What Is Plane of Projection in Engineering Drawing
A iii-dimensional object tin exist represented in a single plane, such as on a sheet of paper, using projecting lines and planes. All projection theory is based on 2 variables: line of sight (projecting lines) and plane of projection.
A line of sight (LOS) is an imaginary line between an observer's eye and an object. A plane of projection (i.e., an paradigm or flick plane) is an imaginary apartment plane upon which the image is projected. The project is produced by connecting the points where the lines of sight pierce the project airplane. Equally a result, the 3D object is transformed into a 2D view.
If the distance from the observer to the object is space, and so the project lines are assumed to be parallel, and the projection is called a parallel projection. Parallel projection is orthographic if the airplane of projection is placed between the observer and the object, and the airplane is perpendicular to the parallel lines of sight.
You tin can use parallel projection technique to create both multiview and pictorial (isometric and oblique) views.
- In multiview orthographic projection (see details below), the object surface and the projection plane are parallel, and you can come across only ii dimensions.
- In isometric view (orthographic) the surface is no longer parallel to the project plane, just the latter is perpendicular to the lines of sight, with 3 dimensions being seen.
- In oblique project (non-orthographic) the object surface and the projection plane are too parallel, but the lines of sights are not perpendicular to the projection aeroplane, and yous can see again three dimensions.
If the distance from the observer to the object is finite, then the project lines are not parallel (since all lines of sight start at a single indicate), and the drawing is classified every bit a perspective projection. In perspective view the object surface and projection aeroplane can be also parallel.
Multiview project
By changing position of the object relative to the line of sight you can create different views of the same object. Drawing more than one face of an object by rotating the object relative to your line of sight helps in understanding the 3D form. Having several views on one drawing you use the concept of multi-view projection, which is based on the orthographic (parallel) projection technique where
- the plane of projection is positioned between the observer and the object,
- the plane of projection is perpendicular to the parallel lines of sight, and
- the object is oriented such that just ii of its dimensions are shown.
Main principles of creating multiview projections
The plane of projection tin exist oriented to produce an infinite number of views of an object. However, the about common views are the half dozen mutually perpendicular views that are produced by half dozen mutually perpendicular planes of projection:
- Front view – the one that shows most features or characteristics.
- Left side view – shows what becomes the left side of the object after establishing the forepart view position.
- Right side view – shows what becomes the correct side of the object afterwards establishing the front view position.
- Top view – shows what becomes the top of the object in one case the position of the front view is established.
- Bottom view – shows what becomes the lesser of the object once the position of the forepart view is established.
- Rear view – shows what becomes the rear of the object once the position of the front view is established.
The near informative (descriptive) view of the object to be represented is ordinarily called as the principal view (front view). This is view A related to the corresponding direction of viewing A and information technology usually shows the object in the functioning, 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 projection method.
The number of views and sections must be limited to the minimum necessary to fully correspond the object without ambiguity.
Unnecessary repetition of details must be avoided.
Conventional view placement
By and large, three views of an object are plenty, still, a drawing must contain every bit many views equally necessary to illustrate the office, normally at right angles to one some other.
Frontal airplane of projection
In multiview projection, the object is viewed perpendicular to the primary faces, then that only ane confront of the object is depicted in each view. The frontal plane of project is the plane onto which the front view of a multiview drawing is projected.
In the front view you can see height and width of the object, simply you lot cannot see its depth.
Horizontal plane of project
The top view is projected onto the horizontal airplane of projection, which is aeroplane suspended above and parallel to the top of the object.
The height view of an object shows the width and depth dimensions.
Contour airplane of projection
In multiview drawings, the right side view is the standard side view. The right side view is projected onto the right profile plane of projection, which is a plane that is parallel to the correct side of the object. Even so, y'all can besides use the left side view if it is more descriptive and informative. Moreover, when needed, y'all tin include both side views into ane drawing.
The side view of an object shows the depth and height dimensions.
The three-view multiview cartoon is the standard used in engineering science and technology, because ofttimes the other three common views are mirror images and do not add to the cognition most the object.
