Unit 1 - Basics of Design

1. UNIT I BASICS OF DESIGN
CME340 – CAD/CAM
Mr.M.Mani
AP-MECH

2. UNIT I - BASICS OF DESIGNS
Understanding of Projections, Scales, units, GD & T; its 14
symbols, Special characteristics & Title Block readings. Revision /
ECN status of drawings Customer Specific requirements Drawing
Grid reading
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3. Course Outcomes
• At the end of the course the students would be able to
• Discuss the basics of the design and concepts.
• Develop the two dimensional drafting and projection views.
• Discuss the three dimensional modeling, parametric and Non-
parametric modeling
• Discuss the assembly modeling and top down, bottom up
approaches.
• Develop the computer aided machining and wirting part
programming.
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4. An engineering drawing
• An engineering drawing is a type of technical drawing that is
used to convey information about an object. A common use
is to specify the geometry necessary for the construction of a
component and is called a detail drawing. Usually, a number
of drawings are necessary to completely specify even a
simple component.
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5. Types
• part drawing and
• assembly drawing
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6. Sample drawing
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7. Projections Methods in CAD Drafting
• Drafting is also spelled as draughting, is popularly known as an
engineering drawing. Drafting is the process of representing an object
or idea through lines having various thicknesses and make ups.
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8. Classification of Drafting:
• Based on the usage of drafting
• Furniture drafting
• Architectural drafting
• Mechanical or machine drafting
• Electrical and electronics drafting
• Structural drafting and sheet-metal drafting, etc.,
• Based on the function of drafting
• Manual drafting
• Computer-Aided Drafting or Designing (CAD)
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9. Advantages of Manual Drafting:
• Low Cost of Drafting Equipment: Manual drafting is created by using
drafting equipment like a Pencil, Scale, Mini-Drafter, Compass, etc. The cost
of drafting equipment is less compared to CAD Software Packages.
• No Cutting End Technology Required: Unlike CAD Systems, you don’t need
to maintain the systems with expensive maintenance services. Maintaining
the Pencil and Paper is easy to do.
• No Need for Subscriptions: In the manual drafting we are not going to use
CAD software. If we use CAD software, we need a subscription for the
same. It will improve the cost involved in the process.
• No training required: Apart from the training which we get while studying,
there is no need for the designers to teach the CAD packages being used.
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10. Advantages of CAD drafting:
• Quality of Design: The CAD software has different tools to create drawings accurately
as per the requirement. The quality of the CAD is better compared to Manual
drafting.
• Easy for Documentation: For manual drafting, we have to maintain a lot of
documents. Handling and maintaining the document is a very difficult process in
manual drafting. But, in CAD drafting, saving and sharing the documents is very easy.
Documents can be saved in the local storage or in the cloud storage.
• Modify and Reproduce Faster: Modifying the existing drawing and reproducing the
drawing is very easy in CAD drafting. It is very complicated in the Manual drafting
process.
• Ability to Create a Drawing from 3D Models: In CAD drafting you can directly import
any 3D CAD model you can create different views like Front, Side & Top, etc. in CAD
drafting.
• Following the Standards: Different standards are available in CAD drafting. Based on
the standard which you are selecting the views and annotations are automatically
added. But, In Manual drafting, you have to know about all the standards. Only then
you can create proper drafting.
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11. Use of Projections in Drafting:
• Projection is used to represent the Complex 3D object in the 2D
drawing sheet.
• Projection is used to show the Shape and Size of the object in the
Drawing or Drafting sheet.
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12. Definition of Projections:
• As an object, it has three dimensions length, width and height. The
shapes and size of the object to be represented on a sheet, which has
only a two-dimensional plane.
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16. scale
• A scale is defined as the ratio of the linear dimensions of the object as
represented in a drawing to the actual dimensions of the same.
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18. •
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20. Plain Scale
• If a line divided into number of equal parts; the first part is
further sub divided into small parts. It represents either two
units or a unit and its fraction such as km and hm
• 1 decimeters (dm) = 10 cm
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24. Diagonal Scle
• Diagonal scales are used either to measure very minute
distance such as 0.1mm or to measure three units such as dm ,
cm and mm
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31. Drawing units
• When drawing using a CAD software we always draw "real" size (i.e.
the scale is 1:1 in the computer space). For example if we draw a box
with size 20x20x20 cm we will use 20 drawing units for drawing the
sides.
