Welding is typically used to join two parts together, whether those parts be metal or plastic. There are various styles of welding, but we won’t go into those here.
Casting is the act of pouring a molten metal into a mold, allowing it to cool, and then removing the cooled part from the mold to reveal the castings. After this, it’s quite common to utilize many other manufacturing methods to attain the final part.
Machining is starting out with a block of raw material, and subtractively removing it to eventually carve out the final shape. Much like a rock being chipped away to reveal the final statue. These methods can include manual milling, CNC milling, turning on a lathe for cylindrical objects, and laser/waterjet/EDM cutting, just to name a few.
Additive manufacturing is the process of adding material, rather than taking it away. Whether that be via the fused deposition manufacturing (FDM) seen on many plastic 3d printers, Stereolithography (SLA) using UV light to expose layers to harden a resin, or selective laser sintering (SLS) using a laser to melt particulate together, typically nylons. There are a myriad of technologies out there that fall outside of the ones we just mentioned, but we also won’t go into those here. We’re here to find out about metal 3d printing.