Projection of Planes Engineering Drawing
A three-dimensional object tin be represented in a single airplane, such equally on a sail of paper, using projecting lines and planes. All projection theory is based on two variables: line of sight (projecting lines) and plane of project.
A line of sight (LOS) is an imaginary line between an observer's eye and an object. A airplane of projection (i.e., an image or picture plane) is an imaginary flat plane upon which the image is projected. The project is produced past connecting the points where the lines of sight pierce the projection plane. Equally a event, the 3D object is transformed into a second view.
If the distance from the observer to the object is infinite, then the projection lines are causeless to be parallel, and the projection is called a parallel projection. Parallel project is orthographic if the plane of projection is placed between the observer and the object, and the plane is perpendicular to the parallel lines of sight.
You can use parallel projection technique to create both multiview and pictorial (isometric and oblique) views.
- In multiview orthographic project (encounter details beneath), the object surface and the projection aeroplane are parallel, and you tin come across only ii dimensions.
- In isometric view (orthographic) the surface is no longer parallel to the projection plane, but the latter is perpendicular to the lines of sight, with three dimensions being seen.
- In oblique projection (non-orthographic) the object surface and the projection plane are also parallel, but the lines of sights are not perpendicular to the projection aeroplane, and you can see once more three dimensions.
If the distance from the observer to the object is finite, and then the project lines are not parallel (since all lines of sight start at a unmarried indicate), and the drawing is classified as a perspective projection. In perspective view the object surface and projection plane tin can be too parallel.
Multiview projection
Past changing position of the object relative to the line of sight you can create unlike views of the aforementioned object. Drawing more than i face of an object by rotating the object relative to your line of sight helps in understanding the 3D course. Having several views on one drawing you employ the concept of multi-view project, which is based on the orthographic (parallel) projection technique where
- the plane of projection is positioned between the observer and the object,
- the aeroplane of projection is perpendicular to the parallel lines of sight, and
- the object is oriented such that only 2 of its dimensions are shown.
Chief principles of creating multiview projections
The aeroplane of project can be oriented to produce an infinite number of views of an object. However, the most common views are the vi mutually perpendicular views that are produced by six mutually perpendicular planes of projection:
- Front view – the one that shows nigh features or characteristics.
- Left side view – shows what becomes the left side of the object after establishing the front view position.
- Right side view – shows what becomes the correct side of the object after establishing the front view position.
- Top view – shows what becomes the top of the object once the position of the front view is established.
- Lesser view – shows what becomes the bottom of the object once the position of the front end view is established.
- Rear view – shows what becomes the rear of the object one time the position of the front end view is established.
The well-nigh informative (descriptive) view of the object to be represented is usually chosen as the chief view (front view). This is view A related to the respective direction of viewing A and it usually shows the object in the performance, manufacturing, or mounting position.
View positions on drawings and corresponding viewing directions
Positions of the other views relative to the principal view in the drawing depend on the project method.
The number of views and sections must exist express to the minimum necessary to fully stand for the object without ambiguity.
Unnecessary repetition of details must be avoided.
Conventional view placement
Generally, three views of an object are enough, however, a drawing must contain as many views as necessary to illustrate the function, usually at correct angles to one another.
Frontal plane of projection
In multiview projection, the object is viewed perpendicular to the master faces, then that only one confront of the object is depicted in each view. The frontal aeroplane of projection is the plane onto which the front view of a multiview drawing is projected.
In the front view yous can see height and width of the object, but you cannot see its depth.
Horizontal plane of projection
The peak view is projected onto the horizontal aeroplane of project, which is plane suspended above and parallel to the top of the object.
The top view of an object shows the width and depth dimensions.
Profile plane of projection
In multiview drawings, the right side view is the standard side view. The right side view is projected onto the right profile aeroplane of projection, which is a plane that is parallel to the right side of the object. However, you tin can also use the left side view if it is more than descriptive and informative. Moreover, when needed, you can include both side views into one drawing.
The side view of an object shows the depth and height dimensions.
The three-view multiview cartoon is the standard used in engineering and technology, considering often the other iii common views are mirror images and do non add to the knowledge about the object.
The standard views used in a iii-view drawing are the
- peak,
- front, and
- right side views,
bundled as shown in the effigy:
The width dimension is common to the front and meridian views. The height dimension is common to the front and side views. The depth dimension is common to the top and side views.
