Mechanical drawing is a discipline that uses drawings to accurately represent the structure, size, working principle and technical requirements of machinery. Drawings are composed of graphics, symbols, text, and numbers. They are technical documents that express design intent, manufacturing requirements, and exchange experience. They are often referred to as the language of engineering circles.
In order to enable people to have a consistent understanding of the format, text, graphics, simplification of graphics and the meaning of symbols involved in the drawings, a unified specification was gradually developed and developed into a mechanical drawing standard. Countries generally have their own national standards, and there are international standards established by the International Organization for Standardization.
The items specified in the mechanical drawing standards include: drawing size and format, proportions, fonts and lines, etc. The size of the standard format of the drawing and the corresponding size of the frame in the drawing are specified in the drawing format and format. Proportion refers to the ratio of the length of the dimension in the drawing to the actual size of the machine, except that the ratio of 1:1 is allowed for drawing.
Only the reduced and enlarged scales specified in the standard are allowed for drawing.
Mechanical drawings mainly include parts drawings and assembly drawings, in addition to layout drawings, schematic diagrams and axonometric drawings.
The part drawing expresses the shape and size of the part and the technical requirements for manufacturing and inspection of the part; the assembly drawing expresses the assembly relationship and working principle between the parts and components in the machine; the layout drawing expresses the location of the mechanical equipment in the plant; the schematic drawing expresses the mechanical The working principle, such as the mechanism motion diagram that expresses the principle of mechanical transmission, the pipeline diagram that expresses the liquid or gas transmission line, etc.
The mechanical components in the schematic diagram are represented by symbols.
Axonometric drawing is a kind of three-dimensional drawing, which is intuitive and a commonly used auxiliary drawing.
The figure expressing the shape of the mechanical structure is based on the orthographic projection method (that is, the figure obtained by projecting the machine onto the projection surface). According to the projection direction and the position of the corresponding projection surface, common views are divided into front view, top view, left view and cross-sectional view (formerly called section view).