What is the main difference between additive and subtractive manufacturing processes?

The main difference between additive and subtractive manufacturing processes is that additive manufacturing builds products layer by layer. This process involves adding material to create an object, typically using techniques such as 3D printing, where layers of material are deposited in succession until the final product is formed. This method allows for greater design flexibility and the creation of complex geometries that may be difficult or impossible to achieve with traditional methods.

In contrast, subtractive manufacturing involves removing material from a solid block to achieve the desired shape and size. This process can include techniques like milling, turning, or drilling, where material is cut away from a larger piece to create the final product. The unique advantage of additive manufacturing is its ability to construct parts with intricate details without the need for extensive tooling or molds.

Options that state that additive relies on heat, uses molds, or removes material do not accurately capture the fundamental aspects of additive manufacturing. Instead, they confuse it with features of subtractive manufacturing or other manufacturing processes. Thus, the ability to build layer by layer distinctly characterizes additive manufacturing, making it the correct focus for the question.