PROJECTIONS CONICAL PROJECTIONS PARALLEL PROJECTIONS OBLIQUE PROJECTIONS ORTHOGRAPHIC PROJECTIONS ISOMETRIC MULTI-VIEW
an object; The Description of Forms Behind every drawing of an object is space relationship involving four imaginary things: a plane of projection; an observer (the station point); projectors lines of sight.
Conical projections In this type of drawing, the observer is relatively close to the projection plane. The lines of vision thus form a cone directed towards the observer s eye.
In conical projections, the edges which are closer to an observer, are larger compared to the edges which are farther When drawing conical projections, use at least 2 vanishing points
The visual rays are perpendicular to the projection plane, so the projection is said to be orthographic (orthogonal) Orthographic parallel projections
Multi-view orthographic projections TOP VIEW Here is the usual representation of views in multi-view orthographic projections. This type of drawing is used in technology because it allows description without deforming the faces of objects. FRONT VIEW RIGHT SIDE VIEW
Top view Front view, and Right Side view are three commonly used views in multiview projection
Multi-view orthographic projections are a part of parallel projections. In this type of drawing, the observer is considered to be at an infinite distance. The projecting lines are parallel to one another. Multi-view orthographic projections These projections are also orthographic since both the observer and the object are perpendicular to the projection plane.
Multi-view orthographic projections Another distinguishing element in multi-view projections is that one of the faces of the object to be drawn is placed parallel to the projection plane. The observer can only see one side at a time. That is why, in most cases, one must draw several views of the object to portray it completely.
Multi-view orthographic projections In technical drawing, the views are flat figures (two dimensions) that we see from directly in front of each object. Height Width
Multi-view orthographic projections In the type of projections used in North America, we imagine the object being drawn in the center of a transparent box. The different views of the object are projected onto the sides of this box.
Multi-view orthographic projections One of these views is designated as the front view of the object. We usually choose the face that best portrays the object. The choice of the front view determines the placement of the other views.
ISOMETRIC Drawings In Isometric projection : 1) all three dimensions can be seen in one view 2) the intersecting edges of the object are on the axes that are spread at 1. This way the angles between all intersecting edges are either 1 or 60.
Isometric projections A cube shown with this type of projection pivots 45º to show three faces on the projection plane instead of a single face. It is then tilted frontward or backward, allowing three faces to be observed.
The observer is still at infinite distance, the projecting lines remain parallel to one another, but the object is placed so that the lines of vision are oblique (not perpendicular) to the projection plane. Oblique parallel projections
OBLIQUE projections are unnatural projections, because the angles and lengths of edges are wrong. It is impossible to actually see objects in this way
SUMMARY CONVENTIONAL LINES LINE NAME PURPOSE THICKNESS A Object line or visible outline Portrays visible forms. Thick 100 % B Hidden feature line Portrays surfaces and edges that are hidden from view Medium 50 % C Center line Portrays the center of a round or circular object. Fine 25 % D Extension line Is used to indicate the dimension. Fine E Dimension line Is used to indicate the dimension. Fine F Cutting plane line Indicates the placement of an imaginary cut. Very thick G Section lines Indicate the surface imagined to have been cut. Fine H Break line Used to shorten the view of a part. Fine J Leader Indicates the part of a drawing to which a note refers Fine