• Independently of the scale that we will use to print the drawing we
will not scale when we draw on the CAD software. This is a major
benefit of CAD software! Nobody wants to hold a calculator the
whole time and scale while drawing! Drawing in one thing, scaling for
printing is a totally different thing.
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32. Drawing units
• We set the scale only at the printing layout which is prepare at a
later stage when the drawing is completed and we are ready for
printing. In all CAD software, the printing layouts are always a
distinct part of the software that helps us fit the drawing to the
paper. In all CAD software, drawing is one thing and printing is
another thing.
• Before we start drawing we decide in our mind what will be the
value of a unit length in the drawing. One drawing unit can be
equal to one meter, one mm, one cm, one kilometer (km).
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33. Drawing units
• It is up to us to decide what the units will be depending on the
size actual size of our structure or object. For example, if we
draw a coin with a diameter of 20 mm it is convenient to use
mm (millimeters). Thus we will draw the coin using a circle with
a diameter of 20 units. In this case, one drawing unit represents
1 mm.
• If we draw the structural drawings for a concrete house it is
much more convenient to use meters (m). In that case one
drawing unit represents 1 m. Then a square house with layout
of 20x20 meter will be drawn using a square with side-length of
20 drawing units.
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49. Special characteristics
• In CAD (Computer-Aided Design) design, there are several special characteristics
or features that can enhance the functionality, aesthetics, or manufacturing of a
product.
• Here are some commonly used special characteristics in CAD design:
• Fillets and Chamfers: These features are used to round or bevel the edges or
corners of a part, reducing stress concentration and improving aesthetics.
• Draft: Draft is a taper applied to vertical walls of a part to aid in its easy release
from a mold during manufacturing.
• Threads: CAD allows the inclusion of threads, both internal and external, which
are essential for fasteners and threaded connections.
• Ribs and Bosses: Ribs are thin, structural elements added to strengthen a part,
while bosses are protruding features used for mounting or fastening purposes.
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50. Special characteristics
• Holes and Cutouts: CAD designs can include accurately placed holes,
slots, or cutouts for various purposes such as assembly, ventilation, or
access points.
• Embossing and Engraving: These features involve adding raised or
recessed text, logos, or patterns to a part's surface for branding or
aesthetic purposes.
• Patterns and Symmetry: CAD allows for the creation of patterned
features or symmetric elements, which can improve efficiency, aesthetics,
or functionality.
• Snap Fits and Interlocking Features: These features enable parts to be
assembled or connected without the need for additional fasteners or
adhesives
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51. Special characteristics
• Tolerance and Clearance: CAD design includes specifying tolerance
levels and clearances to ensure proper fit, function, and assembly of
parts.
• Assembly Constraints: CAD software provides tools to define
constraints, such as mates, hinges, or sliders, to simulate how parts
will move or interact within an assembly.
• Surfacing: Advanced CAD tools allow for complex surfacing,
enabling the creation of organic shapes, curved surfaces, and
complex geometries.
• Parametric Design: CAD software supports parametric modeling,
allowing designers to create and modify parts using parameters and
relationships, which enables easy iteration and design variations.
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52. Engineering Change Notice
• In engineering, the revision or ECN (Engineering Change Notice)
status of engineering drawings refers to the version or iteration of the
drawing and any associated changes that have been made. It helps
track and communicate the history of modifications and ensures that
the latest version of the drawing is being referenced and used.
• The revision status is typically indicated by a revision letter or number,
such as Revision A, Revision 1, or Revision 2. Each revision signifies a
significant change or update made to the drawing. When a revision
occurs, it is important to document the specific changes made, the
reason for the change, and the date of the revision.
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53. •ECN, on the other hand, refers to the process or
document that captures and communicates engineering
changes made to a drawing. An ECN typically includes
details about the proposed change, its impact on the
design, and any necessary approvals or reviews. It may
also include a description of the change, the affected
drawing number, the reason for the change, and any
associated documents or references.
