Thin plate refers to a steel plate whose thickness is much smaller than its length and width.

Its lateral bending resistance is poor, so it is not suitable for the occasion of bearing lateral bending load. Thin plate is metal in terms of its material, but the processing technology of thin plate parts has its particularity because of its special geometric shape and small thickness.

There are three processing technologies related to thin plate components: (1) blanking: including shearing and punching. (2) Forming: including bending, folding, curling and drawing.

(3) Connection: including welding and bonding. The structural design of thin plate members should mainly consider the requirements and characteristics of processing technology.

In addition, pay attention to the batch size of components. Thin-plate components are widely used because thin plates have the following advantages: (1) easy deformation, so that various types of components can be manufactured by simple processing technology.

(2) The thin plate member is light in weight. (3) The amount of processing is small, because the surface quality of the thin plate is high and the dimensional tolerance in the thickness direction is small, so it is not necessary to process the plate surface.

(4) It is easy to cut and weld, and can manufacture large and complex components. (5) The shape is standardized, which is convenient for automatic processing.

2 structural design standards.

2. What knowledge does sheet metal design need?

1, pro/e (sheet metal) board and cad are just drawing tools, and the real technology needs to know the manufacturability of sheet metal.

2. The following is incomplete for reference only, please download it online. Blanking is divided into ordinary blanking and precision blanking. Due to different processing methods, the processing technology of blanking parts is also different.

At present, the structural parts of our communication products are generally only used for ordinary blanking. Next, the blanking process is introduced, which refers to the structural process of ordinary blanking.

2. 1 The shape and size of blanking parts should be as simple and symmetrical as possible to minimize the waste in layout. Fig. 3. 1. 1 layout of blanking parts 2.2 sharp corners should be avoided in the shape and inner hole of blanking parts.

The joint of straight line or curve should be connected by an arc, and the radius of the arc is r ≥ 0.5t. (t is the material wall thickness) Figure 3.2. 1 Minimum radius of blanking part 2.3 The depth and width of the protruding or recessed part of the blanking part should be avoided from the long cantilever and groove, and generally it should not be less than 1.5t(t is the material thickness), and at the same time, long and narrow cuts and narrow cuts should be avoided.

See figure 3.3. 1. Fig. 3.3. 1 avoid the long and narrow cantilever and groove. 2.4 the preferred round hole is drilled. The minimum size of punching hole requires the preferred round hole. The minimum size of punching hole is related to the shape of hole, the mechanical properties of material and the thickness of material.

Fig. 3.4. 1 example of stamping shape material: round hole diameter b rectangular hole short side width b high carbon steel 1.3t 1.0t low carbon steel, brass1.0t 0.7t0.7tAl 0.8t 0.5t* t is the material thickness, and the minimum stamping size is generally not less than 0.3mm. * See Section 7.

Table 1 List of minimum punching sizes 2.5 Hole spacing and hole allowance limit the minimum distance between the punching edge and the shape of the part according to the shape of the part and hole, as shown in Figure 3.5. 1. When the stamping edge is not parallel to the shape edge of the part, the minimum distance should not be less than the material thickness t; Parallel, should not be less than1.5t.

Fig. 3.5. 1 Schematic diagram of hole edge and hole distance of blanking parts 2.6 When punching, the hole wall and straight wall of bending parts and drawing parts should keep a certain distance. When punching, the hole wall of the workpiece should keep a certain distance from the straight wall (Figure 3.6. 1). Fig. 3.6. 1 holes of bending parts and drawing parts. For the countersunk head seat of countersunk head screw, if the plate is too thin to ensure the through hole d2 and countersunk head hole D at the same time, the through hole d2 should be ensured first.

Table 2 Metal plate thickness requirements for screws and bolt through holes t ≥ h ... Table 3 Metal plate thickness requirements for countersunk head seats and through holes of countersunk head screws t ≥ h ..

Table 4 Burr limit value and design mark of blanking parts of countersunk rivets 2.8. 1 The burr limit value of blanking parts is not allowed to exceed a certain height, and the burr height limit value (mm) of stamping parts is shown in the table below. Material wall thickness material tensile strength (n/mm2) >:100 ~ 250 >; 250~400 >400 ~ 630 & gt630 f m g f m g f m g f m g & gt0.7 ~ 1.0 0. 12 0. 17 0.23 0.09 0. 13 0. 17 0.05 0.07 0. 1.03 0.04 0.05 & gt； 1.0 ~ 1.6 0. 17 0.25 0.34 0. 12 0. 18 0.24 0.07 0. 1 1. 15 0.04 0.06 0.08 & gt； 1.6 ~ 2.5 0.25 0.37 0.5 0. 18 0.26 0.35 0. 1 0. 16 0.22 0.06 0.09 0. 12 & gt； 2.5 ~ 4.00.36 0.54 0.720.25 0.37 0.50.20.34 0.09 0.130.18 * f (precision level) is suitable for parts with higher requirements; M grade (mid-range) is suitable for parts with moderate requirements; G grade (coarse grade) is suitable for parts with general requirements.

