How to draw axonometric diagrams in CAD

Thread Content

An axonometric diagram is a two-dimensional representation that shows the three-dimensional shape of an object; it possesses a sense of depth and helps people understand the structure of a product more quickly and clearly. Creating an axonometric drawing of a part is done in a two-dimensional plane, which is simpler and more convenient compared to three-dimensional representations. The axonometric projection of a solid shows only three visible planes. For the purpose of easier drawing, we use these three planes as reference planes for tasks such as drawing lines and locating points; they are known as axonometric planes. Depending on their position, they are referred to as the left axonometric plane, the right axonometric plane, and the top axonometric plane. Once axonometric mode is activated, it is possible to switch between these three faces separately. For a rectangular prism, the angles between its visible edges and the horizontal line in an axonometric diagram are 30°, 90°, and 120° respectively. I. Activating the axonometric projection mode 1. Method 1: Tools --> Sketch Settings, Snapping, and Grid --> Snapping Types and Styles: Isometric Snapping --> OK to activate it. 2. At the command prompt, enter: snap –> Style: s –> Isometric: i –> Enter vertical spacing: 1 –> Activation is complete. 3. Method for switching isometric views: Use F5 or CTRL+E to switch between the top, right, and left views in sequence. II. Drawing lines in axonometric projection mode: 1. Method for entering coordinate points: For a line parallel to the X-axis, the polar angle should be set to 30°; for example, @50 means 10 units in the horizontal direction – 10 units in the vertical direction – 10 units in the opposite horizontal direction – then C to close the line. 3. F5: Switch to the top view – specify one of the corner points of the top edge – 10 units in the X direction – 10 units in the Y direction – 10 units in the X direction again – then C to close the line. 4. F5: Switch to the right view – specify one of the corner points of the bottom edge – 10 units in the horizontal direction – 10 units in the upward vertical direction – then confirm to complete the operation. III. Locating entities in an axonometric diagram: To locate other known elements within an axonometric diagram, it is necessary to enable the angle increment in automatic tracking and set the angle to 30 degrees; this allows tracking from a known object at angles of 30°, 90°, or 150°. 1. To create a square with a length of 4 to the right of the square in the example above: Capture the lower left corner on the right side –> 3 units in the X-direction –> 4 units in the vertical direction –> 4 units in the horizontal direction –> 4 units in the downward vertical direction –> C to close the shape. 2. To draw a circle with a diameter of 4 on the top surface: Press F5 to switch to the top surface –> use the ellipse tool –> select the isometric circle option –> i –> capture the intersection point of the diagonals –> set the radius to 2 –> confirm to complete the task. IV. Drawing parallel lines within an isometric plane: It is not possible to use the OFFSET command to draw parallel lines within an isometric plane, as the offset distance specified in OFFSET refers to the vertical distance between two lines, whereas the distance along a 30° direction is not equal to the vertical distance. To avoid errors in manipulation, when drawing parallel lines within an axonometric plane, we generally use the COPY command or the “T” option in OFFSET ； It is also possible to use automatic capture, automatic tracking, and orthogonal mode for drawing, which ensures that the drawn lines are aligned with the directions of the axonometric axes. . V. Axonometric projection of a circle: The axonometric projection of a circle is an ellipse; when the circle is located on different axonometric planes, the positions of the major and minor axes of the resulting ellipse vary. Operation method: Activate axonometry --> Select the plane on which the circle will be drawn --> Ellipse tool --> Isometric circle: i --> Specify the center --> Specify the radius --> Confirm to complete. Note: Before drawing a circle, be sure to use the face conversion tool to switch to the axonometric face corresponding to the plane in which the circle lies; only then can an ellipse appear as if it is within that axonometric face, otherwise it will not be displayed correctly. In axonometric drawings, it is often necessary to create smooth transitions between lines, such as rounding corners; in such cases, the transition arcs also need to become elliptical arcs. The method is: draw a complete ellipse in the appropriate position, then use the trimming tool to remove the excess line segments, as shown in Figures 1 to 3 below. VI. Writing text in axonometric drawings: In order for the text within a particular axonometric plane to appear as if it is part of that plane, the text must be tilted at a certain angle depending on the characteristics of that plane’s orientation, so that its appearance matches that of the axonometric drawing; otherwise, the three-dimensional effect will be weak. 1. Text tilt angle setting: Format --> Text Style --> Tilt Angle --> Apply | Off. Note: The best approach is to create two new text styles with tilt angles of 30° and -30° respectively. 2. The inclination rule for each text on the axonometric views is as follows: a. On the left axonometric view, the text must have an inclination angle of -30°, along with a rotation of -30° as well. b. On the right axonometric plane, the text should be tilted at 30° and rotated by 30° as well. c. On the top axonometric plane, when parallel to the X-axis, the text should have an inclination angle of -30°, with a rotation angle of 30° ； When parallel to the Y-axis, a tilt angle of 30° is required, with a rotation angle of -30. Note: The inclination angle of text and the rotation angle of text are two different concepts. The former refers to the angle at which the text is tilted to the left (within the range of 0–-90°) or to the right (within the range of 0–90°), while the latter denotes rotation around the starting point of the text within a range of 0–360°, that is, rotation within the axial plane where the text is located. VII. Dimension marking: To make the dimension markings within a certain axonometric plane appear to be within that plane, it is necessary to tilt the dimension lines and extension lines at an appropriate angle so that they are parallel to the corresponding axes. At the same time, the labeled text must also be set at an inclined angle in order to give the text a three-dimensional appearance.