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54. • The status of an engineering drawing may be indicated directly on the
drawing itself or in a separate document, such as the title block or revision
block. The revision status can be denoted by placing the revision letter or
number next to the drawing number, typically in a smaller font size or
within brackets. Additionally, the revision history or ECN log may be
maintained separately, tracking the changes made to the drawing over
time.
• By indicating the revision or ECN status, engineers, designers, and other
stakeholders can easily identify the most up-to-date version of a drawing,
ensuring that they are working with accurate and current information. It
also aids in maintaining a record of changes for future reference and
traceability
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55. Revision / ECN status of drawings
• An engineering change order (ECO) or an engineering change notice (ECN) is a
document that begins the process for making adaptations or corrections during a
product’s lifecycle. It plays a critical role in engineering and product development.
ENGINEERING CHANGE NOTICE
An engineering change notice (ECN) is an official notice that a change has been
approved. Many companies use a formal ECN to help ensure their contract
manufacturers and other manufacturing partners are building products correctly.
• They say the only thing constant is change – and the manufacturing process is
no exception. Although equipment, standards, and procedures take a good deal
of planning to establish, they are not set in stone. Machines and electrical
components evolve as they move towards newer models, while standards and
procedures are improving all the time
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57. What are the steps of an engineering change
process?
1. Identify the problem and the scope
2. Create an Engineering Change Request (ECR)
3. Review and approve the ECR
4. Create an Engineering Change Order (ECO)
5. Review and approve the ECO
6. Communicate the Engineering Change Notice (ECN) to
relevant groups
7. Implement the required change
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58. What are some types of changes that require
ECOs?
1. Typographical changes
2. Alternative manufacturers
3. Obsolete component
4. Design changes and new models
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59. Title Block Readings
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61. Drawing grid reading
• Grid drawing is a technique that will help improve your
accuracy without compromising the development of your
freehand drawing in the long-term. It basically involves placing a
grid over your reference photo and canvas, then using that grid
to assist with the placement of your drawing.
• The grid provides you with common reference points between
the photo and your canvas. It also allows you to break the
reference down into smaller and more manageable segments.
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CUSTOMER
SPECIFIC
REQUIREMENTS

63. Drawing Grid reading
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64. Drawing Grid Reading
• To help locate a specific point on a referenced print, most
drawings, especially Piping and Instrument Drawings (P&ID)
and electrical schematic drawings, have a grid system. The grid
can consist of letters, numbers, or both that run horizontally and
verticall
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65. Grid reading
• Grid reading in technical drawing refers to the process
of interpreting and extracting information from a grid
system that is superimposed on a technical drawing.
Grids are often used in technical drawings to provide a
visual reference for accurately locating and measuring
various elements within the drawing.
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66. Grid reading
• The grid system consists of evenly spaced horizontal
and vertical lines that intersect to form a series of
squares or rectangles. Each square or rectangle in the
grid is assigned a specific size or measurement, known
as the grid interval. The grid interval is typically
chosen based on the level of detail required for the
drawing.
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67. Grid Reference
• Each intersection point of the grid lines has a unique
reference or coordinate. The references are usually
labeled using letters for vertical lines and numbers for
horizontal lines. For example, the bottom-left
intersection may be labeled as A1, the top-right
intersection as D4, and so on. These references help
identify specific locations on the drawing.
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68. Positioning and Alignment
•The grid lines serve as guides for accurately
placing and aligning elements within the
drawing. By referencing the grid, you can ensure
that various components or dimensions are
correctly positioned relative to each other.
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69. Measuring Dimensions
•The grid system allows for precise
measurement of distances between
elements or features in the drawing. By
counting the grid intervals between two
points, you can determine the distance or
dimension accurately.
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70. Scaling
•The grid system can also be used to establish a
scale for the drawing. By defining the grid
interval as a specific measurement, such as one
centimeter or one inch, the drawing can be
scaled accordingly. This helps in converting the
drawing into real-world dimensions.
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71. Thank you
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