Jawaharlal Nehru Technological University Hyderabad B.Tech II AIRCRAFT PRODUCTION TECHNOLOGY Previous Question Paper (July/August - 2021 - R13)

To ensure high-quality die-cast components and extend die life, the following design pitfalls must be avoided:

• Uniform Wall Thickness: Avoiding abrupt changes in wall thickness is critical. Variations cause uneven cooling rates, leading to differential shrinkage, internal stresses, porosity, and warping. Designers should maintain uniform thickness throughout the part.
• Draft Angles: Failure to provide adequate draft angles on vertical surfaces leads to part sticking or surface tearing during ejection. Proper draft ensures smooth release from the die cavity.
• Sharp Corners and Edges: Sharp internal corners act as stress concentrators, leading to premature die failure through cracking. Generous fillets and radii should be used to improve metal flow and structural integrity.
• Deep Pockets and Ribs: Excessively deep pockets or thin, tall ribs are difficult to fill and prone to air entrapment. Ribs should be designed with appropriate thickness and draft to prevent sink marks and ensure complete filling.
• Undercuts: Undercuts require complex, expensive moving die components like slides or cores. They should be avoided or redesigned to allow for a straight-pull ejection whenever possible.

Laser welding is a high-precision joining process, but it faces several limitations and offers specific industrial applications:

Limitations:

• High Initial Cost: The capital investment for laser equipment and sophisticated beam delivery systems is significantly higher than traditional welding methods.
• Joint Fit-up Precision: Laser welding requires extremely tight tolerances for joint fit-up. Because the beam spot size is very small, gaps between parts can lead to lack of fusion or burn-through.
• Cooling Rates: The rapid heating and cooling cycles can result in hard, brittle heat-affected zones (HAZ), which may require post-weld heat treatment to avoid cracking in certain alloys.
• Safety Requirements: High-intensity laser radiation requires stringent safety enclosures and specialized operator training to prevent ocular and skin damage.

Applications:

• Automotive Industry: Used for high-speed, automated welding of car bodies, transmission components, and tailored blanks to reduce weight while maintaining strength.
• Aerospace Industry: Ideal for welding thin-gauge titanium and nickel-based superalloy components where minimal distortion and high weld integrity are mandatory.
• Electronics and Medical Devices: Used for micro-welding of battery tabs, sensors, and delicate medical instruments where heat input must be strictly localized to prevent damage to sensitive components.