1. General
In order to standardize the format of mechanical drawings in the company, make them simple and standardized, and facilitate network sharing, the specifications for mechanical drawings are formulated. This specification applies to the three-dimensional drawings and engineering drawings drawn by Solidworks and Creo software in the mechanical engineering drawing of the company. If any content not specified in this specification is involved in the use process, it shall comply with relevant national standards and regulations.
2. Specifications for the use of drawing software
The content in this part takes Solidworks software as an example, and Creo software is configured and used according to this standard.
2.1. Template selection
When using solidworks to build part models and assembly models, you must use the model templates specified by the company, and the template names are "parts - XX company", "assembly - XX company".
When using solidworks to create engineering drawings, you must use the engineering drawing templates specified by the company, and the template names are "Engineering Drawing A0A1-XX Company", "Engineering Drawing A2A3A4-XX Company".
After the engineering drawing template is selected, select the appropriate drawing format. According to national standards, the company has formulated 5 formats of drawings, including "A0-XX company", "A1-XX company", "A2-XX company", "A3-XX company", "A4 Longitudinal - a certain company". It should be noted that the horizontal format is not allowed for A4 drawings.
2.2. Sketch specification
After creating a new part, if it is an extruded feature, select the top plane for the sketch plane; if it is a revolved feature, select the right or front plane for the sketch plane.
extrude feature
Rotate feature
The drawn sketch must be fully defined (the sketch color is all black), and constraints (perpendicular, parallel, equal, symmetrical, tangent, etc.) should be used as much as possible instead of dimensions to make the sketch fully defined.
2.3. Model specification
After the part and assembly model is established, the "custom attribute card" must be filled in, including: name, pattern code, item number, material, and remarks.
The part and assembly model name naming rules are drawing number + name, and the drawing number and name are consistent with those filled in the attribute card.
2.4. Drawing number specification
The preparation method is: product code + serial number, such as XXX-01-02-00, XXX-01-02-01. Among them, "XXX" indicates the product code, the last digit is "00", which means it is an assembly drawing, and when the last digit is "01", "02", etc., it is expressed as a part drawing. The naming rule of "XXX" is: the English initials of the machine abbreviation + the main parameters of the equipment, for example, MXJ800 means grinding machine, 800 means the maximum processing diameter is 800mm. Generally, the drawing number of a product can only be divided into four layers of part drawings at most, and the detailed division rules are shown in the following figure:
Assembly drawing
XXX-00
The first layer of parts diagram
XXX-01
First floor assembly drawing
XXX-02-00
Parts diagram of the second layer
XXX-02-01
second level assembly
XXX-02-02-00
The third layer of parts diagram
XXX-02-02-01
third layer assembly
XXX-02-02-02-00
The fourth layer of parts diagram
XXX-02-02-02-01
XXX-02-02-02-02
XXX-02-02-02-03
...
The third layer of parts diagram
XXX-02-02-03
...
...
Parts diagram of the second layer
XXX-02-03
...
...
The first layer of parts diagram
XXX-03
first level assembly
XXX-04-00
...
...
2.5. Format specification
1) font
The general requirements are that the drawing should be clear, the font size should be appropriate, and the font (Chinese characters) should be Hanyi Chang Fangsong typeface.
(a) Notes: including part numbers, datum points, geometric tolerances, notes and welding symbols, and the height of the font is recommended to be 3.5mm.
b) Technical requirements: The technical requirements are generally located above the title bar. It is recommended that the word height of "Technical Requirements" in A2, A3, and A4 map frames be 5mm, and the word height of the "Technical Requirements" content part be 3.5mm; The word height of "Requirements" is 7mm, and the word height of "Technical Requirements" is 5mm.
(c) Dimensions: including angle, arc length, chamfer, diameter, hole mark, linearity, dimension chain and radius, and the font height is recommended to be 3.5mm.
(d) Form: The font height is recommended to be 5mm.
(e) View symbol: including auxiliary view, partial view, section view, etc., the font height is recommended to be 5mm.
