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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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