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POTONGAN
Menggambar Teknik TL
Sistematika
1. Membaca proyeksi ortogonal
2. Potongan
3. Materi Terkait Tugas
a. Skala
b. Tugas 3
MEMBACA PROYEKSI ORTOGONAL
Reading a drawing is the process of recognizing the shape of an object by interpreting the orthographic views.
DEFINITION
Orthographic Writing
Orthographic Reading
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F.V. R.S.V
T.V.
L.S.V
B.V.
VIEWING DIRECTION
Given
Analysis by Solids
ORTHOGRAPHIC READING
Objects are decomposed into solid geometric
primitives.
BASIC IDEA
Rectangular prism
Cylinder
Negative cylinder (Hole)
Some of familiar solid objects
Objects are decomposed into solid geometric
primitives.
BASIC IDEA
Cone
Pyramid
Sphere
Some of familiar solid objects
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READING STEPS
1. Orient yourself with the views given.
(Choose the viewing direction.)
2. Read the individual surfaces that appeared in
each view and related to each other.
3. Create a proper solid geometric primitive from
each reading.
4. Assembly all of solid geometric primitive
according to orthographic views.
EXAMPLE A
Given
Front View
Rectangular prism
Hole
Composition
Given
Rectangular prism
Composition
Front View
Cylinder
EXAMPLE B
Given
Cylinder with a blind hole.
Composition
L-shaped with round end
Hole
EXAMPLE C
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Composition
Wedge Given
EXAMPLE D Composition
Given
EXAMPLE D
L-shaped block
Wedge
Analysis by Surfaces
ORTHOGRAPHIC READING
2. Read the individual set of lines or surface that
appeared in each view and related to each
other.
1. Orient yourself with the views given.
An understanding in orthographic projection, i.e.
meaning of lines and surfaces are almost
important.
READING STEPS
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4. Repeat steps 2 and 3 until all surfaces are read.
During this repeating process, the details of
an object are added up until its completed
shape is obtained.
3. Mentally create and sketch a form of the surface
that produce the same orthographic views as
those at the beginning.
READING STEPS GUIDANCE 1
Adjacent areas that are not in the same plane must be
separated by lines.
Different plane
Line exists
Edge view
Same plane
Edge view
Top view
A
B
C
EXAMPLE
All surfaces A, B and
C are not in the same
plane.
Some of possible objects’ shape.
A
B C
A
B C
A
C
B
GUIDANCE 2
Areas that show a similar shape in more than one
view is the same surface.
Similar shape
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GUIDANCE 2
Areas that show a similar shape in more than one
view is the same surface.
POTONGAN
Object
GRAPHICS COMMUNICATION
WITH ENGINEERING DRAWING
Working
drawing
Clear ?
Orthographic
projection
(convention)
Section views
convention
Section Views
Orthographic
Projection
Finish
Yes
No
Dimensioning
PURPOSES OF SECTION VIEWS
Clarify the views by
Facilitate the dimensioning.
reducing or eliminating the hidden lines.
revealing the cross sectional’s shape.
Let See the example
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EXAMPLE : Advantage of using a section view.
ISTILAH DALAM POTONGAN
Cutting plane
CUTTING PLANE
Cutting plane line
Cutting plane is a plane that imaginarily cuts
the object to reveal the internal features.
Section lines
Cutting plane line is an edge view of the cutting plane.
CUTTING PLANE LINE
Indicate the path
of cutting plane.
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ANSI
standard
Thick line
Thick line
TS & ISO
standard
Thin line
CUTTING PLANE LINESTYLES
Viewing direction
Viewing direction
Viewing direction
This course
SECTION LINING
Section lines or cross-hatch lines are used to
indicate the surfaces that are cut by the cutting
plane.
Section lines
Drawn with thin lines.
SECTION LINES SYMBOLS
The section lines are different for each of
material’s type.
Cast iron, Malleable iron
Steel Concrete Sand Wood
For practical purpose, the cast iron symbol is
used most often for any materials.
SECTION LINING PRACTICE
The spaces between lines may vary from 1.5 mm
for small sections to 3 mm for large sections.