2) Line type
Line type classification
The thickness of the contour line (thick solid line) and other lines (thin solid line) is clear and appropriate. It is recommended that the width of the thick solid line be 0.35mm, and the width of the thin solid line be 0.18mm. details as follows:
(a) Visible edge: style: solid line; line thickness: 0.35mm
(b) Hidden edge: style: solid line; line thickness: 0.18mm
(c) Sketch curve: style: solid line; line thickness: 0.18mm
(d) Constructive curve: style: center line; line thickness: 0.18mm
(e) Area hatching/filling: style: solid line; line thickness: 0.18mm
(f) Break line: style: double-dot dash line; line thickness: 0.18mm
3) view
Viewing Angle: First Perspective
(a) Section view
When there is only one sectional view in a figure, the sectioned view does not need to be marked with a label, but only needs to indicate the sectioning position and sectioning direction. Unless otherwise specified, the sectioned view does not need to be annotated; when the scale is inconsistent with the sectioned view, the annotation should be annotated and placed directly above the view.
When there are multiple sectional views in one drawing, the sectioned views need to be marked with labels, cutting positions and cutting directions, and annotations should be marked directly above the corresponding sectional views.
(b) Partial view
Basic partial view standard: GB; font: Song; font size: 5.0mm.
Style: with leader.
Labels: Ⅰ, Ⅱ, Ⅲ...marked directly above the partial view: such as , .
(c) to the view
View label: such as direction A, direction B, etc.; marked on the top of the view.
4) other
(a) It is no longer necessary to indicate the quantity of this component "*/unit" in the lower right corner of the "Material" column in the title bar of each component's engineering drawing.
(b) The datum symbol, section view symbol and directional view symbol in each engineering drawing shall be marked with English letters A, B, C, D..., and repeated letters are not allowed.
3. Drawing requirements
3.1. View frame selection
From the perspective of economy, the basic principle of map size selection is: under the premise that the graphics can be expressed clearly, the smaller the size of the map, the better; A4 can be used to express clearly without A3, and A3 can be used to express clearly without A2. If A2 expresses clearly, do not use A1, and if you can use A1 to express clearly, do not use A0. However, the biggest difference between computer drawing and hand-painted drawings is that computer drawing can be partially enlarged infinitely. A common mistake made by newcomers is that the size of the drawing is too small, which leads to unclear markings after printing, which brings troubles to processing personnel.
3.2. Pattern Uniformity
Drawings are works of art, and drawing must consider how to make the view placement reasonable and the drawing surface uniform. The placement of views, dimensions, processing symbols, technical requirements, schedules, etc. are all related to the uniformity of the drawing.
3.3. Drawing scale
The scale of the drawing is selected appropriately, and the proportion recommended by the national standard is preferred, such as 1:1.5×10n, 1:2×10n, 1:2.5×10n, 1:3×10n, 1:4×10n, 1:5×10n, 1 :6×10n, where n=0,1,2…, but in order to make the drawing layout more reasonable, coordinated and beautiful, integer ratios such as 1:7 and 1:8 can be used, but 1:5.5 and 1:6.5 cannot be used Equal decimal ratio.
The ratio of the partial enlargement is the ratio of the drawing size to the actual size. For example, if the scale of the drawing is 1:2, and the partial enlarged drawing enlarges the drawing by 4 times, the scale should be marked as 2:1 instead of 4:1 on the partial enlarged drawing.
3.4. View selection
As long as the shape of the part can be clearly expressed, the fewer views the better. The view that can best express the shape of the component should be selected as the main view, and the top view, side view, direction view, and partial view should be added if necessary, but no redundant views should appear. If a view can clearly express the part without it, and there is no dimension mark on the view, it means that this view can be omitted. Therefore, an important principle of simplifying views is: Views without dimensions can be omitted!
In assembly drawings, welding drawings and other component drawings, it is not necessary to clearly express the structure of all parts, but the assembly relationship of parts, welding positions and outlines of important parts must be clearly expressed.
