Thursday, June 22, 2006
Descriptive Geometry (Lecture 1 & 2)
Descriptive Geometry
What is descriptive geometry?
Descriptive Geometry is a study of points, lines and planes and their relationship in space. A knowledge of descriptive geometry is essential to solving 3-dimensional problems. Descriptive geometry graphically represents 3-dimensional problems on a 2-dimensional surface- “in this case”- your drawing paper.
It is based on the principles of orthographic projections. Solution involving descriptive geometry depends upon the use of frontal, profile, horizontal and auxiliary planes of projections.
Descriptive Geometry is the graphic representation of the plane, solid, and analytical geometry used to describe real or imagined technical devices and objects. It is the science of graphic representation in engineering design that forms the foundation, or grammar, of technical drawing.
After completing this course, the student will be able to:
1. Create auxiliary views of inclined planes
2. Use reference planes and fold lines when creating auxiliary views.
3. Explain auxiliary view projections theory.
4. Define primary, secondary and tertiary auxiliary views.
5. Define width, depth and height auxiliary views.
6. Create successive auxiliary views.
7. Create a partial auxiliary view.
8. Create a view in a specified direction using auxiliary view.
9. Define the theoretical principles of descriptive geometry.
10. Identify and define the direct view, revolution and axis rotations.
11. Draw different views of an object using the horizontal and vertical axis as applied to the front top and side view as point of reference.
12. Define and create the true-length view and point view of a line by the auxiliary method.
13. Locate a line or a point on a plane.
14. Identify, define and create parallel, intersecting, and perpendicular lines.
15. Construct true length lines in space.
16. Identify, define and construct parallel and perpendicular planes.
17. Determine the angle between a line and a plane, and between two planes.
18. Define and apply the principles of geometric intersections.
19. Identify, define and apply the intersection of lines and planes using the edge view method.
20. Identify, define and create the intersection of a plane and a solid using the cutting plane method.
21. Identify, define and create the intersection of a plane and a solid using the auxiliary view method.
22. Identify, define and create the intersection of two solids.
23. Identify, define and create the intersection of two planes.
24. Define and apply the theoretical principles of geometric developments.
25. Identify and classify the various types of developments.
26. Identify, define and create the developments of various solids and transition pieces.
Methods and Topics:
1. Intersections and developments
2. Fundamentals of descriptive geometry
3. Auxiliary views and revolutions
Source:
Technical Graphics communication by Bertoline, Wiebe, Miller & Nasman
Technical Drafting, Metric Design and Communication by Spence/Atkins
Prepared by:
Manuel C. Dacanay jr.
Instructor
AUXILIARY VIEW
There are times when one of the six principal views will not completely describe an object. This is true when there are inclined and oblique surfaces in the object. In these cases an auxiliary view can be created. The auxiliary view represents a true size view of an inclined plane.
An auxiliary view is an orthographic view that is projected onto any plane other than the frontal, horizontal or profile plane. An auxiliary view is not one of the six principal views.
An auxiliary view can be created by positioning a line of sight (LOS) perpendicular to the inclined plane.
There are two methods of creating auxiliary view : The fold-line method and reference plane method.
On the fold-line method, the object is imaginarily suspended in a glassbox to show the six principal views. However, when the object are projected, the six views does not represent the inclined plane in true size and shape; it always appears either on edge or foreshortened.
Another plane is then created to represent the 7th side of the box, this is what we call an auxiliary plane. The auxiliary plane is parallel to the inclined surface. The LOS required to create the auxiliary view is perpendicular to the new projection plane (auxiliary plane) and to the inclined surface. The auxiliary plane is perpendicular and connected by a fold-line to the frontal plane. The glass box is now unfolded with phantom lines identifying the fold-lines. In the auxiliary plane the 7th view (auxiliary view) is now projected in true size.
The reference plane method of creating an auxiliary is simply a variation of the fold-line method. In the fold-line method, the frontal plane is used as a projection surface to locate the fold-line that is used to construct the auxiliary view. This fold-line is used as a reference plane for transferring distances from the top view to the auxiliary view. The reference plane method is a technique that locates a plane relative to the object, instead of suspending the object in the glass box. The single plane (reference plane) is now use to transfer all the measurement necessary to produce the auxiliary view. The reference plane can be positioned anywhere relative to the object. The advantage of the reference plane is that, if positioned correctly, it can result in fewer measurements when constructing auxiliary views and it does not require a large working sheet to produce the unfolded glass box.
Auxiliary view classifications
Auxiliary views are created by positioning a new line of sight (LOS) relative to the object. It is possible to create any number of auxiliary views, including a new auxiliary view from an existing auxiliary view.
Primary auxiliary view – is a single view projected from one of the six- principal views.
Secondary auxiliary view – is a single view projected from a primary auxiliary view.
Tertiary auxiliary view – is a single view projected from a secondary or another tertiary auxiliary view.
Source:
Technical Graphics communication by Bertoline, Wiebe, Miller & Nasman
Technical Drafting, Metric Design and Communication by Spence/Atkins
Prepared by:
Manuel C. Dacanay jr.
