What are the differences between foreign mechanical drawings and domestic mechanical drawings?
In today's world, ISO international standards stipulate that the first and third angle projections are equally effective. Countries are divided according to national conditions, including Russia, Ukraine, Germany, Romania, Czech Republic, Slovakia and Eastern Europe, all of which use the first angle projection, while the United States, Japan, France, the United Kingdom, Canada, Switzerland, Australia, the Netherlands Countries such as Mexico and the United States mainly use the third angle projection. Before the liberation, China also adopted the third-angle projection. After the founding of New China, the first-angle projection was used. Third-angle projections are often encountered in imported foreign mechanical drawings and scientific books. The ISO International Standard specifies projection marks for the first and third corners (Figures 1 and 2). In the title bar, marked symbols are drawn, and the pattern drawing can be recognized based on these symbols, but some drawings have no projection marks.
2, The third triangle projection
The space can be divided into eight regions by the normal plane V, the horizontal plane H, and the side plane W, which are the first, second, third, fourth, fifth, sixth, seventh, and eighth angles, respectively. 3 is shown.
2.1 The projection of the object in the first angular angle is called the first angular projection, also known as the E method - the European method.
2.2 The projection of the object in the third angular angle is called the third-angle projection, also known as the A method - the American method.
Chinese people usually use the third angle projection method.
The third triangle projection is a method of imagining that an object is placed in a transparent glass box, and each side of the glass box is used as a projection surface, and a figure is obtained by positive projection according to the position of the person-surface object, as shown in FIGS. 4 and 5.
2.3 Position of the six basic views in the third triangle projection
The ISO international standard stipulates that the positions of the six basic views in the third-angle projection are as shown in Fig. 6.
The above view is obtained by projecting an object onto each projection surface of a closed rectangular (transparent) "projection box".
Each view can be understood as the actual image of the object he sees when the observer's line of sight is perpendicular to the corresponding projection surface.
The front view is the observer who imagines that he is in front of the object and moves the position of the eye point by point, and the line of sight is always perpendicular to the imaginary erected projection surface (transparent) to obtain the front projection of the object. Other views can be similarly obtain.
The reader should always view the view as one side of the object itself. From the front view you can see the height and width of the object, as well as the top, bottom, left and right sides of the object. The top view shows the depth and width of the object.
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