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Sheet metal drawing concept
Sheet metal drawing (also known as drawing, drawing, extension) is a typical stamping process of metal processing, through the drawing die to mold flat blanks or hollow parts into a variety of complex shapes and sizes of hollow parts. This process is widely used in stamping production because it can efficiently transform sheet metal into three-dimensional parts with complex shapes. Usually some professional machines and tools are used to complete this work, such as tensile machines, hydraulic clips and disks.
catalogue
1.What is sheet metal stretching
2.Second, deep drawing process characteristics
i. Constant thin drawing features
ii. Thinning and deep drawing features
3.Third, the classification of deep drawing parts
4.Four, sheet metal drawing deformation process
5.Five, drawing mold typical structure
(1) Simple drawing die without holding device;
(2) Drawing die with holding device;
(3) Drawing die drawing with conical holding device;
(4) blanking and drawing composite die;
(5) continuous drawing and die with material.
6.Six, sheet metal drawing design points
★ (1) The shape of the drawing piece
★ (2) Depth of drawing parts
★ (3) The corner of the drawing piece
★ (4) Dimensional accuracy of drawing parts
★ (5) deep drawing die radius value
★ (6) The speed of deep processing
★ (7) punch exhaust in deep drawing process
7.Seven, sheet metal stretching material selection
8.Eight, the advantages of sheet metal drawing
9.Nine, the application of sheet metal drawing
10.Conclusion
First, what is sheet metal drawing?
Sheet metal deep drawing is a metal sheet forming process that uses punches and molds to draw the sheet into the desired shape, often used to make parts that are deeper than the diameter, such as cups, bowls, etc. It uses hydraulic or mechanical presses to produce high precision and smooth surfaces. Widely used in automobile and aircraft production, it can manufacture complex seamless shapes, but the equipment cost is high, and qualified technical personnel and high-quality materials are required. In daily life, many metal products are also made by deep drawing process.
Second, the characteristics of the deep drawing process: the deep drawing process is divided into constant thin drawing and thin drawing. In actual production, constant thin drawing is widely used.
i. Constant thin drawing characteristics: after forming the parts, the thickness of each part is basically the same as the thickness of the billet before drawing.
ii. Thinning and deep drawing characteristics: After forming the part, the wall thickness is significantly thinner than the thickness of the original blank, but the bottom thickness of the deep drawing part is unchanged.
- Classification of drawing parts (cylindrical, curved, box, non-rotating surface)
In stamping production, there are many types of deep drawing. Various drawing parts can be divided into four basic types according to deformation mechanical characteristics, as shown below:
Four, sheet metal drawing deformation process
① Take the drawing process die of cylindrical parts without flanges as an example, as shown below:
1, punch; 2, holder ring; 3, blank; 4, concave die; 5, drawing parts; 6, plane convex part; 7, flange rounded corner part;
- Cylinder wall part; 9, the bottom corner part; 10, the bottom part of the cylinder.
Note: The bottom of the cylinder is divided into non-deformation area, this part of the material is subjected to two-way tensile stress during deep drawing, the thickness of the material will be thin, but the thinning amount is very small, generally only 1% to 3%.
② The force of the material in the process of sheet metal drawing (including: drawing force, compression force, bending force and friction force) is briefly explained, as shown below:
(Attached file name: The force situation of deep-drawing process
③ The force of deep processing
After deep drawing, the thickness and hardness of the cylinder wall of the cylindrical part have certain changes (trace changes for reference), as shown below:
Changes in hardness and wall thickness of the drawing parts along the height direction (trace changes for reference) are shown as follows:
Changes in hardness and wall thickness of drawing parts along height
Five, drawing mold typical structure
The drawing die working on the single acting press can be divided into the drawing die for the first drawing and the drawing die for the subsequent drawing. These two types of molds have a blank holder device and no blank holder device.
(1) Simple drawing die without holding device (Note: remove the positioning ring of the 3 calibration die when working).
1, cone hole pressing block;
2, drawing die;
3, calibration mold positioning ring;
4, drawing punch;
5, positioning plate;
6, die ring; 7.Cushion plate;
(2) Drawing die with holding device
Drawing die with holding device
1 holder screw; 2 drawing punch; 3 holder ring; 4 positioning plate; 5 Drawing die;
(3) Drawing die drawing with conical holding device
1 upper die seat; 2 putt; 3 push plate; 4 conical die; 5 limit column; 6 conical holder ring;
7 drawing punch; 8 punch fixing plate; 9 lower die seat;
(4) blanking and drawing composite die
Blanking and drawing composite die
1 top pole; 2 holder ring; 3 convex and concave die; 4 putt; 5 push plate; 6 discharge plate; 7 blanking die; 8 drawing punch;
The above figure is a typical blanking and drawing composite die, with a formal composite die structure. The upper part of the die is equipped with a convex and concave die 3 (blanking punch and drawing punch), and the lower part of the die is equipped with blanking punch 7 and drawing punch 8.
