Question

4th Question:   From you opinion: search and support your answers with drawing for the following questions:
a- What is the meaning of engineering drawing I for future engineers, and why?
b- What are the methods that can use for draw the engineering drawing?
c- What is the difference between isometric and oblique?
d- What types of the projection drawing?

Answer 1

(a) . Answer :

Engineering drawing :

  An engineering drawing is a type of technical drawing used to define the reuirements for engineering products or components. Typically the purpose of an engineering drawing is to clearly and accurately capture all geometric features of a product or component so that a manufacture or engineer can produce the required item. It may also describe the process of making the item, may be used to convey engineering idea during the design process or may provide a record of an existing item. An engineeringdrawing is intended to describe the size and shape of an item and may provide information regarding acceptable variations,load limits,material and any other information that can help give a complete understanding of an item.

  Drawing can be created in oblique and isometric as well as 1^st and 3^rd projection. It is usual for engineering drawings to include a series of projections showing different angles of the item, as well as sections, "exploded"  views and so on. Projections may create two dimensional or three dimensional representations of the item. Engineering drawings are prepared using computers that can also create files used to instruct machines how to manufacture the item.

Technical drawings are the fundamental language of communication in engineering. It has been developed over many years to physically document their work, and engineers must be able to both read and write it to work in engineering design. Drawings are the only way to show the shape, details and all the dimensions of a part, assembly or structure. Previous days this could only be done by pencil on paper, now creating and communicating any kind of design is done by CAD (Computer-Aided Design). This allows the designer to easily create many alternatives, which can then be viewed as 2D drawings or 3D models. With a 3D model we can quickly create 2D views with dimensions according to established rules and standards. Also, we can see the shape of a part in 3D it makes it easy to visualize the 2D views. Both are essential to mechanical engineering. Good knowledge of CAD and engineering drawing is often the first thing an employer checks before making a job offer.

(C) Answer :

Differene between isometric and oblique :

Isometric drawings :

Isometric drawings are a pictorial representation of an object in which all three dimensions are drawn at a full scale. An isometric drawing looks like an isometric projection but all its lines are parallel to the three major axes. These types of drawings are used by engineers to represent all three dimensions of an object on a paper. The horizontal edges are drawn at an angle (usually 30°) from the normal horizontal axes, and the vertical edges, which are parallel to the principal axes, appear in their true proportions. Isometric Sketch focuses on the edge of an object.

Oblique drawings :

  Oblique drawings show a three dimensional view of an object. The width of the object is drawn as a horizontal line, but the depth can be drawn back at any angle. An oblique sketch has a more focus on the front side of an object or the face. It is drawn usually using the 45-degrees angle to render the third dimensions. There are three types of obliques.

1. Cavalier
2. Normal
3. Cabinet

(d) Answer :

Types of the projection drawing :

There are mainely four types of projection drawing :

• Orthographic projection
• Axonometric projection
• Oblique projection
• Perspective projection

Orthographic projection : Orthographic projection shows a 3D object in two dimensions so that we can see three views: the front view, side view and top view. It is usually positioned relative to the rules of first-angle or third-angle projection. The difference between the two is the view. An orthographic projection can also include a section view, which is when a portion of the object is cross sectioned along the specified plane, and the information about that section is displayed. It’s used to show internal specifications.

Axonometric projection :  Axonometric is another type of orthographic projection. It is considered complex because only one image is drawn on the paper’s plane. There are three types of classifications. The most common is isometric, where the angles between the three axes are equal. The second is diametric. Only two of the angles between the axes are equal in this type. Trimetric is the third type. It can have three axes with different angles between them. It is the most common type. Axonometric projection is good for rectangular or square objects rather than objects with curved lines.

Oblique projection : Oblique is a simple type of projection that only requires one image. It can be drawn with traditional tools because it’s not complex. It depicts a 2D image of a 3D object. The object is drawn from the front view, and then the other areas are added in relation to it. It can be divided into two types based on the scaling of the object: cavalier projection, which uses a 1:1 scale, and cabinet projection, which uses a 2:1 scale. It uses parallel lines to produce the source of the object in the image.

Perspective projection : Perspective projection is not based on parallel lines. It is an approximate representation of the object as it would be seen by the eye in respect to depth perception. The projection lines emerge from a single point, showing the closer part larger than the more distant part. The object can feel more realistic with this projection, but it does require a good imagination.