I. Machining Process
Machining processes involve altering the shape, size, relative position, and properties of the object being produced, based on existing procedures, to transform it into a finished or semi-finished product. Each step and process is a detailed description. For example, as mentioned above, rough machining might include blank manufacturing and grinding, while finish machining might involve turning, fitting, milling, etc. Each step requires detailed data, such as the required surface roughness and tolerance.
Based on factors such as product quantity, equipment conditions, and worker skills, technicians determine the appropriate technological process and document the details in a process specification document. This process specification is quite specific and may vary from factory to factory because the actual circumstances differ.
In general, the process flow is the outline, the processing technology is the detailed parameters of each step, and the process specification is a specific processing technology written by a factory based on its actual situation.
II. Machining Process Specifications
Machining process specifications generally include the following: the process route for workpiece machining, the specific content of each process and the equipment and tooling used, the workpiece inspection process and inspection methods, cutting parameters, time quotas, etc.
1. Production process
The production process refers to the entire process of transforming raw materials (semi-finished products) into finished products. The production process of mechanical products generally includes:
① Production and technology preparation, such as process design and the design and manufacture of special process equipment, production planning, and preparation of production materials; ② Blank manufacturing, such as casting, forging, and stamping; ③ Parts processing, such as cutting, heat treatment, and surface treatment; ④ Product assembly, such as final assembly, sub-assembly, debugging, inspection, and painting; ⑤ Production services, such as the supply, transportation, and storage of raw materials, purchased parts, and tools.
2. Technological Process
A technological process refers to the process of changing the shape, size, relative position, and properties of a production object during production, so as to make it a finished or semi-finished product. Examples include the manufacturing of blanks, machining, heat treatment, and assembly.
In the manufacturing process, the process of directly changing the shape, size, and surface quality of a production object through machining to make it a qualified part is called a machining process. Similarly, the process of assembling machined parts into a machine to achieve the required assembly accuracy and obtain predetermined technical performance is called an assembly process.
Machining processes and assembly processes are two main areas of study in mechanical manufacturing technology.
The machining process consists of one or more sequential steps, which can be further divided into several installations, workstations, steps, and tool passes. The blank is transformed into a finished product through these sequential steps.
1. Process
A process refers to the part of a technological procedure that is continuously completed by one or a group of workers at one work site on one or several workpieces simultaneously. A process is not only the basic unit that makes up a technological process, but also the basis for setting time quotas, allocating workers, arranging work, and conducting quality inspections.
A simplified process that only lists the names of the main steps is usually called a process route.
2. Installation and workstations
Before machining, the process of locating a workpiece in a correct position on a machine tool or fixture, and then clamping it, is called clamping. The part of the process completed after a workpiece (or assembly unit) is clamped once is called installation. One or more installations can occur in a single operation. The number of clamping operations should be minimized during workpiece machining, as each additional clamping operation introduces an additional clamping error and increases auxiliary time. Therefore, various rotary tables, rotary fixtures, or moving fixtures are commonly used in production to allow the workpiece to be processed in different positions after a single clamping. To complete a specific process, each position occupied by the workpiece (or assembly unit) and the movable part of the fixture or equipment relative to the fixed part of the tool or equipment after a single clamping is called a workstation.
3. Process steps and tool movement
1) Work steps
A machining step refers to the continuous part of a process performed while keeping the machined surface (or connecting surface during assembly) and the cutting (or assembly) tool unchanged. A process can include several machining steps or only one machining step.
2) Cutting
If the metal layer to be removed from the machined surface is very thick within a single machining step, requiring multiple cuts, then each cut is considered a tool pass. A machining step can include one tool pass or several tool passes.
