SDC PUBLICATIONS © 2012 Chapter 6 Pictorials and Sketching Objectives: Understand the importance...

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Chapter 6 Pictorials and Sketching

Objectives: Understand the importance of Freehand

Sketching. Understand the terminology used in Pictorial

drawings. Understand the Basics of the following

projection Methods: Axnonometric, Oblique and Perspective.

Be able to Create Freehand 3D Pictorials.

Tools For Design:AutoCAD® & Autodesk Inventor

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Engineering Drawings, Pictorials and Sketching

Engineering design is a process to create and transform ideas and concepts into a product definition that meet the desired objective. The engineering design process typically involves three stages: (1) Ideation/conceptual design stage: this is the beginning of a engineering design process, where basic ideas and concepts take shapes. (2) design development stage: the basic ideas are elaborated and further developed. During this stage, prototypes and testing are commonly used to ensure the developed design meet the desired objective. (3) Refine and finalize design stage: This stage of the design process is the last stage of the design process, where the finer details of the design is further refined. Detailed information of the finalized design are documented to assure the design is ready for production.

Two types of drawings are generally associated with the three stages of the engineering process: (1) Freehand Sketches and (2) Detailed Engineering Drawings.


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Freehand Sketches are generally used in the beginning stages of a design process: (1) To quickly record designer’s ideas and help formulating different possibilities, (2) To communicate the designer’s basic ideas with others and (3) To develop and elaborate further the designer’s ideas/concepts.

During the initial design stage, an engineer will generally picture the ideas in his/her head as three-dimensional images. The ability to think visually, specifically three-dimensional visualization, is one of the most essential skills for an engineer/designer. And freehand sketching is considered as one of the most powerful method to help develop visualization skills.

Detailed engineering drawings are generally created during the second and third stages of a design process. The detailed engineering drawings are used to help refine and finalize the design and also to document the finalized design for production. Engineering drawings typically require the use of drawing instruments, from compasses to computers, to bring precision to the drawings.


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PictorialsBesides the 2D orthographic views, described in the previous chapter, there are three main divisions commonly used in freehand engineering sketches and detailed engineering drawings: (1) Axonometric, with its divisions into isometric, dimetric and trimetric; (2) Oblique and (3) Perspective.


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Axonometric ProjectionThe word Axonometric means “to measure along axes". Axonometric projection is a special orthographic projection technique used to generate pictorials. Pictorials show a 2D image of an object as viewed from a direction that reveals three directions of space. There are three types of axonometric projections: isometric projection, dimetric projection, and trimetric projection. Typically in a axonometric drawing, one axis is drawn vertically.

IsometricIsometric DimetricDimetric TrimetricTrimetric


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Oblique ProjectionOblique Projection represent a simple technique of keeping the front face of a object parallel to the projection plane and still reveals three directions of space. An orthographic projection is a parallel projection in which the projection lines are perpendicular to the plane of projection. An oblique projection is one in which the projection lines are other than perpendicular to the plane of projection. In an oblique drawing, geometry that are parallel to the frontal plane of projection are drawn true size and shape.

OrthographicProjection

OrthographicProjection

ObliqueProjectionOblique

Projection


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Perspective Projection

Perspective Projection adds realism to the three-dimensional pictorial representation; a perspective drawing represents an object as it appears to an observer; objects that are closer to the observer will appear larger to the observer. The key to the perspective projection is that parallel edges converge to a single point, known as the vanishing point.

One-PointPerspectiveOne-Point

Perspective

Two-PointPerspectiveTwo-Point

Perspective

Three-PointPerspectiveThree-PointPerspective

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