MECHANICAL DRAWING

Different views of an objectObjects may be drawn in different ways

PictorialMultiview

•Better for showing true size and shape

•Each view only shows two dimensions

•Better for visualizing the object

•All three dimensions shown on a single view

Multiview Drawing

Multiview Drawing

A multiview drawing is one that shows two or more two-dimensional views of a three-dimensional object.

Multiview drawings provide the shape description of an object. When combined with dimensions, multiview drawings serve as the main form of communication between designers and manufacturers.

Multiview Drawing

• Another name for orthographic projection is multiview drawing

• Involves visualization and implementation– Ability to see clearly in the mind’s eye an object– Process of drawing the object

Angles of Projection

• First-angle projection– Used by many European countries– Object is projected onto planes

from the first angle or quadrant• Front view projected to vertical plane• Top view projected to horizontal plane• Left-side view projected to profile

plane

TOP VIEW

FRONT VIEW RSIDE

Angles of Projection

• Third-angle projection– Standard for the United States– Third quadrant is used for

projection• Front view projected to vertical

plane• Top view projected to horizontal

plane• Right-side view projected to

profile plane

1.63 1.25

5.13

2.00

2.88

2.25

1.50

2.50

3.50

45°Ø1.52

TOP VIEW

FRONT VIEW R. SIDEVIEW

Choosing Views

• Most commonly used views– Front View– Top View– Right Side View

• Most descriptive view is typically designated as the Front View

Choosing Views

• Complex objects require three views to describe its shape

• Simple objects can be described with two views– Ex: Soda Can

• Thin objects can be described with only one view– Depth is given in a note– Ex: Erasing Shield

1.63 1.25

5.13

2.00

2.88

1.751.50

2.00

3.00

Ø2.22

TOP VI EW

FRONT VI EW R. SI DE VI EW

45°

SPECI AL CAM R. MI GLI ORATO 5/ 9/ 03 SCALE 1:1 16-52 12 NBHS

Placement of Views

• Views should be visually balanced within the working space

Steps for Centering a Drawing

.75

.25

8.50

7.00

10.5011.00

.50

.25 .25

• Draw border and title block using light construction lines• Draw diagonal lines from corners of border

Layout of Views

Steps for Centering a Drawing

• Add:– Length 5.13– Space 1.50– Width 2.00 – Horizontal 8.63

– Height 3.00– Space 1.50– Width 2.00– Vertical 6.50

1.63 1.25

5.13

2.00

2.88

1.751.50

2.00

3.00

Ø2.22

TOP VI EW

FRONT VI EWR. SI DEVI EW

45°

4.3"

3"

4.3"

3"

Steps for Centering a Drawing

• Draw a box the size of all views• Measure from the center:

– Half the width– Half the height

FRONT VI EWR. SI DEVI EW

TOP VI EW

5.13 1.50 2.00

3.00

1.50

2.00

Steps for Centering a Drawing

• Draw in views using light construction lines

Adding Details

• Add holes and features• Transfer horizontal and vertical features• Use miter line to transfer depth

TOP VI EW

FRONT VI EW R. SI DE VI EW

SPECI AL CAM R. MI GLI ORATO 5/ 9/ 03 SCALE 1:1 16-52 12 NBHS

Straight Edges

• Edges that are parallel to a plane of projection appear as lines

• Edges that are inclined to a plane of projection appear as foreshortened lines

POI NT

VI EW

TRUE LENGTH

TRUE LENGTH

FORESHORTENED

FORESHORTENED

Curved Edges

• Curved edges project as straight lines on the plane to which they are perpendicular

• Curved edges project as curved lines on the planes to which they are parallel or inclined

Normal Surfaces

Normal surfaces appear as an edge in two opposite principal views, and appear a surface in all other principal views.

Inclined Surfaces • Inclined surfaces appear as an edge in two

opposite principal views, and appear foreshortened (not true size) in all other principal views.

Oblique Surfaces

• Oblique surfaces do not appear either as an edge or true size in any principal view.

