In the production process, which changes the production object shape, size, location and nature, make it become the process of finished or semi-finished known as process. It's the main part of the production process. The process can be divided into casting, forging, stamping, welding, machining, assembly process, mechanical manufacturing process is the sum of general assembly process refers to the machining process and machine parts of the other process is called assisted process, such as transport, storage, power supply, equipment maintenance etc.. The process is composed of one or more sequential processes, and a process consists of several steps.

The types of production are usually divided into three categories:1. single piece production: individual production of different structures and sizes of products, and rarely repeat.
2. batch production: manufacturing the same product in batches in a year, and the manufacturing process has a certain repeatability.
3. large batch production: a large number of manufacturing products, most workplaces are often repeated processing of a   part of a process.

Design reference: the standard used to determine the location of other points, lines and planes on a part drawing, called the design benchmark.
Process standard: the standard used in the process of machining and assembly, called the process standard. The process datum is divided into assembly datum, measuring datum and positioning datum according to different uses.

(1) assembly datum: the benchmark used to determine the position of a part in a component or product during assembly. It is called assembly datum.
(2) measuring datum: the benchmark used to examine the size and position of machined surface, called the measuring datum.
(3) positioning datum: the datum used in the positioning of workpiece during machining, which is called positioning datum. The surface (or line or point) as the positioning datum can only be chosen as the rough surface in the first process. The positioning surface is called a rough datum, and the machined surface can be used as the positioning datum in each subsequent process. The positioning surface is called the precise datum.