Crafting in NieR: Automata is explained on this page.
Players will acquire Materials as they progress through the game that can be combined in order to improve their Weapons. Materials drop from Enemies you defeat and can also be found in various Locations scattered around the world.
Every Weapon can be upgraded up to level 4. The weapons vendors in the Resistance Camp and Pascal's Village can upgrade them to 3. Once achieved, the vendors will refer you to Master Swordsmith Masamune who can bring your weapon to level 4. You'll find him in the Forest Zone. When you reach the side scrolling portion of the castle keep going until you come to the second snake. Past it is a jump. Aim for the lower platform. In the leftmost corner you will hear banging. Move the large crate and head into the room to find him. He will upgrade your weapons to 4 in exchange for money and materials. Eventually he will present you with a special weapon if you upgrade enough weapons.
The following are the various crafting materials you will encounter in the game: