Engineering Drawing : Overview and Introduction

MEP 100: Introduction toENGINEERING VISUALIZATION

Harish HiraniAssociate ProfessorBlock II/354. Dept of Mech. Eng.I.I.T Delhi

0.5-0-3Learn by Doing

Course Objectives

To introduce students to:• Method of visualizing engineering

objects• Simple assemblies• CAD modeling and communicating

them to other professionals.

Course ContentsSketching concepts. Orthographic Projections and views

interpretation of drawings

Principles of Axonometric projections and Development of Isometric

Introduction of CAD package to construct a simple solid model

Dimensioning of Orthographic Views

Using a CAD package to construct solid models and generating orthographic, isometric, sectional views with dimensioning .

Sectioning in Orthographic views and assembly drawings

Assembly of components and generation of corresponding drawings. Animation of single dof machines in CAD

2D TO 3D

GRAPHICS: Art or Science of drawing

Systematic knowledge-base practice capable of resulting in predictable type of outcome.

Pr

RC

Pr

R

r

r

Drawing: Plane by Plane: 2D to 3D

3D by Sketching

Procedure to Sketch

Two stage extrusion

Only extrusion ?• Learn Pro-E.• Think few simple shapes.

Projection: Graphical representation of 3-D object on 2-D media (Paper/screen)

Thick Lines

Thin Lines

All projection lines are orthogonal to the projection plane:

Orthogonal Projections

Various Lines• Outline, Hidden, Center,

Construction, – Dimension, Cutting plane,

Phantom, break.

• Center line: – Where center lines cross, the short

dashes should intersect symmetrically.

– Center lines should not end at object lines.

• Line precedence: Outlines take precedence over all other lines, Hidden lines take precedence over centre lines.

Orthographic Projections

X

Y

Object in I quadrant = I angleObject in III quadrant = III angleObject in II or IV quadrant ??

Object in I quadrant = I angle

Object in III quadrant = III angle

ORTHOGRAPHIC PROJECTIONS:

Horizontal/Top Plane (HP / TP) Vertical/Front Plane ( VP /VP ) Side Or Profile Plane ( SP / PP)

Reference Planes:

FV is a view projected on VP.TV is a view projected on HP.SV is a view projected on PP.

DIFFERENT VIEWS of an OBJECT are PROJECTED on DIFFERENT REFERENCE PLANES OBSERVING PERPENDICULAR to RESPECTIVE REFERENCE PLANE

Front View (FV)Top View (TV)Side View (SV)

Different Views:

FVTVSV

HP VP PP

x y

FRONT VIEW

TOP VIEW

L.H.SIDE VIEW

FOR T.V.

ORTHOGRAPHIC PROJECTIONS

First Angle projection

Once F.V. (principal view) chosen, other views need to be arranged w. r. t. FV. I angle

III angle

Space for:FV: 90, 50TV: 90, 40 Space between FV & TVSV: 40, 50 Space between FV & SV(90+10+40) * (50+10+40)

x

Y

Block View All orthographic views must fit on the same sheet.

First angle projection method Third angle projection methodView in direction above FV, is placed underneath FV.

View in direction below FV, is placed above FV.

View seen from the right of FV, is placed on the left of FV.

View seen from the left of FV, is placed on the right of FV.

Most informative view of an object shall be used as the front view.

Selection of Views• Only those views that are necessary for a clear & complete

description should be selected.– Simple objects such as cylinder, bushing, etc. require only

two views (FV & SV/TV).• Avoid (unnecessary) repetition of detail.

• Choose view which provide desired explanation with minimum number of hidden lines.– Invisible lines are represented with short dashes. Such line always

starts with a dash in contact with the object line from which it starts, unless it forms a continuation of a visible line.

Primitive Shapes: basic shapes that can be used to make more complex structures.

Sheet Size

841 * 1189

594* 841

420* 594

297* 420

210 * 297

A3 sheet for Sketching.

A2 Sheet = (2*A3) for each lab

No of Hours Questions Weightage2 3-4 25%1 2 (Simple+difficult) 75%

Book: Warren Luzadder and Jon M. Duff, 2009, Fundamentals of Engineering Drawing withan Introduction to Interactive Computer Graphics for Design and Production, 11th Edition, PHI Learning.

FOR T.V.

FT

FRONT VIEW

TOP VIEW

L.H.SIDE VIEW


DRAW THREE VIEWS OF THIS OBJECTBY FIRST ANGLE PROJECTION METHOD

Mistakes ??

FOR T.V.


FT

FRONT VIEW

TOP VIEW

L.H.SIDE VIEW


FOR T.V.



