LESSON
3-2 - ISOMETRIC DRAWING
Using Isometric commands is one of the simplest ways to give a 3-D representation while
using only 2-D commands. This has been the usual way
of doing things before CAD allowed true 3-D work to be
done. Many times an isometric drawing is used to compliment or give more information to
a 3 view orthographic drawing. See the sample below.
You can see that it is a very simple drawing.
This basic isometric drawing of the object gives a very
good idea of what it looks like. If this is all that is
needed then isometric works well. Unfortunately, as soon as you change
anything, like the block's height, you'll need to
redraw all four views.
AutoCAD has a command called ISOPLANE which
allows you to easily draw at a 30 degree angle as needed
for an isometric drawing. You can switch between the
three 'isoplanes' (top, right, left) by using this command
or by pressing the F5 key.
Command: ISOPLANE <ENTER>
Current isoplane: Right
Enter isometric plane setting [Left/Top/Right] <Left>: T <ENTER>
Current isoplane: Top
By invoking this command, AutoCAD is now set to draw on
the top isoplane. Your other choices would
be Left or Right. Your first exercise
will be to draw the object shown above using isometric
methods.
Exercise 1 - ISOMETRIC DRAWING
Begin a new drawing using the acad.dwt template
Create a layer called OBJECT and give it a green color.
Make this your current layer.
Type in DDRMODES to
bring up the Drawing Aids dialog box. Make your settings
the same as what you see below (just turn on Isometric
Snap).
Press OK and you'll see
that the grid is set up for isometric drawing
for the left isoplane in 1/2" increments.
Your crosshairs are now angled to show you which
isoplane you are currently on and the Grid is laid out
differently from what you may be used to..
Begin by drawing the left side of the box (shown at the top of the lesson) using the line command.
Ignore the hole at this point. You will want to use
the Direct Distance Entry
System for this exercise and make sure that you have
Ortho (F8) and Osnaps (F3) turned on.
Switch to your right isoplane (F5) and draw the right side.
Switch to your top isoplane (F5) and draw the top view.
Create the angle lines to add the angled surface.
Switch back to the left isoplane and start the ELLISPE command.
At the command prompt, press I for
isocircle. This will allow you to create an ellipse
at the correct angle based on the radius of the circle
in the orthographic drawing. Use the Osnap to pick
the correct center point.
Save your drawing in your CAD folder.
To dimension an isometric drawing, you have to do a few things first. Create a text style called Left, and give it a 30o obliquing angle, then create another called right with a -30o obliquing angle. Then create a new dimension style that has the text aligned with the dimension line. After you have placed a dimension, use the DIMEDIT command to change the obliquing angle of the dimension + or - 30 degrees. You may also need to use the properties to change the text in the dimension to left or right depending upon the orientation of the dimension.
Keep in mind that this is still only 2D. Remember that
in some instances, it may be quicker and easier to use
this method rather than the more complex 3-D methods you'll
be learning in the following lessons.
Extra Practice: Copy this drawing using isometric drawing methods.
Extra Practice: Copy this drawing using isometric drawing methods. If you want to add the hidden lines, jump ahead to Lesson 4-3 to learn about linetypes.
Even More Practice: Try to reproduce these drawings. (Also keep this link in mind when are looking for practice in 3D techniques.)
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