The standard views used in a three-view drawing are the
- top,
- front end, and
- right side views,
arranged every bit shown in the figure:
The width dimension is common to the front and top views. The tiptop dimension is common to the front and side views. The depth dimension is common to the superlative and side views.
For unproblematic parts 1 or two view drawings will often be enough. In ane-view drawings the third dimension may be expressed past a notation, or past descriptive words, symbols, or abbreviations, such as Ø, HEX, etc.
Square sections may be indicated by calorie-free crossed diagonal lines, as shown in a higher place, which applies whether the face up is parallel or inclined to the drawing plane.
Some other instance of a one-view drawing:
Additional views may exist added if they amend visualization.
The views should also be called to avoid hidden characteristic lines whenever possible. That ways that the well-nigh descriptive view should be shown.
Besides, you should select the minimum number of views needed to completely describe an object. Eliminate views that are mirror images of other views.
Why multiview drawings technique is and so important?
To produce a new product, it is necessary to know its true dimensions, and true dimensions are non adequately represented in most pictorial drawings. For example, the photograph is a pictorial perspective epitome. Withal, as you can see, the image distorts true distances, while the latter are essential for manufacturing and construction, and in this case the case in question is the width of the road, not the electrical pole!
In mechanical engineering perspective projections distort measurements.
Equally you lot tin encounter, the 2 width dimensions in the forepart view of the cake appear unlike in length in the perspective project. In other words, equal distances practice not appear equal on a perspective drawing.
Thus, since engineering and technology depend on verbal size and shape descriptions for pattern, the all-time approach is to utilise the parallel projection technique (orthographic project) to create multi-view drawings where each view shows only two of the three dimensions (width, elevation, 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 distort truthful dimensions which are critical in manufacturing and construction.
1st & threerd angles (drinking glass box)
What exactly you should identify on the right side project?
Is it that we can encounter from the left side, or from the right side of the object?
To respond these questions there are two different means, based on two different principles
- First-Angle Projection
- 3rd-Angle Projection.
Third angle is used in Canada and the United States. First angle is used in Europe.
In tertiary angle orthographic projection the object may be causeless 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 forepart, rear, and side views are sometimes chosen eleva tions, eastward.thousand., front end elevation. The height view may be termed the plan.
If desired, the rear view may be shown both ways – at the farthermost left or the extreme right. When this is not practical to bear witness rear view at he extreme left or correct due to the length of the office, particularly with panels and mounting plates, the rear view should non be projected upwards or downwards, every bit this would effect in its being shown upside downward.
Instead, it should exist drawn as if projected sideways, but located in another position, and should be clearly labelled REAR VIEW REMOVED.
In first angle orthographic projections the object is considered as existence rolled over to either side, so that the right side of the object is drawn to the left of the front elevation:
It is mandatory to bespeak the method of multiview project by including the appropriate ISO (International Arrangement for Standardization) projection symbol – the truncated cone:
You lot should place this symbol in the lower correct-hand corner of the cartoon in or adjacent to the title block.
Axonometric projection
It is ane of the pictorial drawing projections, which are useful for illustrative purposes, educational aids, installation and maintenance drawings, design sketches, and the like.
The Greek word axon ways axis and metric means to measure. Axonometric projection is a parallel project technique used to create a pictorial drawing of an object past rotating the object on an centrality relative to a airplane of project.
Axonometric projections such equally isometric, dimetric, and trimetric projections are orthographic, in that the project lines are all parallel, but the bending of views is so chosen that iii faces of a rectangular object would be 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 form the corner of the object that is nearest to the observer.
When all three angles are unequal the cartoon is classified equally a trimetric. When two of the three angles are equal the drawing is classified equally a dimetric. When all 3 angles are equal the drawing is classified as a isometric.
Although at that place are an space number of positions that tin can be used to create such a cartoon only few of them are used.
Enlarged particular
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 equally the main view,
- the scale of enlargement must be shown, and
- both views should be identified past 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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