Mechanical drawing is a discipline that uses a pattern to accurately represent the structural shape, size, working principle, and technical requirements of the machine. The drawings are composed of graphics, symbols, words and numbers. They are technical documents that express design intent and manufacturing requirements and exchange experience. They are often called the language of engineering. The origin of the use of the map is very early. For example, in the Song Dynasty, Su Shi and Zhao Gonglian, "The New Instrument Image Method" has a pattern of astronomical timekeeping instruments. In the Ming Dynasty, Song Yingxing also wrote a large number of "Tiangong Kaiwu". Mechanical drawings, but not strict. In 1799, the French scholar Meng Ri published the work of "Drawing Geometry". Since then, the graphics in the mechanical pattern have been drawn strictly in accordance with the projection theory of the descriptive geometry. In order to make people have a consistent understanding of the format, text, graphics, graphic simplification and symbolic meaning involved in the pattern, a unified specification was gradually developed and developed into a mechanical drawing standard. Countries generally have their own national standards, and international standards are set by international standardization organizations. China's national standard for mechanical drawing was established in 1959 and was revised twice in 1974 and 1984. The items specified in the mechanical drawing standard are: drawing format and format, scale, font and drawing lines. The size of the standard sheet of the drawing and the corresponding dimensions of the frame in the drawing are specified in the drawing format and format. The ratio refers to the ratio of the length of the dimension in the pattern to the actual size of the part. Except that it is allowed to draw with a ratio of 1:1, it is only allowed to draw with the reduction ratio and magnification ratio specified in the standard. In China, Chinese characters must be written in long imitation Song, and letters and numbers should be written according to the prescribed structure. The line specification has eight specifications, such as a thick solid line for drawing visible outlines, a dashed line for drawing invisible outlines, a thin dotted line for drawing axes and symmetric centerlines, for drawing dimension lines and profiles. The thin solid line of the line, etc. Mechanical drawings mainly include part drawings and assembly drawings, in addition to layout drawings, schematic drawings, and axis drawings. The part drawing expresses the shape and size of the part and the technical requirements for manufacturing and inspecting the part; the assembly drawing expresses the assembly relationship and working principle between the parts and parts in the machine; the layout shows the position of the mechanical equipment in the factory; The working principle, such as the schematic diagram of the mechanism of the mechanical transmission principle, the schematic diagram of the pipeline expressing the liquid or gas transmission line. Each mechanical component in the schematic is symbolized. Axial drawing is a kind of stereoscopic picture, which is intuitive and is a commonly used auxiliary pattern. A graphic that expresses the shape of a mechanical structure. Commonly used are views, cutaway views, and sectional views. The view is a graphic projected onto the projection surface by the orthographic projection method. The view is divided into a main view, a top view, a left view, and the like, depending on the projection direction and the position of the corresponding projection surface. The view is mainly used to express the outer shape of the mechanism. The invisible outlines in the figure are indicated by dashed lines. When the machine is projected onto the projection surface, there are two relative positions between the observer, the machine and the projection surface. When the machine is located between the projection surface and the observer, it is called the first angle projection method. When the projection surface is between the machine and the observer, it is called the third angle projection method. Both projection methods can express the shape of the machine in the same way. The Chinese national standard stipulates that the first angle projection method is adopted. The cross-sectional view is a hypothetical sectional cutting device, the portion between the observer and the cutting plane is removed, and the remaining portion is projected onto the projection surface to obtain a graphic. The cross-sectional view is mainly used to express the internal structure of the mechanism. The section plan only draws the graph of the cut surface. The cross-sectional view is often used to express the cross-sectional shape of the rod-like structure. For some structures in the drawing that are relatively cumbersome, in order to improve the efficiency of drawing, it is simplified and drawn. The simplified drawing method is called simplified drawing. Mechanical drawing standards have independent standards for the drawing of structures, such as threads, gears, splines, and springs. The drawings are drawn in appropriate proportions according to the structural shape and size of the machine. The dimensions of the parts in the drawing indicate the range to be measured by dimension lines, extension lines and arrows, and the size is indicated by numbers. In mechanical drawings, the unit of the number is specified in millimeters, but no indication is required. For the dimensions such as diameter, radius, taper, slope and arc length, the symbols are added before the numbers to illustrate. When manufacturing the machine, it must be processed according to the size number marked in the drawing. It is not allowed to directly measure the size of the figure from the pattern. The technical conditions required for mechanical manufacturing, such as tolerances and fits, geometrical tolerances, surface roughness, materials and heat treatment requirements, shall be indicated in the drawings by symbols, words and numbers in accordance with the mechanical drawing standards. Before the 20th century, the drawings were drawn by hand using general drawing tools. At the beginning of the 20th century, a mechanical drawing machine appeared, which improved the efficiency of drawing. Computer graphics appeared in the second half of the 20th century. The drawings to be drawn were programmed into a computer, and the computer converted it into graphical information and sent it to the plotter to draw the pattern, or sent it to a computer-controlled automatic machine for processing. The pattern generally needs to be depicted as a transparent basemap, with a transparent baseprint to print out the blueprint or to smoke the purpleprint with ammonia. An electrostatic copying machine appeared in the middle of the 20th century. This type of copying machine can directly copy the original pattern and enlarge or reduce the figure. This new technology eliminates the need for a drawing process. Silicon Calcium Barium Alloy,High Quality Silicon Calcium Barium Alloy,Silicon Calcium Barium Alloy Details, Anyang Penghang Metallurgical Refractory Co., Ltd. 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Mechanical Drawing