5The Glass BoxImagine that the object you are going to draw is positioned inside a glass box, so that the large flat surfaces of the object are parallel to the walls of the box.From each point on the object, imagine a ray, or projector perpendicular to the wall of the box forming the view of the object on that wall or projection plane.
11Using a Miter Line to Transfer Depth 1.Draw miter line at 45 degreesat a convenient distance to produce the desired view.
12Sketch light lines projecting depth locations for points to miter line and then down into side view as shown.2.
13Project additional points, surface by surface. 3.
144.Draw the view locating each vertex of the surface on the projection and miter line.
15Symbols for 1st & 3rd Angle Projection Third angle projection is usedin the U.S., and Canada
16Other Visualization Tools Number vertices in different views of multiview and isometric drawingPractice
17Multiview SketchingRepresents a 3-D object with a series of 2-D views in contrast to “pictorials” which show all three dimensions in a single viewAlso called orthographic projectionMultiview DrawingPictorial
18Parallel projection Preserves true relationship between features Lines that are parallel on the object are parallel on the drawing
20Projection Planes versus Views Object formed from projection lines projected perpendicularly onto a projection planePlanes: Horizontal, frontal, and profileEach projection plane is perpendicular to adjacent projection planesPrinciple viewsThe object is rotated 90 degrees about the horizontal or vertical axis to give six principle views (top, bottom, front, rear, left, and right side)Common views: top, front, and right side
21Only use Necessary Views One view drawingsSphere (Football)Two view drawingsCylindrical partsShow the circular and rectangular viewThree view drawingsUsually sufficient for all other drawingsTop, front, and right side view
22Orientation and Placement of Views The most descriptive view should be selected as the front viewThe natural orientation of the part should be preserved if possibleViews must be alignedTop view above front viewRight view to the right of front view
23Hidden lines Represented with dashed lines Precedence of lines (visible, hidden, center)Views should be selected to minimize the use of hidden lines most descriptive view should be selected as the front view
24Fold Lines Represents a 90 degree fold between views Generally not shown on engineering drawings except when views other than the principle views (auxiliary views) are used.
25Terminology to Relate Views Adjacent viewA view that is separated by a fold lineThe top view is an adjacent view to the front viewCentral ViewA view that is between two adjacent viewsThe front view is the central view of the top, front, and right side viewRelated viewsTwo views that are adjacent to a central viewThe top and right side view are related views since they are both adjacent to the front view
26Constructing a New View 2The top and front views of a surface are shownThe fold line represents a 90 degree fold between the viewsParallel projection lines are perpendicular to the fold line13132
27Constructing a New View A vertical fold line is drawn at an arbitrary distance from the front viewParallel projection lines are drawn from each vertexThe common depth between the top and side view is used to locate each vertex on the projection lines123
28Sketching Allows for the Quick Translation of Thoughts to Paper Commit thoughts to paper before you lose an ideaAvoid the of use mechanical tools (drawing tools are helpful for beginners)Does not need to be an exact representationobjects may be simplifiedparts may be missingAvoid erasingas new ideas are developed make new sketchesstart with light lines and then darken with darker lead or heavier strokes
29SummaryThe six standard views are often thought of as produced from an unfolded glass box.Distances can be transferred or projected from one view to another.Only the views necessary to fully describe the object should be drawn.