Assembly process specifications are usually compiled according to the sequence of operations and steps.
An assembly task completed by one worker or a group of workers without changing equipment or location is called an assembly step. An assembly task completed using the same tools and auxiliary equipment, without changing the working method, and in a fixed continuous position is called a step. An assembly operation may include one or more assembly steps. Both final assembly and component assembly consist of several assembly operations. In terms of product composition, a part is the smallest unit that constitutes a product. Several parts are combined to form a component, making it a part of the product. Regardless of their combination form and method, they are all collectively called components.
Components that directly enter product assembly are called assemblies. Components are assembled from sub-components (parts) at various levels. Sub-components are divided into several levels; the more complex the product, the more levels of sub-components there are. Any level of sub-component is composed of several lower-level sub-components and several parts, and the lowest level of sub-component is also composed of several individual parts. Components that can be assembled independently are called assembly units. In the case of metal furniture, any product can generally be divided into several assembly units. Reference parts and datum components are the foundation of assembly work; both component assembly and final assembly begin from them. Their function is to connect the parts or components that need to be assembled together and to determine the correct relative positions of these parts or components.