Define Additive manufacturing? Explain the basic methodology involved in it. 

Additive manufacturing (AM), commonly known as 3D printing, is a process of creating three-dimensional objects by adding material layer by layer. This is in direct contrast to "subtractive" manufacturing methods, which involve removing material from a solid block to form a final part. AM is a versatile and powerful technology that allows for the creation of highly complex geometries, intricate internal structures, and custom-designed products with minimal waste.

The basic methodology of additive manufacturing generally follows a series of steps:

1. Digital Design: The process begins with a digital blueprint of the object. This is typically created using computer-aided design (CAD) software or by scanning an existing object. The digital file contains a complete geometric description of the part to be printed.

2. File Slicing and Preparation: The digital design is then processed by specialized software, often called "slicer" software. This program converts the 3D model into a series of thin, horizontal layers and generates a set of machine instructions. The instructions guide the 3D printer on where to deposit material for each layer.

3. Material and Machine Setup: The appropriate material for the print, such as a polymer, metal powder, or ceramic, is loaded into the AM machine. The machine is calibrated and prepared to begin the build process.

4. Layer-by-Layer Construction: The heart of the AM process is the layer-by-layer build. The machine precisely deposits, fuses, or solidifies the material according to the instructions from the slicer software. The mechanism for this can vary widely depending on the type of AM technology being used. For example:

   • Material Extrusion (e.g., FDM): A filament is heated and extruded through a nozzle, building the object one layer at a time.

   • Powder Bed Fusion (e.g., SLS, DMLS): A laser or electron beam selectively fuses powdered material within a build chamber. After each layer, a fresh layer of powder is spread, and the process repeats.

   • Vat Photopolymerization (e.g., SLA): A laser or light source cures a liquid photopolymer resin in a vat, hardening it layer by layer.

5. Post-Processing: Once the object is complete, it is removed from the machine. Depending on the technology and material, post-processing may be required. This can include removing support structures, cleaning off excess powder, and performing finishing processes like sanding, heat treatment, or polishing to achieve the desired final properties and surface finish.