CONVENTIONAL LINES 8 - FACING LAMAGE 14 X 3 PROF. DEEP 13 50 In a technical drawing, each type of line has its own significance. Each is distinguished from the other by a particular thickness or shape. 40 45 45 24 The object above is drawn in isometric projection. It is portrayed on the left by three views. We will use this object to illustrate the principal lines found in technical drawing on the slides which follow. 80
CONVENTIONAL LINES A OBJECT LINE OR VISIBLE OUTLINE
CONVENTIONAL LINES The object line or visible outline is made of a continuous line that portrays the visible forms of the object. It is a thick line, its thickness chosen to clearly show the shape. OBJECT LINE OR VISIBLE OUTLINE
CONVENTIONAL LINES B B HIDDEN FEATURE LINE
CONVENTIONAL LINES The hidden feature line is made of a dashed line that portrays surfaces and edges that are hidden from view. The line is medium sized, half the width of the one chosen for the visible outline. B HIDDEN FEATURE LINE
CONVENTIONAL LINES C C THE CENTER LINE
CONVENTIONAL LINES The center line is made from phantom lines. It is used to designate the axes of circular or cylindrical shaped objects. The line is half the width of the one used for hidden features. It is a fine line. THE CENTER LINE
CONVENTIONAL LINES D DIMENSION LINE
CONVENTIONAL LINES The dimension line is a fine line ending with an arrow. The purpose of these lines is to provide dimensions. DIMENSION LINE DIMENSION LINE
CONVENTIONAL LINES The dimension is a value used to indicate size in a technical drawing. 40 40 This value is given in millimetres. 45 80 DIMENSION
CONVENTIONAL LINES 50 40 13 24 40 45 E 80 EXTENSION LINE
CONVENTIONAL LINES 50 Extension lines are fine lines that indicate the placement of the dimensions. 40 13 24 40 45 80 EXTENSION LINE
CONVENTIONAL LINES 50 Ø 8 FACING Ø14 x 3 DEEP F 40 13 24 40 45 80 THE LEADER
CONVENTIONAL LINES Ø 8 FACING Ø14 x 3 DEEP 40 13 The leader is used to indicate the part of 50the drawing to which a comment refers. 24 40 45 80 THE LEADER
CONVENTIONAL LINES 50 G Ø 8 FACING Ø14 x 3 DEEP 40 13 24 40 45 80 CUTTING PLANE LINE
CONVENTIONAL LINES Ø 8 FACING Ø14 x 3 DEEP 40 13 50 The cutting plane line is very thick; this line is used to designate where an imaginary cut took place. 24 40 45 80 CUTTING PLANE LINE INFORMATION ON CUTS
TOP VIEW The section view allows one to see inside the object. It makes the object simpler to understand by eliminating hidden feature lines. The cutting plane line show where the object is cut. The arrows indicate the point of view of the observer. Section lines emphasise which part has been cut in the section view. We presume that the part between the cutting plane line and the observer has been removed. The section is drawn in a view adjacent to the cutting plane line. SUMMARY
CONVENTIONAL LINES 50 Ø 8 FACING Ø14 x 3 DEEP 40 13 24 40 H 45 80 SECTION LINES
CONVENTIONAL LINES 50 Section lines are fine lines used to indicate the surface imagined to have been cut. Ø 8 FACING Ø14 x 3 DEEP 40 13 24 40 45 80 SECTION LINES
CONVENTIONAL LINES 50 Ø 8 FACING Ø14 x 3 DEEP 40 13 24 H 40 45 80 THE SHORT BREAK LINE H
CONVENTIONAL LINES Ø 8 FACING Ø14 x 3 DEEP The short break line is a thick, irregular line used to indicate a partial cut. This line is drawn freehand. 40 13 50 24 40 45 80 THE SHORT BREAK LINE
THE LONG BREAK LINE The long break line is a fine line used to shorten the view of a long part that can not be shown full length.
SUMMARY CONVENTIONAL LINES LINE NAME PURPOSE THICKNESS A Object line or visible outline Portrays visible forms. Thick 100 % B Hidden feature line Portrays surfaces and edges that are hidden from view Medium 50 % C Center line Portrays the center of a round or circular object. Fine 25 % D Extension line Is used to indicate the dimension. Fine E Dimension line Is used to indicate the dimension. Fine F Cutting plane line Indicates the placement of an imaginary cut. Very thick G Section lines Indicate the surface imagined to have been cut. Fine H Break line Used to shorten the view of a part. Fine J Leader Indicates the part of a drawing to which a note refers Fine