3.5. Dimensioning
Selection of benchmarks: benchmarks are divided into design benchmarks, manufacturing benchmarks, and measurement benchmarks. Try to unify the three benchmarks to reduce manufacturing errors. During the design process, the convenience of future manufacturing and measurement should be fully considered.
Reference Dimensions: Dimensions do not allow closed and repeated positioning. When some dimensions are really needed (with this dimension, the design intent can be expressed more clearly, and dimension conversion can be avoided), but marking the dimension leads to repeated positioning or closed dimensions, the reference dimension (dimension with brackets) is used to represent it, as shown in the figure below in size (15).
Associative dimensions are expressed in one view as far as possible. Such as the positioning size and shape size of the hole.
Fillet Dimensioning: Bend radii for plates and tubes are dimensioned with inner radii.
Omission of dimensioning: In the dimensioning process, use the manufacturing angle ("Mechanical Engineering Literature" Note: Exactly according to the processing steps) to mark the size (without a certain size, the parts cannot be manufactured ). Pay attention to mark the shape, installation and connection dimensions in the assembly drawing.
Size value: When designing, try to choose the integer size of 5 and 10 for the size of the non-processing surface; choose 34, 58, etc., which are 1~3mm smaller than the integer multiples of 5 and 10. ("Mechanical Engineering Wenhui" Note: On the basis of standard material size specifications, a machining allowance is reserved)
When encountering decimals in dimensions converted from angles, these numbers should be rounded off. For example, the dimension 114.88 can be rounded to 115, and the dimension 33.668° can be rounded to 33.7°. The rounding rules for dimensions with decimals are as follows: Length dimensions can be rounded to one decimal place. Generally, below 0.3 is rounded to 0, 0.3~0.6 is rounded to 0.5, and above 0.6 is rounded to 1. Angle dimensions are generally rounded to one decimal place. Below 0.05 is rounded to 0, above 0.05 is rounded to 0.1.
Dimension lines must not intersect. When dimension lines intersect, it means that the position of the dimension is wrong.
Arrangement of part serial numbers: In the whole figure, the serial numbers are arranged in clockwise or counterclockwise order, and the arrangement in rows is not allowed.
4. Processing symbols
When to use machining symbols? The company custom stipulates that the methods of removing materials such as turning, milling, planing, grinding, sawing, drilling, and boring are processing, and other methods are not processing.
Roughness: If there is no special requirement, the roughness of 12.5 is generally adopted; the surface roughness of any matching surface shall not be lower than 3.2, and the surface roughness of any surface with high requirements (such as vacuum sealing surface) shall not be lower than 1.6. When no processing (such as plate surface, casting surface) is used, the roughness symbol without horizontal lines is used.
5. Tolerance fit
5.1. Dimensional tolerances
Fit selection: interference, transition, clearance fit tolerances are selected according to the tolerances recommended in national standards.
The tolerance labeling of linear dimensions is unified to label the tolerance code and the corresponding limit deviation value at the same time. The value of the limit deviation needs to be enclosed in parentheses, as shown in the figure below:
When marking the fit code of the linear dimension in the assembly drawing, it must be marked in the form of a fraction on the right side of the basic dimension, the numerator is the tolerance code of the hole, and the denominator is the tolerance code of the shaft, as shown in the following figure:
5.2. Geometric tolerances
Focus on explaining the use of position degree. The position degree should be used in large quantities, and the free tolerance cannot meet the position degree requirements of the hole. Generally speaking, the position accuracy is guaranteed by the accuracy of tooling, drilling molds, and processing machine tools. The positioning size between the holes is controlled by the frame size.
Position and frame size: The positioning size is divided into two categories, one is the installation size of a component itself, and the other is the positioning size other than installation. There is a difference between these two types of sizes. The installation size itself cannot have a large deviation, which is represented by the size of the frame, and the size of the frame is inseparable from the position. The labeling method of the size and position of the frame is as follows:
6. Material selection rules
6.1. Material labeling regulations
Each part needs to be marked with the material name, the assembly material column is directly marked with the word "assembly", and the weldment material details column is directly marked with the word "weldment".