(5) continuous drawing and die with material
Continuous drawing of the belt material means that the drawing is carried out directly on the belt material, and the parts are blanked from the belt after being drawn. The production efficiency of this deep drawing method is very high, but the mold structure is very complicated, and it is suitable for mass production and small parts. As shown below: continuous drawing limit Drawing coefficient m total
| Material | ultimate strength | elongation | limit total drawing coefficient M total | ||
| No push-off device | with push-off device | ||||
| Material t≤1.2mm | Material thickness t≤1.2~2mm | ||||
| 08F Brass H62、H68；Soft aluminum； | 300~400300~40080~110 | 28~4028~4022~25 | 0.400.350.38 | 0.320.290.30 | 0.160.2~0.240.18 |
(a) Material without cut-out: brass thickness 0.8mm
Attached file name: Non-cutting material brass Thickness 0.8mm
(b) Notched material: 08 steel thickness 1.2mm
(c) continuous drawing die with material
Six, sheet metal drawing design points
★ (1) The shape of the drawing piece
The shape of the drawing part must be kept as simple and symmetrical as possible. Axisymmetric drawing parts deform evenly in the surrounding direction, mold processing is also easy, and its manufacturing performance is the best. Other shapes of deep drawing parts, should try to avoid sharp contour changes.
★ (2) Depth of drawing parts
In general, the depth of drawing is generally not more than 0.2 times the diameter. It’s too deep. It’s easy to break. The maximum drawing depth of commonly used metal materials is shown in the following table.
| Maximum drawing depth of commonly used metal materials | ||
| Schematic | material | maximum depth H |
| Attached file name：Depth of drawn parts | Mild steel | ≤(0.15~0.20）d |
| Aluminum | ≤(0.10~0.15）d | |
| Brass | ≤(0.15~0.22）d | |
★ (3) The corner of the drawing piece
The corner part of each adjacent wall of the drawing part should be transferred with an appropriate size of arc to prevent the corresponding part of the mold from being easy to wear and stress concentration, and the drawing part is easy to be punctured by the right Angle connection. As shown below:
★ Design criteria: the root corner of the drawing R1≥T, the top corner of the drawing R2≥2T, and the corner corner of the drawing R3≥4T. After meeting the above criteria, the larger the radius of the rounded corner, the easier the deep drawing.
★ (4) Dimensional accuracy of drawing parts
The dimensional accuracy of sheet metal parts should not be too high when drawing, and because of the changes in the wall thickness of sheet metal parts, sheet metal parts can only ensure the internal or external size of the feature when drawing, but can not guarantee its internal and external size at the same time.
★ (5) deep drawing die radius value
In the drawing process of sheet metal parts, the value of die radius (Rd) is 60% to 80% of the die radius in the previous drawing process. That is, Rd (n) = (0.6~0.8) Rd (n-1)
★ (6) The speed of deep processing
Sheet metal parts in the drawing processing, the speed should not be too fast, too fast easy to crack the product, the general downward drawing speed is 0.05m/s~0.2m/s.
★ (7) punch exhaust in deep drawing process
Sheet metal parts in the drawing process, the flat punch bottom and blank will form a vacuum, resulting in vacuum pressure, the pressure makes the cylinder is not easy to peel off from the punch, so the punch bottom must drill a hole to eliminate the vacuum pressure.
Seven, sheet metal stretching material selection
Material selection for metal drawing is as follows:
Ⓐ Aluminum alloy: light weight, corrosion resistance, low cost, suitable for automobile, air conditioning, construction and other fields. Good tensile property, high bending strength, corrosion resistance, good electrical conductivity.
Ⓑ Carbon steel: good mechanical properties, low cost, suitable for manufacturing mechanical structure parts, auto parts. Easy to control tensile processing, high tensile strength.
Stainless steel: corrosion resistance, excellent mechanical properties, often used in chemical, medical, kitchen and other fields. Good tensile property and toughness, but high cost.
Ⓓ Other materials: such as titanium alloy, copper alloy, magnesium alloy, etc., each has its own characteristics, need to be selected according to specific needs. When choosing metal drawing materials, it is necessary to consider the cost, performance and use.
Eight, the advantages of sheet metal drawing
High processing precision: Through accurate mold design and advanced drawing technology, to ensure that the product size is accurate, the shape is consistent, to meet the high quality requirements.
Reducing material damage: the material is uniformly deformed during the stretching process, avoiding the problems of heat affected zone, crack and residual stress caused by cutting or welding.
Forming complex structure: with excellent forming ability, it can process complex structural parts with curves, holes, grooves and other characteristics.
Ⅷ High production efficiency: The use of automated production lines, to achieve efficient and continuous processing, improve production efficiency.
Wide range of application: suitable for a variety of materials processing, including stainless steel, carbon steel, aluminum alloy, etc., widely used in automotive, electronics, home appliances, aerospace and other industries.
Nine, the application of sheet metal drawing
Sheet metal drawing processes are widely used in many fields, such as:
1) In the manufacture of kitchen utensils, such as dinner plates and POTS, a deep drawing is used to ensure that the deformation is small and the appearance is beautiful.
2) In the manufacture of fire extinguisher cylinders, the wall thickness is uniform and the safety is improved by multiple deep drawing.
3) In automobile manufacturing, the process is used to produce body parts. In addition, the packaging, aerospace, medical devices, electronic appliances, construction and furniture industries are also widely used to provide high-quality metal parts and components.
conclusion
Sheet metal deep drawing is an efficient and practical metal manufacturing process used to manufacture a variety of high quality and reliable metal parts.
If your project involves sheet metal drawing process, please feel free to contact the Futai manufacturer (Futai@metalsheetprocessing.com), we will be happy to help you. Thank you!