The document discusses the process of reverse engineering, including defining reverse engineering, its major steps, and applications. Reverse engineering involves scanning a physical product to create a digital CAD model without design documents. It has several purposes like redesigning components, reproducing obsolete products, or shortening development times. The key steps are scanning to capture point cloud data, processing points to reduce noise, and developing geometric models from the point data. Examples of reverse engineering various common products are also provided.

1. Chapter 3
Reverse Engineering

2. Definition: Reverse Engineering
 Reverse engineering is opposite to forward engineering.
 Works with existing product to create CAD model and modify or reproduce
the design aspect of the product.
 Can also be defined as duplicating an existing product by capturing its
physical dimensions.
 Reverse engineering is also defined as the process of obtaining a geometric
CAD model from 3-D points acquired by scanning/digitizing existing
parts/products.
 Reverse engineering helps in redesigning a component for better
maintainability and also to reproduce a system without access to its design
documents.

3. Introduction
 Companies are exploring
ways to reduce lead times for
new product development.
 Reverse engineering is now
considered among the
technologies that provide
business benefits in
shortening the product
development cycle.
 Reverse engineering allows
the possibilities of closing
the loop between what is
“designed” and “ actually
manufactured”.

4. What is Reverse Engineering ?
Engineering is the process of designing, manufacturing,
assembling and maintaining products &
systems.
 Forward engineering : is the traditional process of moving
from logical designs to the manufactured and assembled
systems. In some situations, may be product are available
without any technical details e.g. drawing, bills of material
or without engineering data.
 Reverse engineering : process of duplicating an existing
part, subassembly, or product, without drawings,
documentation is known as reverse engineering.

5. Reverse Engineering a Solution
 As products become more organic in shape designing in CAD
becomes more challenging without any guarantee that the CAD
design will replicate the sculpted model exactly.
 Reverse engineering can be considered as an optimal solution to
the above problem.
 The physical model is the source of information for the CAD in
the reverse engineering.
 Reverse engineering also helps in compressing the product
development lead time.

6.  The process is also referred as physical to digital process.
 Example: injection molding companies explore ways to reduce the design
development time of tool and die.
 Reverse engineering helps in transferring a physical product or clay mock
up in digital form. Digital form can be easily remodeled and exported for
rapid prototyping or rapid manufacturing.

7. Why Use Reverse Engineering ?
 The original manufacturer no longer exists, but a customer
needs the product, e.g. , aircraft spares required typically after
an aircraft has been in service for several years.
 The original manufacturer of a product no longer produces the
product, e.g. , the original product has become obsolete.
 The original product design documentation has been lost or
never existed.
 Creating data to refurbish or manufacture a part for which there
are no CAD data, or for which the data have become obsolete or
lost.
 Inspection and/or Quality Control–Comparing a fabricated part
to its CAD description or to a standard item.

8. Cont……
 Some bad features of a product need to be eliminated e.g. ,
excessive wear might indicate where a product should be
improved.
 Strengthening the good features of a product based on long-term
usage.
 Analyzing the good and bad features of competitors’ products.
 Exploring new avenues to improve product performance and
features.
 Creating 3-D data from a model or sculpture for animation in
games and movies.

9. Cont……
 Creating 3-D data from an individual, model or sculpture to
create, scale, or reproduce artwork.
 Architectural and construction documentation and
measurement.
 Fitting clothing or footwear to individuals and determining the
anthropometry of a population.
 Generating data to create dental or surgical prosthetics, tissue
engineered body parts, or for surgical planning.
 Documentation and reproduction.