6.2. Commonly used material selection
Structural parts: carbon structural steel Q235; stainless steel 304, 304L, 310S, 316L, 3Cr13; aluminum alloy LY12, 7075; cast iron HT250, HT300, etc.;
Drive shaft: 45, 40Cr, 3Cr13, 38CrMoAl, etc.;
Rubber parts: nitrile rubber, fluorine rubber, natural rubber, etc., mostly used as seals and shock absorbers;
Wear-resistant parts: copper, polytetrafluoroethylene, nylon, polyurethane, etc., mostly used as wear-resistant parts or insulation and buffer parts.
7. Welding
7.1. Welding symbols
picture
The meaning of the weld symbol in the figure:
K: weld height;
n: number of weld segments;
L: weld length;
e: weld interval;
N: number of same welds;
The flag is the spot weld symbol; the circle is the circumferential weld number; the two triangles are the symmetrical fillet weld symbol; Z indicates the cross weld. Please refer to the "Machine Design Manual" for details.
7.2. Weld form
Fillet weld: A weld where the weld between two parts is at an angle;
Butt welding: a flush weld between two parts, butt welding is not used for general strength welds;
Overlay welding: The weld seam piled up on the surface of the part is generally used to improve the wear resistance;
Spot welding: a point weld at the weld, used for welding thin plate parts;
Groove Weld: A weld with a groove. There are V-shaped welds with blunt edges, single-sided V-shaped welds with blunt edges, U-shaped welds with blunt edges, single-sided U-shaped welds with blunt edges, horn-shaped welds, and single-sided horn-shaped welds. kind of form. V-shaped and U-shaped welds need to be grooved before welding.
Circumferential welding: Weld a circle around the part or on a certain surface.
Symmetrical weld: A weld that is symmetrical to a component.
Intermittent welding: a welding seam with a blank section after welding.
Z-shaped welding: special for intermittent symmetrical welding, that is, the upper and lower welds are staggered.
Frame welding: three-sided welding in a frame shape.
8. Standard parts selection
8.1. Selection principles of standard parts
The fewer the types of standard parts, the better, try to be unified, and do not increase the standard part specifications at will. Generally, standard parts are selected in the PLM system.
First select the existing standard parts in the PLM system. When the required standard parts cannot be found in the existing standard parts, it is allowed to create a new standard part code and use a new standard part.
8.2. Prioritize the use of standard parts
type
)
Label example
(name column)
Remark
(material column)
Hex socket head cap screw
GB/T70.1
Hexagon socket head screw M12×40
Stainless steel / high strength 12.9
Hexagon socket head screw
GB/T70.3
Hexagon socket head screw M6×16
Stainless steel
Hexagon Socket Head Screws
GB/T70.2
Hexagon socket flat head screw M6×10
Stainless steel
Hexagon Socket Flat Point Set Screws
GB/T77
Hexagon socket set screw with flat end M5×10
Stainless steel
hex head bolt
GB/T5872
Hex head bolt M12×30
Stainless steel / high strength 12.9
Hex nuts
GB/T6170
Hex nut M10
Stainless steel
Flat Washers
GB/T97.2
flat washer 8
Stainless steel
spring washer
GB/T93
spring washer 10
65Mn
Circlip for shaft
GB/T894.1
Shaft circlip 55
65Mn
Circlips for holes
GB/T893.1
Circlip for hole 32
65Mn
9. Component division
Component division is the most basic content of design. If the component division is not good, the whole set of drawings and assembly process will be messy. The basic principles of division are: functional division and physical location division. Functional independence and physical location independence should be divided into components separately. Taking the grinding machine as an example, it is divided into rack column components, motion components, isolation valve components, grinding wheel grinding components, level adjustment components, vacuum system components, waterway components, etc. For the naming rules of the drawing numbers of each component, please refer to the previous figure numbers specification.