For simple parts one or 2 view drawings will oft be enough. In one-view drawings the third dimension may exist expressed by a note, or by descriptive words, symbols, or abbreviations, such as Ø, HEX, etc.
Square sections may be indicated by low-cal crossed diagonal lines, as shown above, which applies whether the face is parallel or inclined to the drawing airplane.
Another case of a one-view drawing:
Additional views may be added if they meliorate visualization.
The views should as well be chosen to avert subconscious feature lines whenever possible. That means that the most descriptive view should be shown.
Also, you should select the minimum number of views needed to completely depict an object. Eliminate views that are mirror images of other views.
Why multiview drawings technique is so important?
To produce a new product, it is necessary to know its true dimensions, and true dimensions are not fairly represented in virtually pictorial drawings. For example, the photograph is a pictorial perspective prototype. However, as y'all can run into, the image distorts truthful distances, while the latter are essential for manufacturing and construction, and in this example the instance in question is the width of the road, not the electrical pole!
In mechanical technology perspective projections distort measurements.
As you can meet, the two width dimensions in the front view of the block appear different in length in the perspective projection. In other words, equal distances do non appear equal on a perspective cartoon.
Thus, since engineering and technology depend on exact size and shape descriptions for design, the best approach is to utilise the parallel projection technique (orthographic projection) to create multi-view drawings where each view shows simply two of the three dimensions (width, height, depth).
To summarize:
The advantage of multiview drawings over pictorial drawings is that multiview drawings shows the true size and shape of the various features of the object, whereas pictorials misconstrue true dimensions which are critical in manufacturing and construction.
ist & 3rd angles (drinking glass box)
What exactly y'all should identify on the right side project?
Is it that nosotros can meet from the left side, or from the right side of the object?
To answer these questions at that place are two unlike ways, based on two dissimilar principles
- First-Bending Project
- 3rd-Bending Project.
Third bending is used in Canada and the U.s.. Outset angle is used in Europe.
In third bending orthographic project the object may exist assumed to exist enclosed in a glass box.
Each view represents that which is seen when looking perpendicularly at each face of the box.
The resulted views are identified past the names as shown.
The front end, rear, and side views are sometimes chosen eleva tions, east.g., front elevation. The peak view may be termed the plan.
If desired, the rear view may be shown both ways – at the farthermost left or the farthermost correct. When this is not practical to show rear view at he farthermost left or right due to the length of the function, particularly with panels and mounting plates, the rear view should non exist projected upwardly or down, equally this would issue in its being shown upside down.
Instead, it should exist fatigued as if projected sideways, just located in some other position, and should be clearly labelled REAR VIEW REMOVED.
In first angle orthographic projections the object is considered equally being rolled over to either side, so that the right side of the object is drawn to the left of the front meridian:
It is mandatory to point the method of multiview projection by including the appropriate ISO (International Organization for Standardization) projection symbol – the truncated cone:
You should identify this symbol in the lower right-mitt corner of the drawing in or adjacent to the championship block.
Axonometric projection
It is one of the pictorial cartoon projections, which are useful for illustrative purposes, educational aids, installation and maintenance drawings, blueprint sketches, and the like.
The Greek give-and-take axon means axis and metric means to measure. Axonometric projection is a parallel projection technique used to create a pictorial drawing of an object by rotating the object on an centrality relative to a aeroplane of project.
Axonometric projections such every bit isometric, dimetric, and trimetric projections are orthographic, in that the project lines are all parallel, just the angle of views is so chosen that three faces of a rectangular object would exist shown in a single view.
Axonometric drawings are classified by the angles between the lines comprising the axonometric axes. The axonometric axes are axes that meet to course the corner of the object that is nearest to the observer.
When all iii angles are unequal the drawing is classified as a trimetric. When two of the 3 angles are equal the drawing is classified as a dimetric. When all iii angles are equal the cartoon is classified equally a isometric.
Although there are an infinite number of positions that can be used to create such a cartoon only few of them are used.
Enlarged item
To eliminate the crowding of details or dimensions, an enlarged removed view may be used.
- The enlarged view should be oriented in the same manner as the main view,
- the scale of enlargement must exist shown, and
- both views should be identified by one of the methods shown in the illustrations – with the leader line or with the circle line. The circle enclosing the area on the main view should be drawn with a thin line.
Source: https://www.mcgill.ca/engineeringdesign/engineering-design-process/basics-graphics-communication/projections-and-views
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