Perpendicular Lines and Planes Engineering Drawing
A iii-dimensional object can be represented in a single plane, such as on a sail of newspaper, using projecting lines and planes. All projection theory is based on 2 variables: line of sight (projecting lines) and airplane of projection.
A line of sight (LOS) is an imaginary line between an observer'south eye and an object. A plane of project (i.e., an epitome or picture plane) is an imaginary apartment plane upon which the image is projected. The projection is produced by connecting the points where the lines of sight pierce the projection plane. As a upshot, the 3D object is transformed into a 2D view.
If the altitude from the observer to the object is space, then the projection lines are assumed to exist parallel, and the projection is called a parallel project. Parallel projection 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.
Yous can employ parallel projection technique to create both multiview and pictorial (isometric and oblique) views.
- In multiview orthographic projection (run into details below), the object surface and the projection plane are parallel, and you can run into only two dimensions.
- In isometric view (orthographic) the surface is no longer parallel to the projection airplane, 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 project aeroplane are also parallel, but the lines of sights are non perpendicular to the projection plane, and yous can see once again iii dimensions.
If the altitude from the observer to the object is finite, then the project lines are not parallel (since all lines of sight start at a single point), and the drawing is classified every bit a perspective projection. In perspective view the object surface and projection plane 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 i face of an object by rotating the object relative to your line of sight helps in understanding the 3D class. Having several views on one drawing y'all utilise the concept of multi-view project, which is based on the orthographic (parallel) projection technique where
- the aeroplane of project is positioned between the observer and the object,
- the plane of project is perpendicular to the parallel lines of sight, and
- the object is oriented such that only two of its dimensions are shown.
Main principles of creating multiview projections
The plane of project tin exist 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 project:
- Front view – the one that shows about features or characteristics.
- Left side view – shows what becomes the left side of the object afterwards establishing the front end view position.
- Right side view – shows what becomes the right side of the object after establishing the forepart view position.
- Meridian view – shows what becomes the height of the object once the position of the front view is established.
- Lesser view – shows what becomes the lesser of the object once the position of the front view is established.
- Rear view – shows what becomes the rear of the object one time the position of the front view is established.
The most informative (descriptive) view of the object to be represented is usually chosen as the principal view (front end view). This is view A related to the corresponding 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 be limited to the minimum necessary to fully represent the object without ambiguity.
Unnecessary repetition of details must be avoided.
Conventional view placement
More often than not, three views of an object are enough, however, a drawing must incorporate equally many views equally necessary to illustrate the part, commonly at right angles to one another.
Frontal airplane of projection
In multiview projection, the object is viewed perpendicular to the master faces, and then that only i face up of the object is depicted in each view. The frontal plane of projection is the airplane onto which the front view of a multiview drawing is projected.
In the front end view you can meet height and width of the object, simply you lot cannot see its depth.
Horizontal airplane of projection
The acme view is projected onto the horizontal plane of projection, which is plane suspended to a higher place and parallel to the elevation of the object.
The top view of an object shows the width and depth dimensions.
Contour aeroplane of project
In multiview drawings, the correct side view is the standard side view. The correct side view is projected onto the right profile aeroplane of projection, which is a plane that is parallel to the correct side of the object. However, you can also use the left side view if it is more descriptive and informative. Moreover, when needed, y'all can include both side views into ane drawing.
The side view of an object shows the depth and height dimensions.
The three-view multiview drawing is the standard used in applied science and technology, because frequently the other iii common views are mirror images and do non add to the noesis near the object.
The standard views used in a three-view drawing are the
- top,
- front, and
- right side views,
arranged as shown in the figure:
The width dimension is common to the front and summit views. The height dimension is common to the forepart and side views. The depth dimension is common to the elevation and side views.
For simple parts ane or two view drawings will often be plenty. In 1-view drawings the third dimension may be expressed past a annotation, or by descriptive words, symbols, or abbreviations, such every bit Ø, HEX, etc.
Square sections may be indicated by light crossed diagonal lines, every bit shown above, which applies whether the face is parallel or inclined to the drawing plane.
Another example of a one-view cartoon:
Additional views may exist added if they improve visualization.
The views should besides be called to avert hidden characteristic lines whenever possible. That means that the most descriptive view should be shown.
As well, 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 so important?
To produce a new product, information technology is necessary to know its truthful dimensions, and true dimensions are not adequately represented in most pictorial drawings. For case, the photograph is a pictorial perspective epitome. However, as y'all can see, 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 electric pole!
In mechanical engineering perspective projections misconstrue measurements.
As y'all can see, the two width dimensions in the front view of the block announced different in length in the perspective project. In other words, equal distances do not appear equal on a perspective cartoon.
Thus, since engineering and engineering depend on exact size and shape descriptions for design, the all-time approach is to use the parallel project technique (orthographic projection) to create multi-view drawings where each view shows only ii of the three dimensions (width, height, depth).
To summarize:
The reward of multiview drawings over pictorial drawings is that multiview drawings shows the truthful size and shape of the various features of the object, whereas pictorials misconstrue true dimensions which are critical in manufacturing and construction.
onest & 3rd angles (drinking glass box)
What exactly you should identify on the correct side projection?
Is it that we can run across from the left side, or from the right side of the object?
To answer these questions in that location are 2 different ways, based on two unlike principles
- Beginning-Angle Projection
- Third-Bending Projection.
Third angle is used in Canada and the United states of america. First angle is used in Europe.
In tertiary angle orthographic projection the object may be assumed to be 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 by the names as shown.
The front, rear, and side views are sometimes chosen eleva tions, east.chiliad., front elevation. The top view may exist termed the plan.
If desired, the rear view may exist shown both ways – at the extreme left or the farthermost right. When this is non practical to show rear view at he extreme left or correct due to the length of the office, specially with panels and mounting plates, the rear view should not be projected upward or down, every bit this would result in its being shown upside down.
Instead, information technology should be drawn as if projected sideways, but located in another position, and should be conspicuously labelled REAR VIEW REMOVED.
In outset bending orthographic projections the object is considered as being rolled over to either side, and so that the right side of the object is drawn to the left of the front peak:
It is mandatory to indicate the method of multiview project past including the advisable ISO (International Organization for Standardization) projection symbol – the truncated cone:
You lot should place this symbol in the lower correct-mitt corner of the drawing in or adjacent to the title block.
Axonometric projection
It is one of the pictorial cartoon projections, which are useful for illustrative purposes, educational aids, installation and maintenance drawings, design sketches, and the like.
The Greek word axon means axis and metric ways to measure. Axonometric projection is a parallel project technique used to create a pictorial drawing of an object by rotating the object on an axis relative to a plane of projection.
Axonometric projections such as isometric, dimetric, and trimetric projections are orthographic, in that the project lines are all parallel, just the bending of views is so chosen that 3 faces of a rectangular object would exist shown in a single view.
Axonometric drawings are classified past the angles between the lines comprising the axonometric axes. The axonometric axes are axes that run across to class the corner of the object that is nearest to the observer.
When all iii angles are diff the drawing is classified as a trimetric. When two of the three angles are equal the cartoon is classified as a dimetric. When all three angles are equal the drawing is classified every bit a isometric.
Although there are an space number of positions that tin be used to create such a drawing 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 mode as the principal view,
- the scale of enlargement must be shown, and
- both views should exist 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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