NO LI NE

NOLI NE

Intersections & Tangencies

• Where a curved surface is tangent to a plane surface, no line should be shown where they join

Intersections & Tangencies

• Where a plane surface intersects a curved surface, an edge is formed

LI NE

LI NE

What is Multiview drawing?

Ortho (straight) + graphic (drawing)

An orthographic view is drawn looking straight at one side of the object (at 90° to it)

Drawing more than one orthographic view of an object on the same page

Line of sight

Projection plane

Object

Orthographic projection is a technique that is used to create multiview drawings.

Orthographic projection is any projection of the features of an object onto an imaginary plane of projection. The projection of the features of the object is made by lines of sight that are perpendicular to the plane of projection.

Orthographic Projection

The best way to understand orthographic projection is to imagine an object contained inside a glass box.

Orthographic Projection

There is a total of six glass walls surrounding the object. Each wall represents a projection plane onto which a two- dimensional object view will be created.

Orthographic Projection

A projection plane, also referred to as a plane of projection or picture plane, is an imaginary surface that exists between the viewer and the object.

The projection plane is the surface onto which a two-dimensional view of a three-dimensional object is projected and created.

Projection Plane

Start by focusing only on the front projection plane.

A person standing in front of the object would see only the five corners identified in black.

1

2

3

4

5line of sight

at 90° a

ngle

to projection

plane

Orthographic Projection

Projection lines are used to project each corner outward until they reach the projection plane.

Orthographic Projection

A projection line is an imaginary line that is used to locate or project the corners, edges, and features of a three-dimensional object onto an imaginary two-dimensional surface.

Projection Lines

The visible edges of the object are then identified on the projection plane by connecting the projected corners with object lines.

Orthographic Projection

The orthographic projection process is then repeated on the other projection planes.

Orthographic Projection

A Question…Each of the blocks to the right have the same overall dimensions and colors.What else to they have in common?

Answer ….

They all have identical top

views!

HIDDEN LINES MUTLIVIEW DRAWINGS

We place hidden lines in a drawing to do the following things:

1. Show hidden features

2. Clarify the position and shape of features

3. Make the “plate” more readable

(NOTE: The term “plate” refers to a finished drawing.)

How many views?Cubes (like these dice) have 6 sides

Since each side of the die will have its own view…then there must be SIX possible orthographic views!

Front

How many views?Cubes (like these dice) have 6 sides

Since each side of the die will have its own view…then there must be SIX possible orthographic views!

Front

Top

How many views?Cubes (like these dice) have 6 sides

Since each side of the die will have its own view…then there must be SIX possible orthographic views!

Front

Top

Right Side

How many views?Cubes (like these dice) have 6 sides

Since each side of the die will have its own view…

The Front, Top, and Right Side are the views that are usually drawn.

then there must be SIX possible orthographic views!

Front

Top

Right Side

Back

Bottom

Left Side

Where do the views go?All the views MUST be arranged correctly

Imagine “unfolding” the cube to get proper view alignment.

The back view can be placed in any of these four locations.

How does this work on other objects?

Place the object in a glass box

Top view goes above

Then “unfold” the box

R.Side view goes to the right

Front view is always central

What about details you can’t see?

Hidden lines show details that are not seen in all views

Draw hidden lines (dashed) to show the detail

Project from hidden detail to the other views

ANIMATED EXAMPLES

http://dossin.weebly.com/3-multi--view-orthographic-projection-drawing.html

Multiview Drawing REVIEWAn orthographic view is drawn looking straight at one side of the object (at 90° to it)

There are 6 possible orthographic views: Front, Back, Top, Bottom,

Left Side, Right Side

The Front, Top, and R.Side views are usually all that are drawn

Hidden lines show details you can’t see in all views

Centering a Multiview Drawing Review

Make a sketch of the views needed for the drawing.The space between the views is 1 ½”What are the measurements needed to center the drawing?What is the overall size of the box for the views?

Centering a Multiview Drawing Review

1.75

1.5

1.56.50

3.50

3.50

11.50

6.75

Layout of the 6 ViewsSketch the layout of the 6 views of this object and label the views.

TOP

FRONTREAR L. SIDE

BOTTOM

R. SIDE