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TECHNICAL SKETCHING - PowerPoint PPT Presentation

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TECHNICAL SKETCHING. Drafting. The Universal Language Drafting is the process of accurately representing three-dimensional objects and structures on a two-dimensional surface, usually paper. An accurate drawing process used for nearly every product or structure made today – large or small.

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  • The Universal Language
  • Drafting is the process of accurately representing three-dimensional objects and structures on a two-dimensional surface, usually paper.
  • An accurate drawing process used for nearly every product or structure made today – large or small.
  • Drawings are also used to communicate ideas effectively and accurately.
  • Rough Sketches are the most common recording method. The term “rough” describes the state of the design ideas. It suggests that the designs are incomplete and unrefined.
  • Refined Sketches are refined design ideas. They may not look anything like the original rough sketches.
  • Detailed Sketches communicate size, in addition to the shape and proportion communicated in the first two drawings. It also communicates the information needed to build a model of the product or structure.

Pictorial Sketches

Different techniques are used to show the artifact as the human eye would see it. Therefore, a single view is used to show how the front, sides, and top would appear.

Perspective Sketches

Oblique Sketches

Isometric Sketches

pictorial drawings
Pictorial Drawings

Pictorial drawings show several sides at the same time.  Many people find pictorial drawings easier to understand.  They do not provide as much information as orthographic views.


Oblique Sketches

  • The easiest pictorial sketches to produce.
  • Show the front view as if you were looking straight at it.
  • Sides extend back from the front view.
  • Sides shown with parallel lines that are generally drawn at 45 degrees to the front view.

Oblique Sketches

  • Cavalier Oblique drawings cause the sides and top to look deeper than they are.
  • Cabinet Oblique drawings shorten the lines that project back from the front to one-half their original length.
isometric sketches
Isometric Sketches

Isometric means equal measure.

Angles formed by the lines at the upper right corner are equal to 120 degrees.

Object is shown as if viewed from one corner.


Perspective Sketches

  • Show how the human eye and camera would see it.
  • Realism is obtained by having parallel lines meet at a distance vantage point.
  • Most realistic, yet, most difficult of the three sketches.

Types Of Perspective

  • Three major types: one-point, two-point, and three-point.
  • One-point perspective shows an object as if you were directly in front of it.
  • Two-point perspective shows how an object would appear if you stood at one corner.
  • Three-point perspective shows how the eye sees the length, width and height of an object.
detail drawings
Detail Drawings
  • Most are prepared using the multi-view method.
  • This method places one or more views of the object in one drawing.
  • Generally, a top, right side, and end view are shown.
  • Multi-view drawings use orthographic projection to project information at the right angles to new views.
  • Front view is drawn in the lower left quadrant of the paper.
  • Projection lines are extended to the top and right of a front view to form the top and side views.
orthographic drawings
Orthographic Drawings
  • Orthographic views are two-dimensional drawings used to represent or describe a three-dimensional object. The ortho views represent the exact shape of an object seen from one side at a time as you are looking perpendicularly to it without showing any depth to the object
orthographic drawings21
Orthographic Drawings
  • Primarily, three orthographic views (top, front, and right) adequately depict the necessary information to illustrate the object.

Drawing Lines

Different lines are used to show the outlines and major details on an object.

Object lines are the darkest lines which show the outlines and major details.

Hidden lines are dotted lines used to show outlines which are not visible in a certain view.

Center lines locate holes in a part. These lines pass through the center of the hole.

Extension lines, used in dimensioning, indicate the points from which the measurements are taken.

Between the extension lines are the dimension lines. These have arrows pointing to the extension lines that indicate the range of the dimension.

computer aided drafting
Computer Aided Drafting
  • CAD is used in every drafting discipline.
    • Mechanical Engineering
    • Architectural Engineering
    • Construction
    • Electrical Engineering
  • 2 Dimensional
    • AutoCAD
    • CADD
  • 3 Dimensional
    • Solid Works
    • 3D Studio
computer aided drafting25
Computer Aided Drafting
  • CAD (Computer-Aided Design) refers to a process that uses a computer and drawing software to assist the drafter in preparing mechanical or architectural drawings. CADD (Computer-Aided Design and Drafting) is closely related to CAD.
  • CADD systems use extra functions that simulate testing products. Professional designers use CADD to increase the quality of their work.
cartesian coordinate system
Cartesian Coordinate System
  • A method of graphical point location.
  • All CAD systems use this system as a standard.
  • It allows precise positioning of entities on the drawing surface.
computer aided drafting27
Computer Aided Drafting
  • The graphic primitives are defined geometrically in terms of the normal Cartesian Coordinate System (right-handed system with positive X-axis to the right, positive Y-axis up the screen and positive Z-axis coming out of the screen towards the user).
computer aided drafting28
Computer Aided Drafting
  • Advantages of CAD - The heart of a CAD system is the computer. A computer is capable of producing drawings much faster than humans. Computers can be programmed to perform certain complex functions with just the push of a single key. A traditional drafter may have to complete dozens of pencil strokes to perform the same function. Computers are generally more accurate than humans, and they can perform the same function over and over without errors or deviations. CAD has several advantages over traditional drafting methods.
  • Four advantages of CAD are: speed, quality, ease of modification, and cost.
cad terminology
CAD Terminology
  • Commands- short words which, when entered, causes the computer to perform some function.
  • Entity-an object or text item created using CAD software.
  • Grids-help the drafter easily locate position on the drawing. They are used like lines on graph paper. The grid assists the drafter in drawing entities. Most programs allow the drafter to adjust the spacing of the dots. This is referred to as grid spacing.
  • Snap Grids-is used to lock the drawing cursor to grid points as it is moved across the screen. When snap grid is on, the cursor jumps from grid point to grid point as it moves across the screen.
cad terminology30
CAD Terminology
  • Rotation-used to rotate an entity around a base point.
  • Zoom-allows the drafter to move in on a particular part of a drawing. By moving in on the drawing, the drafter can view more details. This function is extremely useful when working with very detailed drawings.
  • Windows- most CAD programs allow the screen to be split into separate windows. Each window is a separate display screen. The windows function is useful when working on very large drawings.