ADDITIVE MANUFACTURING

1. UNIT - 2
REVERSE ENGINEERING

2. Basic concept
• Reverse Engineering (RE) is the process of
generating a Computer Aided Design
(CAD)model from an existing physical part.
• It enables the reconstruction of an object by
capturing the component's physical
dimensions and geometrical features .
• The main aim of reverse engineering is to
reduce manufacturing costs of the new
product, making it competitive in market.

3. Need for Reverse Engineering
• Manufacture of service components after
discontinuation of the product line.
• Redesign of an existing design which lacks
adequate product data documentation.
• Corrupt data file or loss of CAD design for a
product.
• Generation of cheaper alternate products as a
substitute for monopoly products.

4. Digitizing
• Collecting data from physical part.
• Used when drawing of object is not available.
• Aim is to generate a 3D mapping of the
product in the form of CAD file.
• This requires acquisition of surface data,
which is large number of points on the product
surface.
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5. Digitization techniques
Non-contact reverse engineering digitization
Techniques
Contact reverse engineering digitization
Techniques

6. Digitization techniques
Contact method
• Requires contact between
the component surface & a
measuring tool.
• Uses Coordinate Measuring
Machine (CMM),
electromagnetic digitizer or
sonic digitizers to get
desired coordinates.
Non contact method
• Uses light as the main tool
• Uses white light or laser
scanners to scan 3D objects
to generate CAD design.
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7. REVERSE ENGINEERING

8. CONTACT BASED
• Contact based methods of reverse engineering
have been available for nearly 40 years.
• The first method of reverse engineering to be
introduced was the coordinate measuring
machine (CMM)
• A CMM gives physical representation of a three
dimensional Cartesian coordinate system

13. Types of CMM Configurations
1. Cantilever Type
2. Bridge Type
3. Column Type
4. Gantry Type
5. Horizontal Arm Type

14. Cantilever Type

15. Bridge Type

16. Column Type

17. Gantry Type

18. Horizontal Type

21. Noncontact Inspection Techniques
Uses a sensor or probe located a certain distance
away from the object being measured or gaged
• Two categories:
Optical – uses light to accomplish the inspection
Non-optical - uses energy form other than light
• Advantages of noncontact inspection:
Avoids possible damage to surface of object
Inherently faster than contact inspection
Can often be accomplished in production without
additional part handling
Increased opportunity for 100% inspection

22. Optical Inspection Method- Machine Vision
• It is the creation of image and the collection of data derived
from the image and subsequent processing and interpretation
od data by a computer from useful application.
• It is also known as computer vision
• Machine vision exists in 2D & 3D format with 2D being most
common in industrial application.
• Machine vision has 3 functions:
 Image acquisition and digitization
 Image processing and analysis
 Interpretation

23. Optical Inspection Method- Machine Vision

24. • Image acquisition and digitization
 It is performed by deploying a video camera to capture the image and
use digitizing system to store image data for subsequent analysis.
 The camera is focused upon surface of item of interest and image
consists of discrete pixel elements is captured by viewing area.
 Each pixel value has value proportional to light intensity of portion of
scene.
 The intensity value of each pixel is converted into digital value by
analog to digital converter.

25. • Image processing and analysis
 A number of technique have been developed so that data
produced during first phase of machine vision may be processed.
 General techniques are called segmentation and feature
extraction

26. • Interpretation
 Interpretation of the image is concerned with recognizing
the object recognition, and/or pattern recognition.
 Two commonly-used interpretation techniques are
Template matching:- a method whereby the features of
the image are compared against corresponding features of a
model or template stored in the computer memory
Feature weighting:- technique in which several features
are combined into a single measure by assigning a weight to
each feature according to its relative importance in identifying
the object, and where the resultant score is compared against
an ideal object score stored in computer memory, to achieve
proper identification

27. Non Contact Inspection method

28. Additive Manufacturing Technology

30. 3D SCANNING
• 3D scanners are tri-dimensional measurement devices used to
capture real-world objects or environments so that they can be
remodelled or analysed in the digital world.
• The latest generation of 3D scanners do not require contact with the
physical object being captured.
REAL OBJECT 3D MODEL

31. Objects are usually Scanned in 3D for 2 Purpose
1. Extracting dimensions to reconstruct a CAD reference file for
reverse engineering or rapid prototyping.
2. Measuring the object itself for analysis and documentation.
It is done in application such as computer-aided inspection,
digital archiving and computer-aided engineering analysis.

32. Two Categories of Scanners
• White light and structured light systems
• Scan arm and portable handheld scanners

33. How 3D Scanning Works
• Scanning results are represented using free-form, unstructured
three-dimensional data, usually in the form of a point cloud or
a triangle mesh. Certain types of scanners also acquire color
information for applications where this is important.
• Images/scans are brought into a common reference system,
where data is merged into a complete model. This process --
called alignment or registration -- can be performed during the
scan itself or as a post-processing step.
• Computer software can be used to clean up scan data, filling
holes, correcting errors and improving data quality. The
resulting triangle mesh is typically exported as an STL FILE or
converted to NURBS surface for CAD modelling.