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Principles for selecting views: (1) While ensuring the object is clearly represented, the number of views (including front views, sectional views, etc.) should be kept to a minimum. (2) Try to avoid using dashed lines to represent the contours and edges of objects. (3) Avoid unnecessary repetition. Drawing principles: For the purposes of processing, assembly, etc., each piece of equipment, component, or part should have its own separate drawing. 1. The principles for not requiring separate pattern drawing are as follows. (1) **Standard, professional standard, and other standard components and purchased parts. (2) For riveted and welded parts with a simple structure, whose dimensions, shapes, and other details are already clearly indicated on the component drawing, and that do not require mechanical processing (with the exception of operations such as weld groove preparation and minor drilling), (3) for several castings that need to have their molds marked together during the manufacturing process, drawings should be prepared according to the component drawing; there is no need to create separate part drawings. At this point, all the information required to manufacture the part must be indicated on it. (4) For connecting parts such as bolts, nuts, washers, and flanges whose dimensions meet the standards, even if their materials differ from those specified in the standards, separate part drawings are not prepared. However, indicate the specifications and materials in the details column, and write “Dimensions shall comply with××× standards” in the remarks column. At this time, the \"Drawing Number or Standard Number\" field in the details column should not indicate a standard number. (5) Two parts that are symmetrical to each other but in opposite directions should generally be drawn as separate drawings. But for two simple symmetrical parts, it is possible to draw only one of them without causing construction errors. However, each bid item shall be assigned a different part number, which shall be indicated in the drawings. For example, “This pattern represents part number ×, and part number × is symmetric to part number × on the left (or right) (or above/below).” (6) Parts that have the same shape, simple structure, and can be clearly represented by the same drawing, with generally no more than 10 different variable parameters, may be depicted using a tabular format; however, the following rules must be followed: ① The common constant parameters and textual descriptions must be indicated in the drawing, while the variable parameters should be denoted by letter codes ； ②The table must include the part number, as well as the quantity and quality of each variable parameter. 2. The principles for drawing component drawings separately are as follows. (1) Parts that must be machined after being assembled due to processing requirements or design needs should have a part drawing. Such as equipment flanges with short sections, large gears made up of two halves, worm gears composed of parts made from two different materials, etc. For simple components without detailed part drawings, it should be indicated in the part drawing that machining can only be carried out after assembly. Such as phrases like “× surface must be processed after welding with part number ×”. (2) Detachable or non-detachable components that have an independent structure and for which a component drawing is necessary to clearly illustrate their assembly requirements, mechanical properties, and uses should be provided with such a drawing. Such as stirring drive devices, split bearings, couplings, etc. (3) Detailed drawings of the components should be provided for complex equipment housings. (4) Part drawings should be prepared for cast and forged parts. 3. Principles for drawing enlarged views: Enlarged views are required for the butt welds between the cylinder and the head, the welds between the reinforcement rings and the cylinder or head, the reinforcement welds on thick-walled pipes, the welds between the cylinder and the tube sheet, the welds between the cylinder and the skirt, and the connection welds.