JB/T 4378.1-1999 This standard is a revision of JB 4378-87 "Structural Elements of Metal Cold Stamping Parts". There are slight additions and deletions to the technical content during the revision. This standard is part of the JB/T 4378 "Metal Cold Stamping Parts" series of standards. This series of standards includes the following two parts: JB/T 4378.1-1999 Structural elements of metal cold stamping parts JB/T 4378.2-1999 General technical conditions for metal cold stamping parts This standard specifies metal cold punching, bending, deep drawing and boring Structural elements of parts and common process limit data. This standard applies to cold stamping parts of general structure. This standard does not apply to cold stamping parts and precision blanking parts with special structures. This standard was first published on the year, month and day. JB/T 4378.1-1999 Structural elements of metal cold stamping parts JB/T4378.1-1999 Standard download and decompression password: www.bzxz.net

JB/T4378.1-1999
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This standard is a revision of JB4378-87 "Structural Elements of Metal Cold Stamping Parts". Compared with JB437887, the main technical content of this standard is supplemented and modified as follows: 1) 3.3.1.3 of this standard\Minimum bending radius of commonly used materials\Adopts Table 1 in JB/T5109-1991 "Design Specification for Pressing and Bending Process of Metal Sheets" .
2) The original standard 4.1 "ratio of height to diameter" is canceled in this standard. 3) This standard adds process parameters in 3.5 "Structural Elements of Flared Parts". This standard will replace JB4378--87 from the date of implementation. This standard is proposed and centralized by the National Forging Standardization Technical Committee. The unit responsible for drafting this standard: Xi'an Instrument Factory. The main drafters of this standard: Chen Xingyi, Yang Xiaofeng. 128
1 Scope
Machinery Industry Standard of the People's Republic of China
Structural main factors of metal cold stamping parts for sheet metal stamping partsJB/T4378.11999
Replaces JB 4378--87
This standard specifies the structural elements and common process limit data of metal cold blanking, bending, drawing and boring parts . This standard is applicable to cold stamping parts of general structure. It is not applicable to cold stamping parts and precision blanking parts of special structure. 2 Reference standards
The provisions contained in the following standards are constituted by reference in this standard. The provisions of this standard. When this standard is published, the versions shown are valid. All standards will be revised. Parties using this standard should explore the possibility of using the latest version of JB/T5109--1991 Metal Sheet Materials. Press Bending Process Design Specification 3 Structural Elements of Metal Cold Stamping Parts
3.1 General Principles
3.1.1 The design of stamping parts should be reasonable, and the shape should be as simple, regular and symmetrical as possible to save raw materials and reduce manufacturing processes. , improve the life of the mold and reduce the cost of the workpiece.
3.1.2 Stamping parts with complex shapes can be divided into several simple stamping parts and then made by the connection method. The structural size restrictions given below are based on 3.1.3. The quality and economic benefits of the workpiece are determined. 3.2 Structural elements of the blanking parts
3.2.1 Fillet radius
The shape and inner hole of the blanking parts punched in one go should avoid sharp edges. The clear corners should be properly rounded. ...Generally, the fillet radius R should be greater than or equal to 0.5 times of the plate thickness t, that is, R≥0.5t (see Figure 1) Figure 1
3.2.2 Crush. The hole size
is preferably circular. The minimum size of the punching hole is related to the shape of the hole, the mechanical properties of the material and the thickness of the material. The diameter d or side width α of the free punch punching is as specified in Table 1 || tt||National Machinery Industry Bureau 1999-06-24 approved implementation on 2000-01~01
129
Materials
Steel (α≥690 MPa)
Steel ( oh≥490~690MPa)
steel (oh490) MPa
brass, copper
aluminum, zinc
plastic board, tape board
paperboard| |tt||3.2.3 Protruding concave size
d21. 5tbzxZ.net
da1.3
dal. o
da0.9t
d20 .8t
d0.7t
dz0. 6t
JB/T 4378.1--1999
Table 1
a1.35t
a1.2t
az0.9t
u0.8r
a=0.7t
a0.6t
a0.5t
a1 . 2t
az1.0t
a20.8f
a0. 7t
az20.6t
a0.5t
a0.4t
al. lt
ao. 9z
a0.7t
d0. Gt
4. 5t
0. 1|| tt||0.3t
Narrow cantilevers and convex grooves should be avoided on blanking parts (Figure 2). Generally, the width B of the protruding and concave parts should be greater than or equal to 1.5 times of the plate thickness, that is, B = 1.5t. For hard materials such as high carbon steel and alloy steel, the allowable value should be increased by 30% to 50%. For soft materials such as brass and aluminum, the allowable value should be reduced by 20% to 25%
3.2.4 Hole margins and holes Spacing
The hole margin A should be greater than or equal to 1.5 times the plate thickness t, that is, A≥1.5 (Figure 3), Amin≥0.8mm; the hole spacing B should be greater than or equal to 1.5 times the plate thickness t, that is If B≥1.5t (Figure 3) and Baa≥0.8mm are punched by separate processes or stamped by skip-step die, the value can be appropriately reduced. Figure 2 | | tt | | 3.2.5 End arc size | | tt | | Figure 3 | | tt | 1/2 of B (including positive deviation) (Figure 4), DiR>B/2
Correct
3.3 Structural elements of bending parts
Figure 4||tt| |Wrong
The bending part will change in the bending deformation zone. The smaller the ratio of the bending radius to the plate thickness, the greater the change in the cross-sectional shape. The bending line of the bending part should be perpendicular to the rolling direction. It is best to use the bent and rough bright strip as the outer edge of the bent part to reduce the cracking of the outer layer.
