by Dennis Collin
AutoCAD is ideal for creation plan, section, and elevation drawings for a range of disciplines. However, on occasion I am asked about how I would go about producing an Isometric drawing. Or is this even possible with AutoCAD LT? The good news is that it is and is easy as creating conventional drawings.
A 2D isometric drawing is a flat representation of a 3D isometric projection. This method of drawing provides a fast way to create an isometric view of a simple design. Distances measured along an isometric axis are correct to scale, but because elements are drawn in 2D, it is not possible to extract other 3D distances and areas, display objects from different viewpoints, or remove hidden lines automatically. If this is required, then the objects will need to be modelled in 3D. This requires full AutoCAD.
Fig 1. Change grid snap settings for aspect and interval
Fig 2. Setting the grid to Isometric Aspect
To produce Isometric drawings, I recommend enabling the Grid snap, set the grid to a suitable interval and toggle the grid behaviour to Isometric mode. Whether using AutoCAD or LT the process and commands are the same.
This can be done either by the Isodraft command, or by my preferred method of the Grid settings, so that the drawing document can be correctly configured for this isometric ‘part’.
Once set notice the grid is at angle looking from the left. This can be toggled to Right or Top by pressing the F5 function key or using the Isometric toggle in the status bar.
Fig 3. Drawing a bracket using Isoplane Left, note the ‘rotated’ cursor and grid
With the grid interval set and snap enabled lines and polylines can be drawn. Taking a bracket kind of shape (250mm square, 30mm thick) as an example the element can be draw in a conventional way with straight lines being constrained with the grid snap and Orthogonal constraint tool. I tend not to use Polar constraint as a rule as Polar is too flexible and can lead to drawing errors. I do use the dynamic input to confirm dimensions and provide impromptu measurements and checks when needed.
When drawing in isometric mode certain object snaps like perpendicular and tangent do not work as expected. As a result, I will draw lines too short or too long and use commands like Trim and Extend to get clean geometry outcomes. (See Fig 3.) Once the ‘left’ side is complete, change the aspect to Isoplane Top (F5) and draw geometry as per Fig 4. Use Trim, Ortho, and other functions as appropriate.
Fig 4. Drawing from Isoplane Top, note the difference in the grid orientation.
If necessary, keep toggling the Isoplane and finish off the drawing as required. Once complete the result will look something like Fig 5.
To return to the normal rectangular grid, return to grid/snap settings and choose Rectanguler Grid. (Fig 1.)
Fig 5. The completed shape!
What about filleted edges and circular holes in whilst drafting in Isometric?
Fillet commands and circles do not understand working in isometric. They will need to be drawn as Ellipses. Also, a tangent Osnap provides ‘interesting’ results. Instead use nearest snap as an alternative. The circular holes need to be drawn as ellipses with an Isocircle option. I will document this workflow in a future blog.
Isometric drafting along with many other more advanced AutoCAD concepts are covered on our Bespoke and follow-on AutoCAD courses. For more details on a range of our courses these please visit https://arkance.world/gb-en/training/
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