CAD Lab (ME-605) - Important Questions

Explain the steps to create and edit complex free-form surfaces using NURBS in a CAD package. Include trimming, stitching, surface analysis and how to check and ensure curvature continuity, namely $G_0$, $G_1$ and $G_2$ continuity between adjacent surfaces.

Describe and demonstrate the procedure to reverse engineer a physical component into a parametric CAD model using point cloud data and mesh-to-surface techniques. Mention key accuracy considerations, common file formats used (e.g., STL, PLY, IGES) and steps to convert scanned data into feature-based geometry.

Explain the creation of sheet metal components in CAD: creation of base flange, bends, hem, jog and generation of flat pattern. Explain how bend allowance is computed and how K-factor affects the flat pattern. Derive the expression for bend allowance $BA$ for a bend of angle $\theta$ (in radians), inside bend radius $R$, sheet thickness $T$ and K-factor $K$.

Explain mating constraints and interference detection in large assemblies. Describe strategies to manage performance and memory usage in CAD systems when working with large assemblies, including the use of simplified representations, level-of-detail (LOD) configurations and sub-assemblies.

Explain the procedure to generate detailed engineering drawings from a 3D model: creation of orthographic views, section views, dimensioning, application of tolerances and insertion of the Bill of Materials (BOM). Describe how drawing views can be linked so that updates to the 3D model automatically reflect in the drawings.

Explain the concept of parametric design and design intent in CAD. Describe how to implement design intent using equations, global parameters and design tables. Give an example where a single parameter $D$ controls the hole diameter and related sketch dimensions so that changing $D$ updates the part consistently.

Describe the steps to prepare a CAD model for finite element analysis (FEA). Include model simplification/defeaturing, recommended tolerances, meshing considerations (element type and size selection), assignment of material properties, application of boundary conditions and the common export formats for FEA solvers.

Explain the workflow to create CAM toolpaths from a CAD model for milling operations. Discuss selection of cutting tools, machining strategies such as 2D contouring, pocketing and 3D surface machining, and the role of post-processing to generate machine-specific G-code.

What is Geometric Dimensioning and Tolerancing (GD&T)? Explain the meaning and graphical symbol for flatness, perpendicularity, concentricity and positional tolerance. Provide an example of a tolerance frame for a hole position with tolerance value $0.1$ and indicate how Maximum Material Condition (MMC) is represented.

Discuss the concept of feature recognition and knowledge-based machining/automation in CAD/CAM systems. Explain how feature recognition assists in automated NC programming, list typical features recognized, and discuss advantages and limitations of this approach.