FRONT VIEW

TOP VIEW

L.H.SIDE VIEW

X Y

FRONT VIEW

TOP VIEW

L.H.SIDE VIEW

F

T

Dimensioning• Lines, numerals, symbols, notes:

– Dimension line: Thin continuous line. Terminated by arrowheads.

– Extension line: Thin continuous line. ⊥ to feature– Arrowhead:

Closed/Open. Length = 3* Width.

– Note: Specific info about feature.

– Leader: Pointer connecting feature & note.

Dimensioning Symbols• φ : Diameter• Sφ : Spherical diameter• : Square• R : Radius• SR : Spherical radius• ∩ : Arc length

Procedure:break part down into a series of geometric

features (hole, projection, etc.)

apply dimensions to size each of the features

(Functional dimensions),

apply dimensions to control the location of the

features (Non-functional dimensions).

Dimensioning Multi-features

Common mistakes

Dimensions 25, 40, and φ12 are functional dimensions. Dimensions 20 and 12.5 are non-functional dimensions.

Common mistakes

Dimension lines should not end at object lines

Common mistakes

Each feature shall be dimensioned only once on a drawing.Each drawing shall use the same unit (i.e. mm)Centerline may be used in place of extension line.

Placing dimensions• Aligned system• Unidirectional system Use metric system.

All dimensions in Inches

Aligned Unidirectional

All dimensions can be read frombottom edge of drawing. Number is placed along line.

Place dimension (number) above lineso that it can be read from bottom/right hand edge of drawing

Scales• Ratio of the linear dimension of an element

of an object as represented in the drawing to the real linear dimension of the same element of the object itself. – Full size: 1:1– Enlargement scale: 50:1; 20:1; 10:1; 5:1; 2:1.– Reduction scale: 1:2; 1:5; 1:10; 1:20; 1:50.

X: 1 1: X

Scale shall be large enough to permit easy and clear interpretation of the information .

SV

TV

yx

FV

30

30

10

30 10 30

ALL VIEWS IDENTICAL!!!DRAW THREE VIEWS OF GIVEN OBJECTBY FIRST ANGLE PROJECTION METHOD

SV

TV

yx

FV

30

30

10

30 10 30

ALL VIEWS IDENTICAL!!!PICTORIAL PRESENTATION IS GIVEN


x y

FV35

35

10

TV

302010

40

70

DRAW FV AND TV OF GIVEN OBJECTBY FIRST ANGLE PROJECTION METHOD Mistakes !!!!!

10

R 10

R 15R 30

TV

10

30

50

10

35

FV

X Y

DRAW FV AND TV OF GIVEN OBJECTBY FIRST ANGLE PROJECTION METHOD


TOP VIEW

R 10

R 15

R 30

10

3050

10

35

Geometry with straight lines

• Triangle 180 60°• Rectangle/Square 360 90°• Pentagon 540 108°• Hexagon 720 120°• Heptagon 900 128.57°• Octagon 1080 135°

180321 =++ ααα1α

2α

3α o135=α

With any point O as centre and radius = OA, draw a circle.

Can we draw geometries without measuring angles ?

O

A B

From A draw a cord of length OA,which intersects circle at B.

Length OB will be ????

Equilateral triangle???C

Angle CAB = 120°

Method to make a hexagonal of side= AB.

D

E

E is middle point of line DB.

B

How to locate point 5:

Bisecting Line 4-6

Line

43

E4 65

A

4

6 P

B

5

7

8

C

D

E

AB=BC=CD=DE=EA

Drawing Arc between two straight lines

Arc radius R = 10 mm

Arc 1

Drawing Arc (R1) between Line & Arc (R2)

Drawing Arc (R) between two Arc (RA & RB)Arc 3

Procedure to Draw Orthographic Projections using dimensions

All dimensions are in Inches

F V

T V

R H S V

Axonometric projection

Difference?

Plane

Possibility of a number

of axonometric

Axonometric Projection

• Dimetric: Angles between two of axes are same. Two scale factors.

• Trimetric: Three scale factors.• Isometric: ISO MEANS SAME,

SIMILAR OR EQUAL. X, Y, Z are projected on three dimensional axes maintained at equal inclinations with each other (120°). Size is reduced. Single scale factor.

α

γβ

Importance of Isometric Drawing

• Understand overall shape, size & appearance of an object prior to it’s production.

Isometric drawing combined with orthographic projections provide completeDescription.

Vertical+ 30° to HP- 30° to HP

ISOMETRIC AXES and LINES:

Three lines AL, AD and AH, meeting at point A and making 1200 angles with each other are termed Isometric Axes.

