-cost, ease of manufacturing and more functions along with removing drawbacks of earlier system.

Reverse engineering often is done because the documentation of a particular device has been lost (or was never written),Product analysis,Security auditing, Competitive technical intelligence,Do not make the same mistakes that others have already made and subsequently corrected,Curiosity, interoperability, learning purposes,Removal of copy protection, circumvention of access restrictionsetc.

This paper explores the basic concept of reverse engineering. Its process and future based reverse engineering with example.

KEY WORDS: Definition, need, reverse engineering process for mechanical part,future based reverse engineering with example, digitizer, CMM.

INDEX

1. INTRODUCTION………………………………………………………… 3

1. WHEN IS IT TO BE IMPLIMENTED? ………………………………… . 3

1. PROSSES FOR MECHANICAL PART………………………………….. 4

1. FUTURE BASED REVERSE ENGINEERING………………………….. 4

1. EXAMPLES………………………………………………………………. 5

1. DIGITIZER………………………………………………………………... 8

1. CMM………………………………………………………………………. 9

1. CONCLUSION…………………………………………………………… 11

1. REFERANCES…………………………………………………………… 12

INTRODUCTION - REVERSE ENGINEERING

• 1.1 What is Reverse Engineering?

“Reverse engineering is the process in which a manufactured part is measured without the benefit of a blueprint for dimensional reference. The results are then reviewed, refined, and the part is re-manufactured.” Reverse engineering is taking apart an object to see how it works in order to duplicate or enhance the object. In the automobile industry, for example, a manufacturer may purchase a competitor's vehicle, disassemble it, and examine the welds, seals, and other components of the vehicle for the purpose of enhancing their vehicles with similar components. It's a practice taken from older industries that is now frequently used on computer hardware and software.

1.2 When Reverse Engineering is to be implemented?

You may need to reverse engineer a component when,

• Repair and maintenance facilities require replacement parts with diminishing sources of supply.
• Original equipment manufacturers (OEMs) are either unwilling or unable to supply replacement parts, or demand inflated costs for sole-source parts. Reverse engineering allows for the competitive procurement of such parts.
• Technical Data Packages (TDPs) initially created by the OEM are inadequate, or proprietary and unavailable. TDPs for the required parts may have been misplaced or may no longer be in existence.
• It is advantageous to update obsolete materials or antiquated manufacturing processes with more current, less expensive technologies.
• Competitive advantage may be gained through reverse engineering analysis for the purpose of producing and selling a similar product.

• 1.3 Reverse Engineering process for mechanical part

After a decision has been made to reverse engineer, the following steps should be completed before continuing with the process.

(a) Preliminary Steps

(b) Identify components

(c) Determine the design intent

(d) Create management plan

1.4 Feature-Based Reverse Engineering

To demonstrate the effectiveness of feature-based reverse engineering, we have created a prototype system called REFAB (ReverseEngineering – FeAture-Based). REFAB allows a user to interactively define a model composed of mechanical features from a set

of intensity images, registered to range images. The user specifies the types of manufacturing features present and the approximate location of each feature in the object. REFAB deals with the determination of precise, quantitative parameterization of each feature. The final output is a fully specified model usable by the Alpha 1 CAD/CAM system. Figure 2 shows the user interface for the REFAB system. The series of small images along the top corresponds to alternate views of the same object and allows the user to specify a current working view. The set of buttons at the lower left corresponds to the set of features the system is able to model. To model a feature, the user selects a feature type and a view in which the feature can be seen on the object. The panel on the lower right will show the selected view and all previously modeled features. The mouse is used to specify enough points on the displayed image to indicate the approximate location of the feature. REFAB will then analyze the range data to provide an optimal parameterization of the feature, render the feature on the display, and then prompt for the next feature to be modeled. While a fully automated system might seem desirable, there are two aspects of modeling for manufacturing that cannot be done based on automatic processing of sensed data alone.

The REFAB system acknowledges the need for human intervention, but frees the user from most of the tedious, quantitative analysis that can be done faster, easier, and more accurately by automated tools. The current version of REFAB is limited to five common types of features: stocks, simple holes, profile pockets, profile islands, and profile sides. Each of these is an extrusion of a planar curve, a property which can be exploited to improve accuracy when fitting to sensed data.

1.5 Examples - REFAB

The object is part of the vehicle’s steering arm assembly and is approximately 4"x 2"x 3/4" (Figures 9 and 10). Figure 9 is included for information only. All reverse engineering operations were done without using any aspect of the CAD models from which the parts were originally constructed. Testing REFAB on objects of known geometry and design allows a comparison of the recovered model with the true shape of the part. Parts were painted to remove specularities that cause problems for most current range finding systems. Multiple views were taken of each part and registered into common point-cloud data sets, using the.

