Isometric and orthographic projection drawings tutorial.
Step-by-step lesson in how to map out a simple isometric drawing from plan and elevation views.
All Tutorial Text & Images - Copyright © 2011 KHI, Inc.
An "orthographic" view of an object is simply a single view of that object from a 2-dimensional flat "plan" (overhead) or "elevation" (profile) view. Orthographic projection (aka "orthogonal projection") is a means of representing the 3-dimensional object in only two dimensions. An isometric (Greek for "equal measure") drawing is a form of axonometric projection with the viewer seeing all three axes (width, depth, height) equally foreshortened. Parallel projections have lines of projection that are parallel to each-other within the projection plane.
This type of technical drawing would typically be used to create assembly drawings and "breakaway," or "exploded diagrams," and other technical drawings which are well-suited for assembly and repair manuals or patent application diagrams.
Creating an isometric drawing
The first step will be to draw a base line as a horizontal reference point and a second line which we will rotate using Object>Transform>Rotate shown in Fig 1. You can also use the 'Shear Tool' by going to Object>Transform>Shear and entering in a 'Shear Angle' of 60° or -60° with an Axis set at Horizontal.
To create a grid you would first draw a line using the pen tool and constrain it vertically by holding the Shift key. Then we will clone the vertical line by using the Option>Command keys to duplicate it while clicking the increment key, then using the increment key to move it an equal number of spaces each time we duplicate it. Once we have a series of evenly-spaced lines we will group them together using Command>G then we will duplicate the grouping and flop it horizontally as shown in Fig 4.
The objective is to transform each of the three orthographic views in Fig 5 to look like the three views in Fig 6. To accomplish this we are going to utilize the Shear Tool. We start by placing the flat plane elevation views of our object onto the ground reference line. Then we select the left side elevation of the object and go to Object>Transform>Shear to shear it 30° (Fig 7) then rotate it by -30° to its final position Fig 8. Next we select the right face of the object (Fig 9) and shear it by 30º, then rotate it by 30° to complete the first series of steps.
Next we will distort the top view (plan view) of our object in to the isometric framework grid by first shearing it 30° then rotating it by -30° and aligning it with our left and right sides as shown in Fig 10 below. Then move the top view into the correct position as shown in Fig 11 below.
Now we are ready to begin the process of projecting the remaining lines into the correct positions using our three orthographic views (left, right, top) as a guide. Use the Scissors Tool to cut any corner anchor-points so that you can duplicate each vertical and horizontal line as needed. In the example below I have highlighted all of the lines to be deleted.
Next we will copy and drag the duplicate lines into their correct positions using our orthographic views and the background grid as reference to create our orthographic projections (Fig 12, below). We will also duplicate all of the interior lines so that we can see through our object as if it were transparent as shown in Fig 13 below.
To make our object more appealing visually we will use alternating thick and thin lines and we will also alternate the line colors to differentiate between the exterior and interior of the object. This will make the drawing more readable and understandable to the lay-person.
This simple isometric projection technique can be used on any type of 3-dimensional object, regardless of complexity. All you need to have is each of the object's three dimension's - two side elevation views (left and right, or width and depth) and one overhead plan view, all drawn at the same scale.
Creating an exploded isometric diagram
Once you have a completed isometric drawing of an object it is a relatively simple procedure to take that drawing and create an exploded isometric view. The process only involves taking each individual component or part of the object and separate them (project them) along the diagonal grid plane lines.
Once the individual component parts are spatially separated on the isometric grid you can add connection lines to illustrate how the various parts are interconnected and/or assembled. The ellipses shown in the disc brake illustration (above) are drawn at a 45° ratio - typical isometric ellipses - which is exactly half-way between a perfect circle of 90° and an edge-on view of 0° which would be indicated by a straight line. For information on creating ellipses, see our ellipse tutorial.
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