H

A

SOME IMPORTANT TERMS:

Lines parallel to isometric axes are called Isometric Lines.

Lines for hidden edges are generally not shown.

Representation of three planes

SHAPE Isometric view if the Shape isF.V. or T.V.

A

B

RECTANGLED

C

H D

A

B

C

A

B

D

C

FRONT VIEW of FIGURE requires

H & L AXES.

Vertical linewill be drawn vertical, while

horizontalline will be

drawn inclinedat 30° to

horizontal.

TOP VIEW of FIGURE require D

& L.

H

A

Making Isometric Drawing of Rectangular Object

L

H

D

F.V.

T.V.

Concept of block views

SHAPE Isometric view if the Shape isF.V. or T.V.

TRIANGLEH

1

2

3

A

B3

1

2

A

B

3

1

2

A

B

H

1

2 3

4PENTAGON

A

B C

D

E 1

2

3

4

A

B

C

D

E

1

2

3

4

A

B

C

DE

Shapes containing

Inclined lines cannot be drawn parallel to any isometric axes. Angle do not increase or decrease in any fixed proportion.

Enclose in a rectangle… First draw isom. of that rectangle and then inscribe that shape as it is.

Inclined Lines ????

Nonisometric Lines• Inclined lines (not

parallel to isometric axes).– Distorted (cannot be

measured directly) line.

– Position & Projected length must be established by locating end points.

FV

TV

A

B

C D

A

B

C

ISOMETRIC VIEW OFHEXAGONAL PRISM

STANDING ON H.P.

For hexagonal, angleis 120°

Edge aLength (0.5+1+0.5) aHeight (0.866 + 0.866) a

Isometric drawing for given orthographic projections.

Isometric Scale

h

d

a cg

f

e

b

b’

e’ g’f’

a’ c’

h’

d’ 30cos45cos

=Scale

816.0866.0707.0

==Scale

Foreshortening is ignoredIsometric drawing.

Otherwise projection.

o Angle cbp > angle obp

Length bc > bo

p

Lines for hidden edges are generally not shown

.

40

ISOMETRIC Drawing

Draw isometric lines, then

non-isometric

20

60

X Y

FV

TV

First angle orthographic projections

O

10

x y

FV SV

TV

ALL VIEWS IDENTICAL

40 60

60

40

10

F.V., T.V. and S.V.of an object are given. Draw it’s isometric view.

Isometric Drawing of Curved features

GIVEN: A circle in FVREQUIRED: Isometric view.

FIRST ENCLOSE IT IN A SQUARE. USE H & L AXES.

Four-centre Method: Ends of Small diagonal provides twoCenters. Locate two centers on longer Diagonal Easier for free hand sketching.

Ellipse is made of four arcs.

Drawing circles ??

25 R

100 MM

50 MM

IF TOP VIEW

IF FRONT VIEW

DRAW ISOMETRIC VIEW of the figure shown considering it first as FV and then TV.

CYLINDER, When Axis is Horizontal

CYLINDER, when Axis is Vertical

50

50

φ 30

30

10

30

+

FV

TV

ISOMETRIC Drawing

O

F.V. & T.V. of an object are given. Draw it’s isometric view.

40

10

50

80

10

φ 3025

FT

25

Block of 80*50*10

Block of 25*25*40

Four center method to draw ellipse

O

FV

TV

X YO

40

10

25

25

30 R

10

100103010

R 10


Cuboid of 100*50*10

Draw parallel lines at 30 mm

Cuboid of 50*25*40

Isometric Drawing of Curved features

O

O10

10

30

10

30

4020

80

30

F

T


Block of 80*40*10

Block of 60*10*30

First angle projection

O

15

15

O

F.V. and S.V.of an object are given in I angle projection. Draw it’s isometric view.

Sq 20

O

20

2010

30

60

30

40

100 50

40

F.V.

Mistake ??

40

40

FT

50

20

25

25 20


LSV

Y

25

25

1050

FV

X

10 10

15O


Sectional Views

79

Required to add information of surfaces that are represented by hidden lines in standard FV, TV, and SV.

what we need1. Cutting plane2. Part, assembly, any view.

Cross sectionSection

Section (thin parallel) lined areas are those portions that came in actual contact with cutting plane.

Visible parts behind the cutting plane are shown, but not hatched.

Section lines

Hatching Pattern Continuous thin lines at convenient angle (preferably 45°) to the principal outlines.

Common MistakesSpacing between the hatching lines should be chosen in proportion to the size of the hatched areas, provided that the requirement for minimum spacing are maintained.

Full section view

NOTES

84

• Sectional views are always viewed in the direction defined by cutting plane arrows.