10. Reverse Engineering Strategy
 Reason for reverse engineering a part
 Number of parts to be scanned–single or multiple
 Part size–large or small
 Part complexity–simple or complex
 Part material–hard or soft
 Part finish–shiny or dull
 Part geometry–organic or prismatic and internal or external
 Accuracy required–linear or volumetric

11. Majors Steps in R.E.

12. Reverse Engineering: The Generic
Process
R.E. is a 3 phase process
i. Scanning
i. Point processing
i. Application specific geometric
model development

13. Scanning Phase
 Selection of correct scanner.
 Preparing the part to be scanned.
 Scanning to capture geometric details e.g. steps, slots, pockets
and holes.
 3D scanners for scanning part geometry, producing clouds of
points to define surface profile.
 Two types of scanners.
i. Contact
ii. Non-contact

14. Data Acquisition Techniques

15. Contact Scanner
 Contact probes automatically follow
contours of a physical surface.
 Probe devices are based on CMM
technologies, tolerance range 0.01-0.02mm
 Speed of scanning is function of size of
part, generally slow for large parts.
 Tactile device probes must deflect to
register a point, a degree of contact
pressure is required.
 Restrictions with contact pressure limits
the use of this technology for soft
materials.

16. Non Contact Scanners
 Based on lasers, optics and charge couple
devise sensors.
 Tolerance limit in the range of ± 0.025 to
0.2mm.
 Problem in scanning surface parallel to axis of
laser.
 Shiny surfaces needs to be treated with fine
powder before scanning.
 Employed when the accuracy of the
information generated is secondary to the
speed.
 Output of scanning phase id point cloud data.

17. Laser Triangulation
 Location & angles between light
source & photo sensing devices to
configure position coordinates.
 Light is focused at a predefined
angle on the surface.
 Photosensitive device captures the
reflected light & using geometric
triangulation the coordinates of
surface is recorded.
 Light source and photosensitive
device is normally mounted on
moving platform to enable multiple
scans.
 Accuracy of scan depends on the
resolution of the photosensitive
device & the distance between the
surface & scanner.

18. Interferometry
 Measure the coordinates of any
point/ feature in terms of
wavelengths using interference
patterns.
 Considered as very accurate, since
light has a wavelength in the order
of nanometers, while R.E.
applications are in the range of cm
to m.
 Generally, a monochromatic beam
of light is employed both to probe
the object and for a reference
beam for comparing with the
reflected light.

19. Structured Lighting
 A popular method is shadow
Moire, where an interference
pattern is projected onto a surface
producing lighted contour lines.
 These contour lines are captured
in an image and is analyzed to
determine the distances between
the lines.
 Distance between interference
lines is proportional to the height
of the surface at the point of
interest & coordinates of surface
points can be deduced.

20. Stereo Image Analysis
 Relative locations of landmarks in multiple images are related to
position coordinates of points of interest.
 Method is similar structured lighting method.
 Image frames are analyzed to determine coordinate data.
 Analysis does not rely on projected patterns, but, stereo pairs are used
to infer information to determine coordinates.
 Referred as passive method, as no structured light is employed.
 Correlation of image pairs & landmarks with the help of images is
considered as a complex procedure hence active methods have
preference.

21. Other Methods
ACOUSTIC
 Sound is reflected from a surface.
 Essentially the same as time of flight
 Distance between surface & source is measured with known speed of
sound.
MAGNETIC FIELD
 Involves sensing the strength of magnetic field source.
 Magnetic touch probes are employed of sensing the location and
orientation of a stylus within the field.
HYBRID
 Combination of contact & non-contact systems.

22. Non Contact Scanners: Advantages
 No physical contact.
 Fast digitizing of substantial volumes.
 Good accuracy and resolution for common applications.
 Ability to detect colors.
 Ability to scan highly detailed objects, where mechanical
touch probes may be too large to accomplish the task.

23. Non-Contact Scanning : Challenges
 Calibration
 Accuracy
 Accessibility
 Occlusion
 Fixture (placement)
 Multiple views
 Noise and incomplete data
 Statistical distributions of parts
 Surface finish

24. Point Processing Phase
 Importing the point cloud data,
reducing the noise in the
collected data & also reducing #
of points.
 Tasks were performed using a
range of filters.
 Also allows to merge multiple
scan data sets.
 Good datum planning for
multiple scanning will reduce
the effort required in the point
processing and avoid errors
from merging multiple scan
data.
 Output is a clean, merged point
cloud data set.