COMMON MISTAKE
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SECTION LINING PRACTICE
It should not be drawn parallel or perpendicular
to contour of the view.
COMMON MISTAKE
TREATMENT OF HIDDEN LINES
Hidden lines are normally omitted from section
views.
TIPE-TIPE POTONGAN
KIND OF SECTIONS
1. Full section
2. Offset section
3. Half section
4. Broken-out section
5. Revolved section (aligned section)
6. Removed section (detailed section)
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FULL SECTION VIEW
The view is made by passing the straight cutting
plane completely through the part.
OFFSET SECTION VIEW
The cutting plane is off-set to
include features that are not in a
straight line.
It is possible for the cutting plane
to change directions, to minimise
on the number of sectional views
required to capture the necessary
details.
OFFSET SECTION VIEW The view is made by passing the bended cutting
plane completely through the part.
Do not show the edge views of the cutting plane.
HALF SECTION VIEW A half-section is a view of an object showing one-half of the view in section. Symmetrical parts can be shown in half sections.
Half section without hidden lines
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HALF SECTION VIEW Half sections are commonly used to show both the internal and outside view of symmetrical objects.
HALF SECTION VIEW The view is made by passing the cutting plane halfway
through an object and remove a quarter of it.
HALF SECTION VIEW A center line is used to separate the sectioned half
from the unsectioned half of the view.
Hidden line is omitted in unsection half of the view.
It is common practice to section a part of an object
when only small areas need to be sectioned to indicate
the important details
BROKEN-OUT SECTION VIEW
The example shows a broken-out sectional view to indicate a through-hole in a plate.
The lines indicating the end of the section is a thin continuous line
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The view is made by passing the cutting plane normal
to the viewing direction and removing the portion of an
object in front of it.
BROKEN-OUT SECTION VIEW
A break line is used to separate
the sectioned portion from the
unsectioned portion of the view.
BROKEN-OUT SECTION VIEW
There is no cutting plane line.
Break line is a thin continuous
line (0.25) and is drawn
freehand.
EXAMPLE : Comparison among several section techniques
Revolved sections show cross-sectional
features of a part.
No need for additional orthographic views.
This section is especially helpful when a cross-section varies.
REVOLVED SECTION VIEW
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REVOLVED SECTION VIEW
Basic concept
REVOLVED SECTION VIEW
Basic concept
Given
Step 1
a. Assign position of cutting plane.
b. Draw axis of rotation in front view.
Steps in construction
REVOLVED SECTION VIEW
Edge view of cross-section
Steps in construction
Given
a. Transfer the depth dimension to
the front view.
REVOLVED SECTION VIEW
Step 2
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Steps in construction
Given
REVOLVED SECTION VIEW
a. Draw the revolved section.
Step 3
b. Add section lines.
Steps in construction
Given
REVOLVED SECTION VIEW
FINAL PICTURE
Placement of revolved section
1. Superimposed to orthographic view.
Superimposed Break
2. Break from orthographic view.
REVOLVED SECTION VIEW 6. Removed section
Removed section is revolved section.
Used where space does not enough for revolved section
Can be located elsewhere on a drawing with properly labeled
REMOVED SECTION VIEW
Section view is shown outside the view.
It may be appropriate to use removed sections, for webs, beams or arms,
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6. Removed section REMOVED SECTION VIEW
Note the absence of viewing arrows.
Example : Revolved vs. removed sections.
Revolved section Removed section
REMOVED SECTION VIEW
Example : Situation that removed section is preferred. REMOVED SECTION VIEW
Preferred Poor
Too messy !!
Example : Multiple removed section views REMOVED SECTION VIEW
A
A
B
B
SECTION A – A
SECTION B – B
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DIMENSI PADA POTONGAN
In most cases, dimensioning of the section views
follows the typical rules of dimensioning.
GOOD POOR
GOOD POOR
f 50
10
f 50
10
DIMENSIONING
For a half-section view,
use dimension line with
only one arrowhead that
points to the position inside
the sectioned portion.
f 50
DIMENSIONING
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