Figure 11 show 10% samplings of both point sets, rendered so that nearer points are brighter. 12,804 were used for the steering arm. Figure 12 is wire frame drawing generated from the reverse engineered CAD models produced by REFAB for the two parts. To emphasize that the recovered CAD models are feature-based and not just arbitrary surface representations, Figure 15 show exploded view of the two models indicating the separate features making up each object. The steering arm has an outer profile side with both smooth contours and sharp corners, one large hole and one smaller hole drilled normal to the stock, and two small holes drilled in a perpendicular orientation. Figure 16 show rendered views generated from the reverse engineered CAD models.

SCANNER FOR REVERSE ENGINEER A MECHANICAL PART . ( DIGITIZER AND CMM )

2.1 Digitizer

For the purpose of generating a CAD model of complicated shape digitizer is used. It is similar to that of one conventional scanner. Figure 17 shows the one type of digitizer, manufactured by the company named DIGIBOTICS.

Figure 17: Digitizer from DIGIBOTICS

Reverse engineering of mechanical parts using automatically acquired three-dimensional position data has for the most part used rather unsophisticated geometric models. Often, a digitizer is moved along parallel scanning paths and NC code generated to move a cutter along the same 3–D path. In effect, no model other than the raw scan data is used, though preprocessing to remove noisy data points, align scan lines from multiple scans, etc., is usually necessary. Alternately, a triangulated mesh or NURBS surface is created from the raw data points and tool paths generated to move a cutter over this surface.

High performance 3-D input systems combining advanced laser ranging technologyand personal computing. Using automatic four-axis adaptive scanning capabilities. System providesfast, simple, and accurate way to copy or inspect complex surfaces. By intelligently measuring sequential points along cross-sectional contours, data is highly organized, complete and directly interfaces to any CAD/CAM/CAE, imaging, or animation software that reads 3-D points, polylines, or a polygonal mesh. This systems is used in a wide range of industrial and academic applications involving 3-D design, inspection, replication, analysis, visualization, and animation.

3D Laser Digitizing Systems include control and data editing software for operation on a standard personal computer. Automatic scanning capability, high reliability and up-time, and ease of operation result in exceptionally low cost of operation.

These systems are ideal for office and laboratory environments, require no facilitation or special environmental controls other than being shielded from incandescent lighting and direct sunlight, and there are no consumables. System using a small amount of floor space.

2.2 CMM (Coordinate Measuring Machine)

Most CMMs are five axis robots, capable of moving in 3–D Cartesian space as well as providing roll and pitch rotation. They acquire data by physical contact of the probe with points on surfaces of interest. Very high positional accuracy is possible, but sensing of a large number of points is extremely slow and expensive damage can be done if the probe is not maneuvered towards the object along an appropriate path.

Coordinate Measuring Machines are available in manual, manual/joystick, and full computer control. These machines play a valuable role in precision measuring because the surface plate, height gage and indicator inspection procedures provide a fast, accurate and more convenient alternative to conventional methods for measuring complex parts. A Coordinate Measuring Machine system is composed of a base machine and a software package, aided by many probe options and accessories. To take full advantage of these measuring systems, the machine must be stable and accurate, and the software package must be easy to use, flexible, and powerful. Conventional CMM is shown in figure 18.

Figure 18: Coordinate Measuring Machine (CMM)

3. Reverse Engineering- Using 3D Laser Scanning

Technology today gives us the ability to use a non-contact 3D laser scanner to capture large amounts of data. That data can now be manipulated via software to produce a 3D parametric model

/ The process starts with a digitalscan. Usually consisting of several scans combined to make one closedpolygon mesh.
/ In this examplea plane can be applied to the flat of each flange. CAD tools are used to pick pointson the scan surface. The mathmatical mean is calculated and the plane is created that best fits the data points selected.
/ Circles are then created from the point cloud data on the planes; the vector data is then extruded into a solid cylinder representing the flange.
/ The CAD process ofconvertingpoint clouddata into vector data is continued. The CAD data is then extruded into a solid model feature.
/ When all of the features from the scan have been converted into solid model features you have created a complete parametric model. A model like this one can be exported directly into SolidWorks and revised or edited.

CONCLUSION

Reverse engineering a part or assembly can provide an improved or added performance to an old process. New and improved materials and techniques may be utilized improving operations, maintenance and support.

REFAB is able to create CAD models based on position data, where the precision of the position information is far less than usually used in reverse engineering applications. This success comes about because segmentation and fitting is done with manufacturing-specific geometric models. These models effectively reduce the uncertainties in the sensed data by exploiting constraints implicit in each feature type. Future experiments will be conducted using higher precision sensors, with the goal of ultimately being able to reproduce machined parts to a tolerance typical of current NC machining practice.

In manufacturing 3-D digitization allows for a form of reverse CAD in which CAD models are created from existing parts, rather than creating the CAD models on a design system and then using the models to fabricate a part.

Part-to-CAD reverse engineering allows up to date NC fabrication plus easier modification of the design.