Mechanical manufacturing technology is based on the theoretical knowledge of surface forming, metal cutting and process system, with various processing methods, processing equipment and applications as the main body, and the design of machining process and assembly process as the focus to achieve the production purpose of high-quality and high-efficiency mechanical products. In the mechanical manufacturing technology, the design of the machining process is the focus. Next, we will explain the system to let you know what the content of the machining system is.
The machining process system mainly includes five aspects: production process and technological process, production type, machining allowance, benchmark and general principles for drawing up process route. The following will be described item by item:
1、 Production process and technological process
The production process is the process of making raw materials into products. The technological process is the process of changing the shape, size and performance of raw materials.
2、 Production type
Production types are mainly divided into three categories: single piece production, batch production and mass production.
Single piece production: it refers to the production of a single part with little or no repetition.
Batch production: the production of the same parts in batches.
Mass production: when the manufacturing quantity of a product is large, the production of a certain process of a part is repeated.
3、 Machining allowance
Machining allowance is the excess metal part cut from the blank to meet the qualified standard. Machining allowance is divided into process allowance and total allowance. The machining allowance on the workpiece is mainly to remove the machining error and surface defects left by the previous process, so as to improve the accuracy and surface roughness of the workpiece.
4、 Benchmark
Mechanical parts are composed of pairs of surfaces. As an indispensable part of machining, datum plays an important role in determining the points, lines and surfaces on the parts. In processing, the reference can be divided into design reference and process reference quantity,
1. Design datum: it is mainly used to determine the position of its point, line and surface. For example, the design datum of each outer circle and inner hole of the shaft sleeve part is the axis line of the part.
2. Process datum: the datum used in the processing and assembly of parts. Process datum is divided into assembly datum, measurement datum and positioning datum.
(1) Assembly benchmark: refers to the benchmark of the relative position of components or products used in the assembly process.
(2) Measuring datum: it is mainly used to check the dimension and position accuracy of the machined surface.
(3) Positioning datum: the datum used for workpiece positioning during machining.
5、 General principles for preparing process route
The machining process specification is roughly divided into two steps. The first step is to draw up the process route of parts processing, and then determine the size, equipment, process equipment, cutting specifications, man hour quota, etc. of each process.
The general principles of the proposed process route mainly include the following aspects:
1. Datum first - the datum plane is processed first
During the processing of parts, the surface of positioning reference needs to be processed first, so as to provide precise reference for the processing of subsequent processes as soon as possible.
2. Divide processing stages
For surfaces with high processing quality requirements, the processing stages need to be divided. Generally, they can be divided into three stages: rough processing, semi finishing processing and finishing processing. This is to ensure the processing quality, reasonably use the equipment and facilitate the arrangement of the heat treatment process; And it is convenient to find blank defects.
3. After the hole
The principle of machining the hole on the machining plane first is suitable for machining the box, bracket, connecting rod and other parts. In this way, the holes can be processed by plane positioning, ensuring the positional accuracy of the plane and the holes, and bringing convenience to the processing of the holes on the plane.
4. Finishing of main surface
It shall be carried out at the last stage of the process route to avoid damage to the finished surface due to transfer and installation between processes.
