JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD B.Tech IV UNCONVENTIONAL MACHINING PROCESS Previous Question Paper (March - 2021 - R16)

Conventional machining relies on mechanical force and a tool harder than the workpiece to induce plastic deformation and shear. As material hardness increases, the required cutting force rises, leading to rapid tool wear, high heat generation, and potential surface damage. In contrast, non-conventional machining processes utilize alternative energy sources such as electrical, chemical, thermal, or electrochemical energy to remove material.

These processes do not depend on the relative hardness of the tool and workpiece. For instance, Electrical Discharge Machining (EDM) removes material through thermal erosion via sparks, while Electrochemical Machining (ECM) uses anodic dissolution. Because these methods involve minimal or no direct mechanical contact and do not rely on shear strength, they can machine materials of any hardness, including superalloys, ceramics, and hardened steels, without the limitations of tool-workpiece hardness ratios.

Selecting an appropriate non-conventional machining process requires evaluating several critical parameters to ensure technical feasibility and economic viability:

• Workpiece Material Properties: The electrical conductivity, thermal conductivity, chemical reactivity, and hardness of the material determine the suitability of processes like ECM (conductive materials only) versus laser or ultrasonic machining.
• Geometry and Complexity: The shape, depth of cut, and aspect ratio of the features dictate the choice. For example, EDM is excellent for deep, complex cavities, while Water Jet Machining is better for intricate 2D profiles in sheet materials.
• Surface Integrity and Accuracy: Requirements for surface finish, dimensional tolerance, and the presence of a Heat Affected Zone (HAZ) are vital. Thermal processes like EDM may create a recast layer, whereas chemical or electrochemical processes provide stress-free surfaces.
• Material Removal Rate (MRR): The required production volume influences the choice; processes with high MRR are preferred for mass production, though they may compromise finish.
• Economic Factors: Total cost, including initial capital investment, tooling costs, power consumption, and maintenance, must be balanced against the production rate and part quality.
• Environmental and Safety Considerations: Processes involving hazardous chemicals, high-pressure fluids, or ionizing radiation require specific safety protocols and waste management systems.