25. Application Geometric Model
Development Phase
 Generation of CAD models from
point data is probably the most
complex activity.
 Surface fitting algorithms are
required to create surface to
represent 3D information
described within the point
cloud data set.
 Most CAD systems are not
capable to display and process
large amount of point data, as a
result discrete software
packages are required for point
processing.
Point cloud Triangulated surface

26. Steps for Multiple Overlapping
Scan

27. Is Project Suitable for R.E. ?
 How will the team perform the investigation?
 What constraints have to be dealt with in analyzing the artifact?
 What plan will best unravel the artifact’s function and design
features?
 What types of plots or graphical displays will best communicate
discoveries about the object’s function?
 How was it manufactured?
 What is the consumer population?
 Are design improvements possible?
 What kind of an ad or commercial will be suited for the object?

28. Reverse Engineering: Applications
 Frisbee
 Aluminum can
 Wind-up toy robot
 Disposable camera
 Stapler
 Climbing rope
 Coffee maker
 Thermos
 Ski binding
 Water gun
 Lighter
 Match
 Bicycle light system
 Audio speakers
 Shock absorber

29. Aluminum Can : Procedure
i. Measured dimensions
ii. weight
iii. flow
iv. rates (wide mouth, narrow mouth),
v. force (required to open)
vi. load (to deform and to explode).
vii. The deformation force defines the critical axial buckling load.

30. Aluminum Can : Results/Conclusion
 Requires 550 to 600 pounds to deform.
 Requires 725 to 790 pounds to explode.
 Wide mouth takes 8.3 seconds to empty.
 Narrow mouth takes 13.6 seconds to empty.
 Ease of recycling is a big advantage.
 617 cans can be stacked high without damaging the bottom
can. This is important for storage and shipping.

31. The Match : Procedure
i. Studied history.
i. Measured the burn time of matches of different lengths as a
function of angle.
i. The critical angle to hold a match in the wind (a fan was
used).
i. The striking force and match angle (an air track was used).

32. The Match : Results/Conclusion
 Held horizontally, a short match burned about 1.7 inches in 30
seconds.
 Held at 45°, a short match burned about 1.4 inches in 12
seconds.
 In wind, it is best to point a match straight down.
 The best striking angle was between 35 - 40° from the surface.

33. The Toaster : Procedure
i. Dissected object.
i. measured dimensions.
i. Measured temperature and time at each setting.
i. Measured electrical resistance.

34. The Toaster : Results/Conclusion
 The time for toasting ranges with settings from 20 to
34 seconds, if the toaster is cooled between tests.
 The time for toasting ranges with settings from 4.7
to 11.7 seconds, if the toaster is not cooled between
tests. Hence, for a quick response, let the toaster go
through a heat cycle before initially toasting.
 The toast compartments taper in width from top to
bottom. The team theorized that this permits
smaller, thicker items to be toasted without falling to
the bottom of the toaster.

35. R.E. : Project Report
Background:
Describe what need the device fulfills. Give a brief history of the
design. Include any accompanying literature as an appendix.
Project Goals:
List the goals for performing the reverse-engineering study; i.e.,
what will be learned from the study?
Test and Analysis Procedures:
Describe the procedures used to address the above goals. How was
the device and its components evaluated? Document test data
obtained.

36. Dissection Details:
Describe (using drawings, photos and/or video where appropriate)
the key components and how they function.
Results:
Describe what was learned about this device’s design and
functionality. Provide suggestions for changes that would improve its
function or make it more cost effective to produce. Provide
suggestions for any changes that would make it “greener” or more
universally available.
Marketing:
Include either an advertisement (in print) or a video or radio
commercial, marketing this artifact to an identified target group of
potential customers.