Recently, a friend approached me regarding CAD. They wanted to upskill for a job during these pandemic times. Being in the same boat, I wanted to help. Consequently, it also made me ponder how I learned CAD around five years ago. However, before we further indulge, let me introduce some CAD history, definition, and application… because, why not?
Overview of CAD
Dr Hanratty of General Motors created the initial framework for CAD in 1961. However, Douglas J. Ross was the first person who coined the word CAD (Computer-Aided Design). Subsequently, AutoCAD from AutoDesk became the first CAD package for individual usage, and thus, revolutionising manufacturing industries. CAD technologies have been evolving and improving ever since.
“Harris, but I just want to learn how to design stuff. Tell me the tips, not the background story!”
If you are impatient like this person, then, it will be a challenging CAD journey for you; more on this later.
Moving on, let me quickly jog your memory. CAD refers to using computing software for designing parts, creating drawings, and testing various manufacturing elements. CAD is a powerful tool which is employed in diverse manufacturing industries these days. Generally, it serves three purposes:
- Creation of 3D-components and engineering diagrams for mass-production later.
- Designing prototypes for comparison and analysis.
- Visualization and modelling parts before manufacturing physical copies.
Furthermore, CAD can be used for dimensioning and tolerancing, producing a bill of materials, Finite Element Analysis (FEA), and even making sustainability reports. Therefore, CAD eliminates many tedious and time-consuming steps, arguably making the overall design process more time-efficient and economical.
Case Study — Designing a Differential Gearbox
I will go through one of my CAD projects for a Formula-style car. Hopefully, it can act as a guideline when you are creating your designs. The package used here is SolidWorks; however, the thought process is mostly valid for other CAD packages such as AutoCAD, CATIA, Onshape, etc.
Embrace Patience; Avoid Getting Overwhelmed
If you are impatient like the person who I mentioned earlier, that is undesired. CAD has a very steep learning curve; it may take years to master. People have been using it for a long time, yet they continuously learn about new functions and tools. Similarly, CAD user interfaces can be quite daunting for beginners. Therefore, patience is required; also, avoid getting overwhelmed when you first open your CAD software as it is a lot to process. It is normal to see new words and be unaware of all functions because you are there to learn. Typical CAD software interfaces look similar to Figure 1.
Embrace Multiple Planes; Avoid Being One-Dimensional… Literally!
CAD sketches are usually in Top, Front, Right/Left Planes, and custom-added planes. In the beginning, I used to start sketches from front planes always. It might not be frowned upon, but it is encouraged to be comfortable starting or manipulating your designs from any axis or planes. It enables more flexibility; many times, you will notice benefits. Your choice of planes should be based on your design process. Do not restrict yourself to just the three given planes. You should know that sometimes particular actions can only be performed via additional custom-planes. Figure 2 shows an example of working on components from both top and front planes.
Embrace Systems Approaches; Avoid Over-simplification
When creating entire systems, differential gearbox, in this case, break the system down into smaller manageable components. Figure 3 shows a breakdown process.
Figure 4 shows that breaking the system into smaller parts aids in efficiently assembling parts.
Also, avoid over-simplifying systems. I would recommend you find a balance; this will depend on your own experience and critical reasoning. To illustrate, Figure 5 shows a simple hex bolt made from the SolidWorks library. You can see that the top, middle, and the shaft sections can be made separately or broken down further. However, it will involve additional steps and merging of smaller part sections; thus, the oversimplification of simple parts can be time-consuming.
Embrace Precision Drawings; Avoid Aesthetic Tendencies
Precision is key. Your part is only as good as how you precisely you can recreate it for mass production. It is critical that you clearly define your sketches so that it can be understood and used at a later time by anyone. Figure 6 shows a sample engineering drawing.
There might be tendencies to make your parts aesthetically pleasing. Good parts are the ones which adhere to engineering drawings, customer requirements, and your PDS (read my other post). Only add rounded corners, smoothening, and flattening of features if it does not affect the mechanism. Figure 7 shows some rendering of the gearbox casing.
Embrace Modifications; Avoid Ignoring Underlying Issues
Lastly, it is smarter to manipulate sketches when creating components through the revolve and sweep features. Beginners tend to design by producing blocks and then extruding in or out without thinking about underlying issues. Furthermore, manipulating transparency of parts also highlights any potential internal design defects and features — see Figure 8.
Not using such functions, ignoring underlying issues, along with a lack of precision and checks, can lead to misfit of parts as highlighted in Figure 9.
However, if your sketches are well defined, you can quickly make modifications to make the parts fit again — as shown in Figure 10.
Ending remarks
There is no hard-and-fast rule when learning CAD. Therefore, take the tips from this article and keep practising with simple and sophisticated systems. Moreover, utilise the built-in libraries and features of your CAD packages for agile designing. In this Industry 4.0 era, CAD technologies are adding novel features continuously. Extensive computer power, storage, smart devices and approaches will further enhance CAD packages and ease of manufacturing in the times to come. Figure 11 shows the completed final design.
That is the end of another article on my 1000 words or less series. I am hoping I can roll out the next article quicker. Let me know your thoughts in the comments. Until then, stay safe; à plus tard!
