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8/6/2019 Lecturer 11 ing

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6/16/2011 Engineering Drawing & Graphics 1


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Computer Aided Design (Lecture # 08)

By

Nazeer Ahmad [email protected]

300-5397864

(Mechanical/Electrical Engineering)


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OutlineOBJECTIVE

INTRODUCTION

TYPES OF SECTIONING

TOPIC:

SECTIONAL VIEWS

CUTTING PLANESECTION LINES

PURPOSE OF SECTIONS


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OBJECTIVE

To demonstrate the proper use of section

views which show internal features of

objects that are not easily understood in

standard multi-view drawings


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Show internal detail

PURPOSE OF SECTIONS

Depict assembly of parts

Replace complex orthographic views

Describe materials in an assembly


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Objective:To make the drawing more understandable,

especially the internal details of the part.

Since the sectioned drawing shows internalfeatures there is generally no need to show

hidden lines.

Especially helpful for assembly drawings.

INTRODUCTION

Definition: A multiview technical drawing thatreveals details about internal features bydisplaying the part as if cut by an imaginary

cutting plane


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ANSI MATERIAL PATTERNS

ANSI31 -- Cast Iron, General

ANSI32 -- Steel

ANSI33 -- Brass, Bronze,

Copper

ANSI38 -- Magnesium,

Aluminum


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THE CUTTING PLANE

An imaginary plane that defines where the object is cut

Shown in drawing adjacent to the sectioned drawing

Drawn with the PHANTOM line type

Arrows at the end of the cutting plane line indicate the

direction of view for the sectioned drawing.

The arrows point toward the part of the object that is visible in

the sectioned drawing.A sectioned drawing follows the general rules of any view in

a multiview drawing


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THE CUTTING PLANE


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THE CUTTING PLANE

Occasionally cutting plane lines are not shown when

their location is obvious.The general section line type which may be used for any

material is the line type for iron.

When using multiple cutting planes each sectioned

drawing is drawn as if the other cutting plane lines do

not exist.

The cutting plane line takes precedence over center

lines.


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THE CUTTING PLANE


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RULES FOR SECTION LINES

Section lines should be oriented at different angles for

separate parts.

Occasionally section lines are only drawn on theperimeter of large areas.

Section lines are not used for thin parts rather they are

filled in solid (Do not use closely spaced section lines).

Section lines should not be parallel or perpendicular to

object lines.

Section lines are generally drawn at 45 degrees unless

this conflicts with other rules.


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SECTIONSSHOW INTERIOR DETAIL


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HALF SECTIONS

Half of view is cross-hatched

All hidden lines are omitted

Center line divides halves

A quarter of assembly removed

Center line remains only if associated feature is

sectioned


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HALF SECTIONS


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HALF SECTIONS


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HALF SECTIONS


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FULL SECTION

The cutting plane passes completely through the part as

a single flat plane

Hidden lines are omitted

Visible lines behind the cutting plane must be shown


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FULL SECTION


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FULL SECTION


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FULL SECTION


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BROKEN-OUT SECTIONS

Only a portion of the view is sectioned

A jagged break line is used to divide the sectionedand un-sectioned portion of the drawing

Used to section a small portion of a drawing

Does not modify the rest of the view


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BROKEN-OUT SECTIONS


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BROKEN-OUT SECTIONS


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REVOLVED AND REMOVED

SECTIONS

Both show cross- section by rotating section 90o

Revolved sections stay on the object

Removed sections are offset. A jagged break line may be used to divide the

revolved section from the rest of the drawing


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REVOLVED AND REMOVED

SECTIONS


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REVOLVED SECTION


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REVOLVED AND REMOVED SECTIONS


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Revolved section views are used toshow diverse shapes that may

appear in a part.

Here we see that the section lies on

the area it describes and may be

placed on top of object lines, or be

shown as part of a broken out

section to assist whoever is reading

the plate.


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REMOVED SECTIONS


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REMOVED SECTIONS

Removed sections allow the sectional view to be placed in another

area of the plate so as not to crowd

other views. All removed views are

labeled on their cutting plane and the

view.


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OFFSET SECTIONS

The internal features of many part can not be shownusing a single straight cut to create the sectioneddrawing

An offset section is used for such partsThe multiview drawing is often difficult to interpretwhen there are several hidden features on the object

A sectioned view makes the object much easier to

understand

An offset section allows the cutting plane to pass

through all of the internal features


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OFFSET SECTIONS


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OFFSET SECTIONS

6

There may beseveral bends in thecutting plane


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OFFSET SECTIONS

The actual part would show a new visible line at the bend

in the cutting plane

Since the cutting plane bend is arbitrary, do not show the

line representing this bend in the sectioned drawing orThe sectioned view does not show the bend in the cutting

plane

Hidden lines are not shown

Be sure to include object linesthat are behind the cutting

plane


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OFFSET SECTIONS


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ASSEMBLY SECTION

Shows how parts fit

together

Different parts have different

section line orientation

Different materials use

different section line types

Standard parts (shafts, pins,

dowels, rivets, screws,

washers, gears, etc.) are not

sectioned


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ASSEMBLY SECTION

Cut each part of the assembly

and section each part with the

appropriate section line type

Put the parts together in their

assembled position


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ASSEMBLY SECTION

The shaft is not sectioned

because it is a standard part

and section lines would

provide no additionalinformation

The orientation of section

lines clearly shows the

location of the different parts

The other two part are made

from the same material


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ASSEMBLY SECTION

The top and bottom mating

part are made from different

materials in the part shown

below

A center line is added to the

shaft to show that it is a

circular feature


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ASSEMBLY SECTION

When sectioning an

assembly of several

parts, draw sectionlines at varying

angles to distinguish

parts from each other.


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ASSEMBLY SECTION

Sectioned assemblies are used

to show relationships betweenparts.

NOTE: The hatching linesalternate direction on parts that

are adjacent to one another.

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