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Lesson
7: Drawing the Base Bracket in Ortho, Iso and 3d |
FIG. 7a (the Base Bracket)
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In lesson 7 you will be drawing a object called the
base bracket, an object that has its place in many
areas of machining, and machine parts. Its function
is to hold one part against another with an adjustable
slide.
This is a challenging model because regions are
created from circles that are connected from quadrant
to quadrant on the circles. By using the trim command
you can create a multiple regions that can be extruded
and then subtracted from either of the base surfaces.
The 3d model is created from these multiple regions.
This particular model involves using ellipses that
can be rotated into position and connecting lines
that are arc tangent to circles.This part requires
the use of multiple center an hidden lines in its
multi views.
Overall, this is the most challenging of all models
thus far in dimensioning, isometrics and in the creation
of the 3d model.
Connecting Your Learning
As you work your way through this lesson, you should
reflect on the following questions:
How did the base bracket get its name?
What is an ellipse and how is it used in this model?
What is an Iso ellipse and how can it be rotated in
ACAD?
How will the base bracket model be created in 3d?
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The State of Arizona has assembled Drafting
standards to make sure that Instruction is thorough
and well thought out by the instructor. By clicking
on the hyperlink below will upload to your browser window
the entirety of these standards. The standards that
are addressed in this lesson are below the hyperlink.
1.0 USE BOARD DRAFTING EQUIPMENT,
INSTRUMENTS AND MEDIA.
2.0 DEMONSTRATE SKETCHING, LETTERING,
AND LINE SKILLS.
- 2.1 Demonstrate freehand sketching skills for drafting
applications.
- 2.2 Demonstrate lettering skills.
- 2.3 Demonstrate line work.
6.0 DEMONSTRATE GEOMETRIC CONSTRUCTIONS
- 6.1 Measure Geometric Constructions.
- 6.2 Develop Geometric Constructions.
8.0 APPLY BOARD DRAFTING SKILLS TO COMPUTER-AIDED
DESIGN/DRAFTING (CADD)
- 8.1 Demonstrate computer skills for a CADD system.
- 8.2 Create dimensional CADD entities.
- 8.3 Create 3 dimensional CADD drawings.
The State of Arizona has also assembled Math
standards and many of these apply directly to
the vocational subject area of Drafting. Drafting
is a very precise discipline and the use of mathematics
is integral to design and manufacturing. Below are
the math standards that are involved in this lesson
1M-P1. Compare and contrast
the real number system and its various subsystems
with
regard to their structural characteristics
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PO 2. Compare subsets of the
real number system with regard to their properties
(commutative, associative, distributive, identity,
inverse and closure properties)
1M-P2. Construct, interpret and
demonstrate meaning for real numbers and absolute
- PO 3. Solve real-world distance problems using
absolute value
- PO 4. Determine, among the solutions to a real-world
problem, which, if any, is reasonable
- PO 2. Define absolute value as the distance from
the origin
4M-P1. Interpret and draw three-dimensional
objects
- PO 1. Sketch prisms, pyramids, cones, cylinders
and spheres
- PO 2. Classify prisms, pyramids, cones, cylinders
and spheres by base shape and lateral surface shape.
- PO 3. Recognize the three-dimensional figure represented
by a two-dimensional drawing.
- PO 5. Make a model of a three-dimensional figure
from a two-dimensional drawing and make a two-dimensional
representation of a three-dimensional object (models
and representations include scale drawings, perspective
drawings, blueprints or computer simulations)
4M-P4. Deduce properties of,
and relationships between, figures from given
assumptions
- PO 1. Find similarities and differences among
geometric shapes and designs using a given attribute
(e.g., height, area, perimeter, diagonals and angle
measurements)
- PO 2. Identify arcs, chords, tangents and secants
of a circle
- PO 3. State valid conclusions using given geometric
definitions, postulates and theorems
- PO 4. Represent pi as the ratio of circumference
to diameter
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Lesson
Objectives
By the end of this lesson you should be
able to:
1. Draw the orthographic views of the
base bracket and dimension the model.
2. Identify the isometric angles used to create isometric
views (30, 90 and 150 degrees)
3. Scale down the orthographic view and create an Isometric
view.
4. Adjust the dimscale overall and linear to reflect
full scale dimensions in the ortho/iso drawing.
5. Create the 3d model of the base bracket from the
top orthographic view.
6. Working with colors for visualization enhancement.
7. Maintain approximate proportions using "boxing
in" also called the "Glass box Technique"
8. Create and locate the accurate use of center lines
in orthographic drawings.
Key
Terms
"click
on the key on any of these terms and it will hyperlink
to the course glossary" |
The 7th model
you will be drawing is called the base bracket and it
is a model where all the views are necessary to illustrate
its attributes. The illustration of the base bracket isometrically
involves circles that are connected to one another to
create an adjustable slot.
Insert your
Lesson 7 media disk into your CD drive and begin listening
to the avi file: lesson 7a. You can open up both software
programs: ACAD and your media player at the same time
and toggle back and forth between screens, and be able
to draw and listen simultaneously.
Below is
an example of what your completed drawing should look
like. Pay attention to details so you can obtain all your
points for this assignment. It is always better to get
it right the first time, especially when you have what
the finished product should look like. I will mention
in the media files about the Dim-scale of the dimension
text.
The next part of Lesson 7 you will be creating
the Isometric view of the base bracket. this is a challenging
object to do Isometrically. This is where our talent begins
to develop in conceptualizing what this model really looks
like. In this lesson you will be scaling your orthographic
views and adjusting the linear dimscale accordingly. Common
sense will say if a scale something to half its size the
dimension scale needs to be doubled. I will explain this
in the lesson disk titled Lesson 7b. The following is what
your completed assignment should look like when completed.
Please Insert the Media Disk labeled Lesson
7 into your CD drive of your computer and begin listening
how to draw the 3d model of the base bracket. The lesson
avi is titled Lesson 7c and below is an example of a completed
accurate model of the base bracket. You will submit your
drawing in South East Isometric. This is what your completed
3d assignment looks like.
*Note:
The Lessons are best viewed with real player, or Windows
Media Player 9 for 2000 Professional and Version 10 for
XP.
After
completing each lesson attach your drawing to an email and
send to your Instructor's email.
email:
losimilar@yahoo.com
Your
Text Book and Reading Assignments
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Text:
Autocad Drafting by
Grout, Resetarits and James
Use
this text as a reference to the media disks that you
are using for the Semester.
Lesson 7 assessment comprises:
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Lesson 7a submitted as a dwg. file
(10 pts.)
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Lesson 7b submitted as a dwg. file.(10
pts.)
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Lesson 7c submitted as a dwg. file.(10
Pts.)
Rubrics for Grading: The drafting
standards for assessing the quality and accuracy of your
drawings are as follows: Neatness, Accuracy and Lines and
Lettering. One half of one point (.5) will be taking off
your score in relation to NALL.
Submit by email attachment all of
the above lessons as dwg. files and send to your Instructor
whose mail address is. losimilar@yahoo.com
Your Instructor will grade your drawings
within 24 hours and email you back the grade/assessment
of your work. You should take allot of pride in your work.
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