Baseline introduction editing

concept

Mechanical parts are composed of a number of surfaces, the study of the relative relationship of the surface of the parts, must determine a benchmark, the benchmark is used to determine the position of other points, lines, surfaces on the basis of the point, line, surface. According to the different functions of the benchmark, the benchmark can be divided into two categories: design benchmark and process benchmark.

sort

Design basis: The basis used to determine the position of other points, lines and surfaces on the part drawing is called the design basis.

Process benchmark: The benchmark used in the processing and assembly of parts is called the process benchmark. Process datum is divided into assembly datum, measurement datum and positioning datum according to different uses.

(1) Assembly benchmark: the benchmark used to determine the position of the part in the component or product during assembly, called the assembly benchmark.

(2) Measurement basis: used to test the size and position of the machined surface of the benchmark, called the measurement basis.

(3) Positioning reference: the reference used for workpiece positioning during processing, called positioning reference. As a positioning reference surface (or line, point), in a process can only choose the unprocessed blank surface, this positioning surface is called rough reference. In each subsequent process, the machined surface can be used as a positioning reference, which is a precision reference for the positioning surface.