10. Common technical requirements writing format
General content of technical requirements:
1) Requirements for materials, blanks, and heat treatment (such as electromagnetic parameters, chemical composition, humidity, hardness, metallographic requirements, etc.).
2) Dimensional tolerances, shapes and surface roughness, etc. that are difficult to express in the view.
3) Uniform requirements for relevant structural elements (such as fillets, chamfers, dimensions, etc.).
4) Requirements for the surface quality of parts and components (such as coating, plating, shot peening, etc.).
5) Special requirements for clearance, interference and individual structural elements.
6) Requirements for calibration, adjustment and sealing.
7) Requirements on the performance and quality of products and components (such as noise, vibration resistance, automation, braking and safety, etc.).
8) Test conditions and methods.
9) Other instructions
The above are the general aspects that should be considered when the technical requirements are given in the drawings of products, parts, and components. For the part drawing or assembly drawing of each drawing code, the above nine aspects are not necessary. Express the specific situation of each object and propose necessary technical requirements
The following points should be kept in mind when writing technical requirements:
1) The writing position of the title and provisions of the "Technical Requirements" should be "as far as possible above or to the left of the title bar". Do not write technical requirements far away from the title bar. Do not write uniform requirements for structural elements (such as "all chamfers C1") in the upper right corner of the drawing.
2) The title of the text description should be "Technical Requirements". If there is only one item, it does not need to be numbered, but the title must not be omitted. "Note" shall not be used instead of "technical requirements"; it is not allowed to write "technical requirements" as "technical conditions". "Technical Requirements" is a part of "Technical Conditions".
3) The terms of the clauses should be concise and standard. In the assembly drawing, when the expression involves parts and components, their serial numbers or codes (design codes) can be used instead.
4) The specific requirements for unspecified tolerances of dimensional tolerances and geometric tolerances should be specified in the technical requirements.
10.1. Surface treatment
Surface treatment: anodized (black, white)
Surface treatment: galvanized
Surface treatment: decorative chrome plating (plating thickness is not marked)
Surface chrome plating: coating thickness 0.××~0.××mm (marking method for hard chrome plating on all surfaces)
Except for the surface of ××, the other surfaces are plated with hard chrome, and the thickness of the coating is 0.××~0.××mm (marking method for a few surfaces without chrome plating)
Hard chrome plating on the surface of ××, the thickness of the coating is 0.××~0.××mm (only a few marking methods for surface chrome plating)
10.2. Painting
All surfaces are painted with paint color number ××
×× surface painted, paint color number ××
Except for the surface of ××, the other surfaces are painted with paint color number ××
10.3. Heat treatment
Heat treatment: quenching and tempering treatment, the hardness after quenching and tempering is HB×××~×××
Heat treatment: surface quenching, surface hardness after quenching HRC ×××~×××, deep ××~××
Heat treatment: surface carburizing (nitrogen), hardness HRC ×××~×××, carburizing (nitrogen) deep ××~××
10.4. Fillet and chamfer
All fillets R×
Unfilled fillet R×
All chamfering××
Unfilled chamfer××
Sharp edge chamfer××
sharp edge not blunt
10.5. Weldments
The surface of all parts must be flat and smooth before welding, without obvious hammer marks
Welds must be penetrated and free from defects such as slag inclusions, cracks, and pores
After welding, each surface should be smooth and the weld seam should be ground
After welding, it must undergo a pressure test under ××MPa pressure for ×min, and there must be no leakage at each weld
The completion of welding must be artificial (natural, vibration) aging treatment (generally used for large weldments)
10.6. Castings
The surface of the casting blank is not machined, and the surface is required to be smooth, and casting defects such as sand holes, shrinkage cavities, and cracks are not allowed.
If the fillet radius of the unfilled casting is ≤ R×, the surface of the casting must be sand-cleaned.
Casting blanks need artificial (natural) aging treatment.
