Jawaharlal Nehru Technological University Hyderabad B.Tech III Year UNCONVENTIONAL MACHINING PROCESSES Previous Question Paper (February/March - 2022 - R18)

Modern machining processes are classified based on the primary energy source used for material removal:

1. Mechanical Energy Processes: Includes Ultrasonic Machining (USM), Abrasive Jet Machining (AJM), and Water Jet Machining (WJM). These are used for machining hard, brittle materials like ceramics, glass, and hardened alloys.
2. Electrochemical Energy Processes: Includes Electrochemical Machining (ECM) and Electrochemical Grinding (ECG). These are applied for complex shaped cavities in high-strength alloys and aerospace components.
3. Thermal Energy Processes: Includes Electrical Discharge Machining (EDM), Laser Beam Machining (LBM), Electron Beam Machining (EBM), and Plasma Arc Machining (PAM). These are used for machining extremely hard conductive materials, micro-drilling, and precision cutting.
4. Chemical Energy Processes: Includes Chemical Milling and Photochemical Machining. These are used for producing thin, complex parts like lead frames and printed circuit boards.

Recent developments in Ultrasonic Machining (USM) focus on improving material removal rates and surface finish through hybrid techniques and advanced control systems:

1. Rotary Ultrasonic Machining (RUM): Combines the conventional USM process with diamond core drilling, significantly increasing the material removal rate for brittle materials like carbon fiber reinforced polymers (CFRP).
2. Ultrasonic Assisted Machining (UAM): Incorporates ultrasonic vibrations into traditional cutting tools, which reduces cutting forces, tool wear, and heat generation, leading to improved dimensional accuracy.
3. Micro-USM: Utilizes high-frequency vibrations with micro-tools to create intricate, high-aspect-ratio micro-features in semiconductor materials and glass.
4. Advanced Transducer Design: Development of piezoelectric transducers with higher power density and better thermal stability has allowed for more consistent amplitude control.

The importance of these developments lies in the ability to machine advanced engineering materials (such as composites and superalloys) that are otherwise difficult to process, while simultaneously reducing surface damage and increasing the efficiency of precision manufacturing in the aerospace and medical device industries.