130
JB/T 4378. 1—1999
Springback will occur during bending and forming. The greater the ratio of the bending radius to the plate thickness, the greater the springback. 3.3.1 Bending radius
3.3.1.1 Marking of bending radius: The bending radius r of the bent part is marked on the inner radius 3.3.1.2 It is recommended to select the following bending radius: 0.1, 0.2; 0.3; 0.5; 1.0; 1.5, 2.0;2.5;3.0;4.0,5.0;6.0;8.010.0,12.0,15.0;20.0;25.0:30.035.0;40.0;45.0,50.0;63.0.80.0;100.0mmc3.3.1.3 The bending radius of the bending part should be Choose appropriately, not too large or too small. The minimum bending radius should only be used when structurally necessary.
The minimum bending radius of commonly used materials is selected according to Table 1 in JB/T5109-·1991. 3.3.2 Height of the straight edge of the bent part
In order to ensure the bending quality of the workpiece, when the bend is angular, the straight edge height h of the bent part should be greater than twice the bending radius plus the plate thickness t (Figure 5), that is h>r+2t.
3.3.3 Margin of the hole in the bending part
The edge of the hole on the bending part should be at a certain distance from the bending deformation area to prevent the shape of the hole from being deformed due to bending. Minimum hole edge distance r+2t, (Figure 6)
Figure 5
Figure 6
3.3.4 The bending line of the bending part should not be located at the position of sudden change in size, away from the sudden change The distance 1 should be greater than the bending radius, EI1>r (Figure 7); or cut grooves or punch process holes to separate the deformed area from the non-deformed area (Figure 8). Figure 7 | | tt | | 3.3.5 Art cutting | | tt | | Figure 8 | | tt | 9). Bad hair before bending
Removed by
First
Figure 9
3.4 Structural elements of deep-drawn parts
Cut
Bending line
131
The shape of the deep-drawn parts should be simple and symmetrical. JB/T 4378.1—-1999
The forces on the drawn parts are different at different places, causing the thickness to change after drawing. Generally, the bottom thickness remains unchanged. The fillets between the bottom and the wall become thinner, and the mountains and flanges become thicker.
The side wall of the deep-drawn part should be allowed to have a process slope, but one end must be ensured to be within the tolerance range. For parts that have been drawn multiple times, marks produced during the drawing process are allowed on the inner and outer walls or on the flange surface. In flangeless drawing, the ends are allowed to form lugs. 3.4.1 The bottom fillet radius of the deep-drawn part
The bottom fillet radius r should be selected appropriately, generally 3 to 5 times the plate thickness t. If the structure requires it, the minimum fillet radius rrin should be greater than or equal to the plate thickness t (see Figure 10).
3.4.2 The flange fillet radius of the deep-drawn part
The flange fillet radius r2 should be selected appropriately, generally 5 to 8 times the plate thickness. If the structure requires it, the minimum flange fillet radius rzmin should be greater than or equal to 2 times the plate thickness t (see Figure 10). 3.4.3 Wall fillet radius of rectangular drawn parts When drawing rectangular parts, the four corners will be greatly deformed, and cracks are prone to occur at the bottom of the corners. Therefore, the fillet radius should be selected appropriately and should not be too small. Generally, the wall fillet radius r should be greater than or equal to 6 times the plate thickness. If the structure requires it, the minimum fillet radius r3min should be greater than or equal to 3 times the plate thickness t (see Figure 11).
To facilitate secondary deep drawing forming, the fillet radius r is required to be greater than 15% of the workpiece height h. D | The height of the threaded pre-turning hole is h=(2~~2.5)t. The outer diameter of the threaded pre-turned hole is d, = d + 1.3t (see Figure 12). Figure 12
132
Figure 11
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