Computer Aided Drafting (CAD) is the process of creating detailed digital models of parts to be manufactured. In this module, you will learn the fundamentals of CAD, understand how it differs from mesh modelling, and create simple designs suitable for CNC machining.

CAD vs. Mesh Modelling

CAD software, such as Fusion 360, focuses on creating precise, parametric models using defined dimensions and constraints. This is different from mesh modelling, which is often used in animation or 3D printing, where models are made up of polygons. While meshes can be used for CNC, they are less suitable for precision and editing as they lack the discrete parts used to enable detailed machining strategies. Meshes are primarily used for carving operations that require high detail but do not have strict precision requirements. Carving is beyond the scope of this training program, but you are encouraged to learn about it and try it on your own.

Basic CAD Concepts

• Sketches: A sketch is a 2D drawing that serves as the foundation for 3D models. Sketches are drawn on planes and define the shapes to be extruded or cut.
• Extrusions: Extrusions convert 2D sketches into 3D objects by extending the sketch along a specified distance. This is one of the most common methods of creating solid features in CAD.
• Other Operations: Additional operations include revolves (creating symmetrical parts by rotating a sketch around an axis), cuts (removing material from a 3D object), and fillets and chamfers (rounding or beveling edges to improve strength and aesthetics).

Output Formats

For CNC machining, the output from CAD must be in a format compatible with CAM software. While Fusion 360 allows direct transition to CAM, exporting a STEP file (.stp or .step) is a common practice when using other CAM systems. STEP files are widely used for sharing models across different CAD and CAM platforms, as they retain precise parametric data.

• Initial Discussion: Discuss your project and learning goals with your trainer to receive feedback on the suitability, design constraints, material selection, and CAD tips if needed.
• Create a 3D Model: Develop a basic 2D sketch and convert it into a 3D model using operations such as extrusions and revolves.
• Understand CAD vs. Mesh: Comprehend the distinctions between CAD and mesh modelling, particularly regarding their limitations for CNC applications.
• Export the Model: Export the completed design as a STEP file if needed. If using Fusion 360, exporting may not be necessary.
• Trainer Review: Share your completed model with the trainer for approval.
• Finalise Design: The approved design will serve as the basis for subsequent modules. Changes after this point may require redoing parts of your work.