(SEM VI) THEORY EXAMINATION 2024-25 CAD/CAM

BME602 – CAD/CAM

Section-Wise Solved Answers (2024–25)

SECTION A

Attempt all questions in brief (2 × 7 = 14 marks)

(a) What do you understand by CAD/CAM?

CAD (Computer Aided Design) is the use of computer systems to create, modify, analyze, and optimize product designs. It helps engineers prepare accurate drawings, models, and simulations.
CAM (Computer Aided Manufacturing) uses computer software to control machine tools and manufacturing processes. CAD/CAM integration improves productivity, accuracy, and reduces manufacturing time and errors.

(b) What is clipping?

Clipping is the process of removing parts of graphical objects that lie outside a specified viewing area. It ensures that only the visible portion of objects inside the window or viewport is displayed on the screen.

(c) What are the different types of geometric modeling?

Geometric modeling techniques include wireframe modeling, surface modeling, and solid modeling. Wireframe shows only edges, surface modeling defines surfaces without volume, while solid modeling represents complete 3D objects with volume and mass properties.

(d) What are rational curves? How do they differ from non-rational curves?

Rational curves use weighted control points and are capable of representing exact conic sections such as circles and ellipses. Non-rational curves do not use weights and cannot represent conic sections exactly. Rational curves offer greater flexibility and accuracy.

(e) Differentiate between CNC and DNC machines.

CNC machines operate independently with programs stored locally, while DNC systems use a central computer to control multiple CNC machines. DNC improves data management and is suitable for large manufacturing setups.

(f) What is the function of various G codes and M codes?

G codes control machine tool movements such as linear and circular interpolation. M codes control auxiliary functions like spindle ON/OFF, coolant control, and tool change operations.

(g) Explain classification and coding.

Classification and coding is a system of grouping parts based on design and manufacturing similarities. Each part is assigned a code that represents its shape, size, material, and processing method, helping in standardization and automation.

 SECTION B

Attempt any three (7 × 3 = 21 marks)

(a) Bresenham’s line algorithm for points (20,10) and (30,18)

Given:
Δx = 10, Δy = 8, slope = 0.8

Using Bresenham’s algorithm, pixel positions are generated incrementally by deciding whether to move horizontally or diagonally based on decision parameter. The plotted points closely approximate the straight line with minimum computational effort, making the algorithm efficient for raster displays.

(b) Constructive Solid Geometry (CSG)

CSG is a solid modeling technique that creates complex objects by combining simple geometric primitives like cubes, cylinders, and spheres using Boolean operations such as union, intersection, and difference. Primitives define basic shapes, while Boolean operations combine them to form complex solids.

(c) Quadric, superquadric surfaces and blobby objects

Quadric surfaces include spheres, cylinders, cones, and ellipsoids defined by second-degree equations. Superquadrics are generalized forms that allow shape variation using exponent parameters.
Blobby objects represent smooth organic shapes formed by combining field functions, commonly used in animation and biomedical modeling.

(d) CNC program for taper turning (outline explanation)

The taper turning operation is programmed using linear interpolation commands. The program includes tool positioning, spindle control, feed rate selection, and linear movement from larger diameter to smaller diameter along the specified length.

(e) Group Technology (GT) and adaptive control

Group Technology is a manufacturing philosophy that groups similar parts to improve efficiency. GT reduces setup time, tooling cost, and improves productivity.
Adaptive control automatically adjusts machining parameters based on cutting conditions, improving tool life, surface finish, and machining accuracy.

SECTION C

Attempt any one (7 marks)

(a) Transformation of triangle coordinates

Initial vertices:
A(0,0), B(5,5), C(8,8)

Step-1: Translation by 3 units in y-direction
A′(0,3), B′(5,8), C′(8,11)

Step-2: Rotation by 45° anticlockwise
Using rotation matrix, new coordinates are obtained.

Step-3: Scaling by 3 units in x-direction
Final coordinates are obtained by multiplying x-coordinates by 3.

(b) Bezier curve through control points

Given control points (2,0), (5,4), (6,3), (4,3).
Bezier curve is generated using Bernstein polynomial equations. The curve smoothly follows the shape defined by control points and lies within their convex hull.