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Axonometric Drawings. Isometric Drawing and Sketching. Content. • Overview – Axonometric projection • Isometric projection – Axes and selection – Isometric lines and planes – Isometric projection & Isometric drawing • Producing Isometric sketches & drawing
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Axonometric Drawings Isometric Drawing and Sketching
Content • Overview – Axonometric projection • Isometric projection – Axes and selection – Isometric lines and planes – Isometric projection & Isometric drawing • Producing Isometric sketches & drawing – Isometric lines & non-isometric lines – Circles and arcs – Irregular curves
Pictorials • Pictorial drawings which include Axonometric, oblique and perspective projections are pseudo 3-D drawings. Drawn in 2-D. Looks 3-D.
Pictorials are often used to help the print reader visualize the part.
Fig. 9.43 Courtesy of Alventive, Inc.
Fig. 9.44 Courtesy of Alventive, Inc.
Pictorials in Mechanical Engineering • The two most common types of pictorials in Mechanical Engineering discipline are: • Isometric • Oblique
Pictorial projection – Not intended to give exact or true view. – Not intended to transmit dimensions, although sometimes dimension is useful. – Useful when the information and instructions to be given to non-technical and untrained people. – Hidden lines are not shown in isometric drawing.
AxonometricProjection • axon= axis; metric= measure, in Greek • Axonometric projection is a parallel projection technique to create a pictorial drawing of an object by rotating the object on an axis relative to a projection or picture plane.
Projection Isometric : Axes • The 3 axis meet at A,B form equal angles of 120 deg and they are called Isometric Axes. • OA is vertical, OB is inclined at 30deg to the right, OC is inclined at 30deg to the left.
Isometric Pictorial Axes • Isometric pictorials are drawn in a coordinate system where the axes are 60 degrees apart.
Contents Isometric projection vs. Isometric sketch
a a 0.8a 0.8a a 0.8a Isometric projection The projected lengths of the edges parallel to the axonometric axes are approximately 81% of theirtrue length. 3-D object (Cube) Axonometric projection Isometric view 45 35o16'
Isometric sketch Isometric sketch has a similar shape as an isometric projection view except that their edges parallel to the axonometric axes are drawn in full size. Isometric sketching/drawing Isometric projection Foreshorten Full size
Isometric axes C D B A Angle & distance in isometric sketch Angles in an isometric sketch distort from the actual angle found in the object. Actual or true distance can be measured along the isometric linesof the isometric sketch. Example 90o angle appears as 120o. Correct 90o angle appears as 60o. Wrong
Selection of Isometric Axes • Main purpose of isometric view is to provide a pictorial view which reveals as much detail as possible • Selection of principal edges is important • Figure shows different isometric views of the same block
Standards in Isometric Drawing • Hidden Lines - must be omitted unless absolutely necessary to completely describe the object. Avoid using hidden lines. • Centre Lines - do not show centre lines. Use only for showing symmetry or for dimensioning. Isometric drawings are used to communicate to non-technical people and not for engineering purposes. • Dimension - do not show dimensions if it is not for production purposes. Dimensioned isometric drawings used for engineering purposes must follow standards such as ANSI, MS, BS, ISO, DIN, JIS etc.
Dimensioning Isometric Drawing Unidirectional - production purposes Aligned Method - illustration purposes
Constructing Isometric Drawing Boxing-in method Step 1 Determine the desired view of the object; then draw the isometric axes Step 2 Construct the front isometric plane using width W and height H dimensions Step 3 Construct the top isometric plane using width W and depth D dimensions Step 4 Construct the right side isometric plane using depth D and height H dimensions Step 5 Transfer some distances for the various features from the multiview drawing to the isometric lines that make up the isometric rectangle. Begin drawing details of the block by drawing isometric lines between the points transfer from the multiview drawing. Step 6 Transfer the remaining features from the multiview drawing to the isometric drawing. Step 7 Darken all visible lines, and erase all construction lines to complete the isometric drawing of the object.
Producing Isometric drawing • Read the orthogonal drawing (multiview) carefully, determine front, side & top view. • Observe scale, dimension, projection angle, • choose the best point where isometric axes meet to reveal as much detail as possible • Try to visualize how the object looks like, you can label points, lines and surfaces on multiview to help visualization. • If not sure, start with sketching an isometric box, enclosing the whole object. • Draw an 'isometric box' enclosing the object, draw in light construction lines • Draw in thick solid lines, arcs & curves, remove excess. • line in 30° right lines • line in 30° left lines • line in vertical lines to complete the view
Producing Isometric drawing Given an example of a orthogonal drawing (multiview)
Producing Isometric drawing • You can start drawing, once you’re able to visualize how the object looks like, or finish sketching. • Start with drawing construction line – draw the iso-box, and fill up with other lines. • Line in (darken) arcs & circles. • Line in iso-lines. • Line in all other lines.
Isometric Drawing Drawing Linear Features
Drawing Linear Features • How do we draw an isometric pictorial?
Drawing Linear Features Step 1) Draw the three construction lines that represent the isometric axes.
Drawing Linear Features Step 2) Draw a defining box. • Sides = maximum height, width and depth dimensions of the object.
Drawing Linear Features Defining Box
Drawing Linear Features Step 3) Draw the lines of the object that are parallel to the axes.
Drawing Linear Features Step 4) Add the lines of the object that are not parallel to one of the axes.
Drawing Linear Features Step 5) Erase or remove the construction lines. Note: If the drawing is produced using CAD software in a 2-D isometric drawing, it should be scaled by 80%.
Example Exercise 1 Creating an Isometric Drawing with Linear Features
Exercise 1 • Create a full scale isometric drawing of the following object. (Use a pencil.)
Step 1) Draw three construction lines that represent the isometric axes. (Done) The grid spacing is 0.5 inch.
Step 2) Draw a box whose sides are parallel to the three axes and whose lengths are ½ the maximum height, width and depth dimension of the object.
Step 3) Draw the lines of the object that are parallel to the axes.
Step 4) The lines of the object that are not parallel to one of the axes are added by connecting the ends of existing lines.
Drawing Circles and Radii • Circular features of an object appear as ellipses on an isometric pictorial.
Iso-circles and arcs • Isometric circles or iso-circle cannot be simply drawn using compass. • Any iso-circle may lie on either top plane, left (front) plane or right (profile) plane. • Iso-circle looks slightly oval and skewed.
Drawing iso-circles (a) Draw centre lines, vertical & 30deg to left. (b) Draw (construction line) 20mm “square box”. The centre lines should divide each side by half. (c) Draw straight lines; 1-2 & 1-3 and 2-5 & 2-6. (d) Point 7 is the intersection between line 1-2 & 4-5, and similarly point 8, 1-3 & 4-6 on the other side. (e) Set your compass to the distance 7-2, draw an arc with centre at point 7, from point 2 to point 5. Do the same on the other side. (f) Set your compass to the distance 1-2, draw an arc with centre (1), from (2) to (3).
Drawing Circles and Radii Step 1) Draw the linear features of the object using the procedure previously described.
Drawing Circles and Radii Step 2) Draw a box whose diagonals meet at the center of the circle and the length of the sides are equal to the circle’s diameter.
