Jawaharlal Nehru Technological University Hyderabad B.Tech IV ADDITIVE MANUFACTURING Previous Question Paper (October/November - 2020 - R16)

Conventional machining is a subtractive process where material is removed from a solid block to achieve the desired shape, whereas rapid prototyping is an additive process where material is added layer-by-layer based on a 3D CAD model.

Key differences include:

• Material Usage: Conventional machining results in significant material waste (chips/shavings), while rapid prototyping is highly material-efficient as it uses only what is necessary for the geometry.
• Complexity: Machining is limited by tool access and geometry constraints (e.g., internal cavities are difficult), whereas rapid prototyping can create highly complex, intricate, and hollow internal structures without tooling constraints.
• Tooling: Machining often requires custom jigs, fixtures, and specialized cutting tools; rapid prototyping is tool-less and relies directly on digital data.
• Speed and Cost: Rapid prototyping is faster and cheaper for low-volume production and prototyping, while conventional machining is more economical for high-volume mass production.

Stereo Lithography (SLA) is an additive manufacturing process that uses a vat of liquid photopolymer resin and an ultraviolet (UV) laser to build parts layer by layer.

The process involves the following steps:

1. Preparation: A 3D CAD model is sliced into thin cross-sections.
2. Layer Creation: A UV laser beam is directed by a computer-controlled mirror system to trace the cross-section onto the surface of the liquid resin. The light causes the resin to photopolymerize, turning from liquid to solid.
3. Recoating: Once a layer is cured, the build platform moves down by the thickness of one layer, and a recoating blade spreads a fresh layer of liquid resin over the previously cured surface.
4. Iteration: The process repeats until the entire 3D object is formed.
5. Post-processing: The finished part is removed from the vat, cleaned of excess resin, and typically cured in a UV oven to achieve final material properties.

Applications include:

• Prototyping: Creating high-accuracy visual and functional prototypes with smooth surface finishes.
• Medical: Producing patient-specific anatomical models for surgical planning and dental aligners or surgical guides.
• Investment Casting: Creating master patterns for jewelry and complex metal components.
• Tooling: Producing molds for low-volume injection molding or casting processes.