• Any hidden surface that is behind cutting plane is not included in sectional view.

Hatch lines represent location of cutting plane passing through solid material.

Full & Half section views

Example: Sectional Orthographic Views

86

AA Mistakes in dimensioning?

Representation of cutting plane?

Section B-B

Section A-A

Rib not sectioned

a b c

Common mistake is to omit back edge

Sectional view of Ribs

88

Ribs add strength and rigidity to an object. Usually narrow.

Pg. 167 Luzadder book

89

• Although the spoke is in line with the front view, it can give the impression that it is a stunted spoke

• Full length of spoke is shown to indicate the structure. It should be shown along with front view to indicate the number of spokes and angles between them

Front view

Keyway

90

Revolved sections

Section rotated 90o

so that exact shape can be viewed

Cutting plane

Examples of Revolved Sections

Revolved sections examples show the shape of an object’s cross-section superimposed on a longitudinal view

Removed SectionsRemoved sections are like revolved sections but moved aside.

A

A

Section A-A

C CSection C-C

B

B

Section B-B

Offset Sections• Cutting plane lines need not be drawn as straight

lines Stepped line

93

Offset full section

Include as many features as possible without causing confusion

94

Countersunk hole

Choosing Full/Half/Broken sectional view

95

Half & Partial sectional views --- allow showing outer and inner features on the same figure.

Normal half/partial orthographic projection may include hidden lines.

Broken line is a freehand line.

Cutting Plane Lines

96

Phantom line

Section B-B

Section A-A

ALIGNED SECTIONS• To include, in a section, certain angled elements,

cutting plane may be bent so as to pass through those features.– Plane & feature are aligned into original plane.

98

Summary• When a part is cut fully in half, the resulting view is called

a full section.• A line called the cutting-plane line shows where the object

was cut and from which direction the section is viewed.– The arrows point toward the section being viewed.

• In section view, the areas that would have been in actual contact with the cutting plane are shown with section lining.

• Visible edges of the object behind the cutting plane are generally shown because they are now visible but they are not cross-hatched.

• Section views can replace the normal top, front, side, or any other standard orthographic view.

Summary

• When a cutting plane coincides with a center line, the cutting plane line takes precedence.

• Omit hidden lines in section views.• A section-lined area is always completely bounded

by a visible outline

Labeling !!

Summary• To avoid a false impression of thickness and

solidity, ribs/webs, gear teeth, and other similar features are not hatched with section lining even though the cutting plane slices them.

• Sectional views are important for assemblies.

102

3-D Solid ModelsSheet 8-13

106

Assembly Subassembly Component / Part

How to create solidmodel in Autodesk

Extrusion

• Select New > New , to make the sketch

• To start with select Metric > Standard (mm).ipt

Standard format with datum plane & Coordinate system. Dimensions in mm

• The following screen will be open to draw the sketch.

Choose line command to initialize the drawing

• After drawing a line provide the required dimension by choosing dimension option in panel, and clicking on the line.

Dimensions !!!! Before completing sketch ?????

• To provide angular dimension, select lines between which the angle is to be given.

• Complete the sketch by above mentioned tools.

Press finish when sketch is competed.Make sure sketch is closed i.e. there should be no free ends in the sketch.

• Press extrude to make a solid out of sketch

• Distance = part thickness.

•The arrow shows the direction of material addition.

• To change the direction of the material addition click on the icon shown in the extrude command.

To finish your model click “OK”.

Software Autodesk Inventor Professional

• Available in CSC window machines (9am –9 pm).

• Students can download software from http://students.autodesk.com/?nd=download_center

• Register using email id and get license key.• Evaluation:

– Submit print-out of drawings. One page per question. • How do I make title block• Import (download) mep100.dwg format.

117

Open Autodesk Inventor>click on new>metric>MEP100_A4>OK

Zoom in the title block at bottom right corner

Click annotate>text and click near the name field

Write your name and click OK

Similarly write entry no., group no. and lab no. to complete the title block

Complete the title block and zoom out to place the views

To create the drawings clickPlace Views>Base>file>orientation>style>ok

Place views and right click to create

Block views

Click Dimension > select entity > set precision

Complete dimensioning and save the file then print

Topics• Extrusion – Cut• Loft (Connecting

different cross sections)

• Ribs• Datum Planes• 2D to 3D

Starting Autodesk Inventor

Make solid model of orthographic projection given below and obtain orthographic views using mep100.dwg.