Instructor
What is descriptive geometry?
Descriptive Geometry is a study of points, lines and planes and their relationship in space. A knowledge of descriptive geometry is essential to solving 3-dimensional problems. Descriptive geometry graphically represents 3-dimensional problems on a 2-dimensional surface- “in this case”- your drawing paper.
It is based on the principles of orthographic projections. Solution involving descriptive geometry depends upon the use of frontal, profile, horizontal and auxiliary planes of projections.
Descriptive Geometry is the graphic representation of the plane, solid, and analytical geometry used to describe real or imagined technical devices and objects. It is the science of graphic representation in engineering design that forms the foundation, or grammar, of technical drawing.
After completing this course, the student will be able to:
1. Create auxiliary views of inclined planes
2. Use reference planes and fold lines when creating auxiliary views.
3. Explain auxiliary view projections theory.
4. Define primary, secondary and tertiary auxiliary views.
5. Define width, depth and height auxiliary views.
6. Create successive auxiliary views.
7. Create a partial auxiliary view.
8. Create a view in a specified direction using auxiliary view.
9. Define the theoretical principles of descriptive geometry.
10. Identify and define the direct view, revolution and axis rotations.
11. Draw different views of an object using the horizontal and vertical axis as applied to the front top and side view as point of reference.
12. Define and create the true-length view and point view of a line by the auxiliary method.
13. Locate a line or a point on a plane.
14. Identify, define and create parallel, intersecting, and perpendicular lines.
15. Construct true length lines in space.
16. Identify, define and construct parallel and perpendicular planes.
17. Determine the angle between a line and a plane, and between two planes.
18. Define and apply the principles of geometric intersections.
19. Identify, define and apply the intersection of lines and planes using the edge view method.
20. Identify, define and create the intersection of a plane and a solid using the cutting plane method.
21. Identify, define and create the intersection of a plane and a solid using the auxiliary view method.
22. Identify, define and create the intersection of two solids.
23. Identify, define and create the intersection of two planes.
24. Define and apply the theoretical principles of geometric developments.
25. Identify and classify the various types of developments.
26. Identify, define and create the developments of various solids and transition pieces.
Methods and Topics:
1. Intersections and developments
2. Fundamentals of descriptive geometry
3. Auxiliary views and revolutions
Source:
Technical Graphics communication by Bertoline, Wiebe, Miller & Nasman
Technical Drafting, Metric Design and Communication by Spence/Atkins
Prepared by:
Manuel C. Dacanay jr.
Instructor
AUXILIARY VIEW
There are times when one of the six principal views will not completely describe an object. This is true when there are inclined and oblique surfaces in the object. In these cases an auxiliary view can be created. The auxiliary view represents a true size view of an inclined plane.
An auxiliary view is an orthographic view that is projected onto any plane other than the frontal, horizontal or profile plane. An auxiliary view is not one of the six principal views.
An auxiliary view can be created by positioning a line of sight (LOS) perpendicular to the inclined plane.
There are two methods of creating auxiliary view : The fold-line method and reference plane method.
On the fold-line method, the object is imaginarily suspended in a glassbox to show the six principal views. However, when the object are projected, the six views does not represent the inclined plane in true size and shape; it always appears either on edge or foreshortened.
Another plane is then created to represent the 7th side of the box, this is what we call an auxiliary plane. The auxiliary plane is parallel to the inclined surface. The LOS required to create the auxiliary view is perpendicular to the new projection plane (auxiliary plane) and to the inclined surface. The auxiliary plane is perpendicular and connected by a fold-line to the frontal plane. The glass box is now unfolded with phantom lines identifying the fold-lines. In the auxiliary plane the 7th view (auxiliary view) is now projected in true size.
The reference plane method of creating an auxiliary is simply a variation of the fold-line method. In the fold-line method, the frontal plane is used as a projection surface to locate the fold-line that is used to construct the auxiliary view. This fold-line is used as a reference plane for transferring distances from the top view to the auxiliary view. The reference plane method is a technique that locates a plane relative to the object, instead of suspending the object in the glass box. The single plane (reference plane) is now use to transfer all the measurement necessary to produce the auxiliary view. The reference plane can be positioned anywhere relative to the object. The advantage of the reference plane is that, if positioned correctly, it can result in fewer measurements when constructing auxiliary views and it does not require a large working sheet to produce the unfolded glass box.
Auxiliary view classifications
Auxiliary views are created by positioning a new line of sight (LOS) relative to the object. It is possible to create any number of auxiliary views, including a new auxiliary view from an existing auxiliary view.
Primary auxiliary view – is a single view projected from one of the six- principal views.
Secondary auxiliary view – is a single view projected from a primary auxiliary view.
Tertiary auxiliary view – is a single view projected from a secondary or another tertiary auxiliary view.
Source:
Technical Graphics communication by Bertoline, Wiebe, Miller & Nasman
Technical Drafting, Metric Design and Communication by Spence/Atkins
Prepared by:
Manuel C. Dacanay jr.
Instructor
// posted by deeyawnah @ 7:40 AM 
