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Issue No 60, 22 April 2024
By: Anthony O. Ives
Traditionally before computers engineering components were usually designed with pencil and paper. The disadvantage of designing using pencil and paper if the design changes it requires a lot of work to redo the drawing, even small design changes can require a lot of work. With the development of computers, software programs where created to design in same way as pencil and paper was used. These software programs are usually referred as CAD (Computer Aided Design) packages.
I do not really find computers fun, they can be frustrating and usually do not work exactly the way they are supposed, so I only use them if have to. I usually prefer to use drawing board, pencil and paper if I can [1,2]. I enjoy drawing model aircraft using the old fashioned way. However, designing more complicated things or for a number other reasons for which I will discuss I would use CAD.
When computers work the way they are supposed to they can save time and even be convenient. CAD allows you to design and make all sorts of things using CAM (Computer Aided Machining), CNC machine or in more modern times (at the time of writing!) a 3D printer. CAD therefore is nearly necessary for making helicopter components including RC helicopter parts.
I particularly enjoy using programming to create automated designs. For example if you create a design of a wing or rotor blade using a program then you can resize or reshape your design by changing a number and clicking a button. I explain creating automated designs later in the article.
AutoCAD was the first CAD software package I used. AutoCAD was purely a 2D CAD package when I used it so you could only create 2D plans. AutoCAD can use script files to create automated designs like I described earlier in the article. AutoCAD was also the first CAD package I used to create automated designs. AutoCAD is still used today mainly in the construction industry. AutoCAD is still mainly a 2D CAD package though it may be able to do 3D design models, I have not used AutoCAD since so I am not sure how the latest version works.
CATIA is another CAD package I am familiar with though I have only ever used it to view DMUs (Digital Mock Up) in my professional career but never created anything in CATIA. CATIA is a 3D CAD package which is used extensively in the aircraft and ship building industries. In CATIA you can create a new aircraft in 3D usually referred to as a DMU. Before 3D CAD packages a new aircraft was visualised using a physical mock up or model of the design usually made out of wood, etc. The mock up was to view the design and test for things like fitting, clashes, etc. Now using CATIA this can all be done digitally which of course is all very convenient, cost saving, time saving, etc if everything works as it should and you do not accidentally delete the DMU! CATIA may and probably can also be used to create automatic designs but I am not sure how I never used it enough to find out.
There is a lot of other CAD packages such as Solid Edge which I used to teach engineering students. Solid Edge and other packages will be very similar to CATIA but maybe not with the same functionality but will generally have the same layout, functions, etc. Therefore, usually once you learn to use one CAD it is not too difficult to learn to use another.
Like the name suggests FreeCAD [3] is a free 3D CAD package which uses python [4] as a command script. Python code can be used to create automated designs as described earlier. The picture below shows how python code can be used to create an airfoil.
I plan to learn to use FreeCAD to create automatic designs for helicopters and other helicopter parts, etc. So I plan to create a lot of future articles on FreeCAD.
Another use for 3D CAD is the model can be exported to be used in 3rd party software packages such as those used to anlysis structures, FEA (Finite Element Anlysis) or aerodynamics, CFD (Computional Fluid Dynamics).
CFD stands for Computional Fluid Dynamics and it is a technique used to solve the governing equations of fluid dynamics using numerical methods. In some future articles I plan to explain the theory of CFD in more detail. Like CAD there exist many different software packages to conduct a CFD analysis. I am not going cover all CFD packages in detail but just mention OpenFOAM [5,6].
OpenFOAM like FreeCAD is a free opensource package which uses Paraview [7] for post processing. I plan do a series of future articles looking building models in FreeCAD then exporting the model for analysis in OpenFOAM, etc.
Please leave a comment on my facebook page or via email and let me know if you found this blog article useful and if you would like to see more on this topic. Most of my blog articles are on:
Mathematics
Helicopters
VTOL UAVs (RC Helicopters)
Sailing and Sailboat Design
If there is one or more of these topics that you are specifically interested in please also let me know in your comments this will help me to write blog articles that are more helpful.
References:
[1] http://www.eiteog.com/EiteogBLOG/No6EiteogBlogRange.html
[2] http://www.eiteog.com/EiteogBLOG/No1EiteogBlogLiftCL.html
[3] https://www.freecadweb.org
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