Unit 3: C.A.D.

  • Unit 3: C.A.D.



    Drafting refers to all the drawing techniques that are used to describe the size, shape, and structure of objects.

    A Technical drawing, or mechanical drawing, uses mechanical or electronic tools to accurately show the size and shape of objects.

    A scale drawing shows an object’s actual shape drawn smaller or larger than its actual size.

    If you were to draw, rather than photograph, these different views of the object, you would have a multi-view drawing

    Dimensions give the size of the object and the exact size and location of holes, cutouts, and other features.

    A pictorial drawing, which is a realistic-looking drawing of a three-dimensional [3D] object.

    In an isometric drawing, the object being drawn is rotated 30 degrees and tilted forward 30 degrees so three sides are shown.

    In oblique drawings you can see a perfect undistorted front view of the object that is combined with a distorted angle view of the other two sides.

    In a perspective drawing, the object appears as it would in real life.

    Drawings that show the inside of an object are called section drawings.

    The use of computers to do design and drafting is known as CAD


     Orthographic: The word orthographic as used in geometry refers to right angles and perpendicular lines [90 degrees].

    Projection: Projection means to represent something on a plane much like a movie is projected onto a screen.

    Orthographic Projection: Orthographic Projection is a method of representing the exact shape of an object by projecting lines onto a plane of vision. Three planes are usually projected to give an accurate presentation of the top, front and side.

    Object Lines: Object lines are solid lines (drawn dark) representing the contour (shape) of an object as we see it.

    Extension Lines: Extension lines are lines that are drawn lightly between views that transfer the proper proportions.


    Equal: Constrains selected circles and arcs to the same radius and selected lines to the same length.

    Vertical Constraint: Causes lines, ellipse axes, or pairs of points to lie parallel to the Y axis of the sketch coordinate system.

    Horizontal Constraint: Causes lines, ellipse axes, or pairs of points to lie parallel to the X axis of the sketch coordinate system.

    Perpendicular Constraint: Causes selected linear geometry to lie at right angles to each other.

    Parallel Constraint: Causes selected linear geometry to lie parallel to each other.

    Tangent: Constrains curves, including ends of a spline, to be tangent to other curves.

    Concentric Constraint: Causes two arcs, circles, or ellipses to have the same center point.


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