Step 1: Go to New and choose Standard(mm).ipt

Starting with Top plane

Step 2: Choose top plane to start the sketch. Use Model tree to select it. Draw a square of side 70mm

Step 3: Finish sketch and extrude the sketch

Step 4: Select the extruded surface to sketch on it

Step 5 :Draw a circle of 60 mm diameter and extrude it

Step 6: Select the extruded surface to sketch a square of 25mm on it. Finish the sketch

Step 7: Take a plane offset by 40 mm from the sketch plane.

Step 8: Select the offset plane to sketch a point in the middle

Step 9: Use loft command. First select the square sketch and then the point on offset plane and a loft will be created . Save the Part model.

Step 10: Go to drawing by Selecting ‘Drawing option’ from New command window. And select Base to place orthographic views.

Step 11: Select the part model for which orthographic views are required

Step 12: Place orthographic views and right click on a view to select create.

Step 13: From Annotate option choose dimension for dimensioning of orthographic views. Save the file after dimensioning is complete.

Draw the top view in the sketch and extrude it

Select the top surface for sketch and draw two circles and extrude them for the holes

Select the side surface and draw circles at a distance of 80 m from top surface. Extrude it.

Select the same surface for sketch and draw the profile as shown and extrude it

Select the side plane for sketch (which is passing through centre of circles). Select a line right click on sketch plane to make sure that Auto Project is on

Draw a line passing through intersection of two surfaces as shown by white lines representing intersection of rib.

Finish the sketch and select Rib command.

Select the lines for profile of Rib. Make sure Parallel to Sketch Plane option is selected. Give Rib thickness and press OK.

As the mid surface is chosen for sketch Rib thickness should be provided on the mid surface.

Obtain orthographic views and dimension them

Draw two squares and extrude them

Select a surface and draw a square of side 40mm and extrude it

Repeat the procedure on remaining surface to get a part as shown

Obtain orthographic projections and dimension those

TOPICS Other than extrusion

PATTERNLOFTCONSTRAINTSREVOLVESHELLSPLITCOMBINESPLINESWEEP

Features appearing more than once

How I make it ?????

LINEAR PATTERN

Making a Chocolate !!!!

RECTANGULAR PATTERN !!

CIRCULAR PATTERN

Pattern

Creating Datum Plane

Pattern

Visibility

Rectangular Pattern

Circular Pattern

LoftSketches on Datum planes

Revolve

SweepSection + Path

Assembly

On clicking

Assembly

Sub-assembly

Components

Construction of AssemblyStep 1: Gather components in an assembly file.

Step 2: Assemble components by applying appropriate assembly constraints.

Design Approaches

Bottom upTop downHybrid

Bottom PartTop Assemble

Top Down

Bottom Up

Six numbers of part2

Hybrid

Query: Meaning of constraint? Constraint = Restriction. Applied to 2D or 3D geometry. Two types of constraints: dimensional & geometric.

Dimensional constraints are used to control the length, angle, radius etc.

Geometric constraints are used to control the relationships of objects in respect to each other.

Query: Assembly constraints?Assembly constraints determine how components in the assembly fit together. As you apply constraints, you remove degrees of freedom, restricting the ways components can move and positioning them relative to one another.

•Press constraint

located near the top of the left column

Now select a constraint which you need (for example Mate, Angle, Tangent, and Insert)

MATEMate: makes the selected planes face each other and coincide (they are become the same plane)

Flush: makes the selected planes face the same direction and coincide

A mate constraint causes two selectedobjects (face, edge, vertex) to mate (opposite direction) or flush (same direction). Face to a faceAn edge to an edgeA point to a pointAn edge to a faceA vertex to a faceA vertex on an adge

Mate

Mate-offset ??

Mate-Mate + Mate-offset_flush

TANGENT

Example

INSERT

Drawing….

Assembly • Part 1……. Part n.

– Color

Assign to selection

Parameters & Relationship• Dimension is a parameter..

D0, d1, d2, ………..• Relationship may be made

in parameters.– Length by diameter should be

10.

Parameters & Relationship….

No change !!!

Threads

Threads… Internal

Assembly – Threaded Connection

Axial AlignMovement along the axis is possible.

Threaded ConnectionInsert.Rotation is possible.

Suppress

Checking Degrees of Freedom

Section• Choose/Make work

feature plane.

Offset ???

Bolted Connections

Exploded View…. Part of presentation• After assembly.

How do I Start

Now define the coordinate system about which part is going to displace First select the direction then the component

Each time you have to define the coordinate system for tweaking different components and if you don't define the coordinate system, then Software will take the last coordinate system which you have defined.

Now lets animate & see what we have done and whatimprovement are required

• End of Lecture 12

Engineering Drawing : Overview and Introduction

Documents

Transcript of Engineering Drawing : Overview and Introduction