Table 5 Burr height limit of stamping parts 2.8.2 Marking requirements of burr in design drawings * burr side direction. * Where burr needs to be pressed: coin or coin continues.

Generally, it is not necessary to press all burrs on the fracture of the whole structural member, which will increase the cost. Try to use it in the following situations: exposure of fracture; A sharp edge that the human hand often touches; Holes or slots through which cables need to pass; There is a relatively sliding part.

Figure 3.8.2. 1 Illustration 3 of burr in sheet metal structure design drawing When bending 3. 1 minimum bending radius material of bending part, the outer layer is stretched and the inner layer is compressed in the fillet area. When the thickness of the material is constant, the smaller the internal R is, the more serious the tension and compression of the material will be. When the tensile stress of the fillet exceeds the ultimate strength of the material, cracks and fractures will occur. Therefore, the structural design of bending parts should avoid too small radius of bending fillet.

The minimum bending radius of materials commonly used in the company is shown in the following table. The minimum bending radius of serial number is 1 08, 08F, 1 0, 10F, DX2, SPCC, E 1-T52, 0Cr 18Ni9, 18Ni9 and 659. T2 0.4t2 15, 2 0, Q235, Q235A, 15F 0.5t3 25, 30, Q255 0.6t4 1Cr 13, H62(M, y, Y2, cold rolled) 0.8t5 45.

? T is the thickness of the material, M is the annealed state, Y is the hard state, and Y2 is the hard state of 1/2. Table 6 List of Minimum Bending Radius of Commonly Used Metal Materials in the Company 3.2 Height of straight edge of bending part 3.2. 1 Minimum straight edge height of bending part generally requires that the height of straight edge of bending part should not be too small, and the minimum height should be (Figure 4.2.1): h >; 2t .

Figure 4.2. 1. 1 Minimum height of straight edge of bending part 3.2.2 Special straight edge height If the design requires that the height of straight edge of bending part h≤2t, the height of bending edge should be increased first, and then processed to the required size after bending; Or after machining a shallow groove in the bending deformation zone, bend it (as shown in the following figure). Fig. 4.2.2. 1 Requirements for the height of straight edge in special circumstances 3.2.3 Height of straight edge with bevel on the bending side When there is a bent piece with bevel on the bending side (fig. 4.2.3), the minimum height of this side is: h = (2 ~ 4) t > 3mm Figure 4.2.3. 1 Height of straight edge with oblique angle on bending side 3.3 Hole edge on bending part: punch holes first and then bend, and the position of the hole should be outside the bending deformation zone to avoid hole deformation during bending.

See the table below for the distance from the hole wall to the bending edge. Table 7 hole allowance on bending parts 3.4 process cut for local bending 3.4. 1 the bending line of bending parts should avoid the position where the size changes suddenly. When bending a certain edge locally, the bending line can be moved a certain distance to prevent stress concentration cracking at the sharp corner.

3. Basic knowledge of sheet metal

Sheet metal is a comprehensive cold working process for sheet metal (usually less than 6mm), including shearing, punching, cutting, compounding, splicing and forming (such as automobile body). Its remarkable feature is that the thickness of the same part is consistent.

Sheet metal parts have the characteristics of light weight, high strength, conductivity (can be used for electromagnetic shielding), low cost and good mass production performance, and have been widely used in electronic appliances, communications, automobile industry, medical devices and other fields. For example, computer case, mobile phone, MP3 player and sheet metal parts are all indispensable parts.

Life is inseparable from sheet metal parts. Sheet metal parts are made by filament winding, laser cutting, heavy machining, metal bonding, metal drawing, plasma cutting, precision welding, roll forming, sheet metal bending forming, die forging and water jet cutting.

Extended data

With the more and more extensive application of sheet metal, sheet metal design has become a very important part of product development. Mechanical engineers must master the design skills of sheet metal skillfully, so that the designed sheet metal can not only meet the requirements of product function and appearance, but also make the stamping die simple to manufacture and low in cost.

The base material of SECC is common cold-rolled steel coil. After degreasing, pickling, electroplating and various post-treatment processes, it becomes an electro-galvanized product.

SECC not only has the mechanical properties and approximate machinability of common cold-rolled steel plates, but also has excellent corrosion resistance and decorative appearance. It has great competitiveness and substitution in the markets of electronic products, household appliances and furniture. For example, SECC is widely used in computer chassis.

Modern sheet metal processes include filament winding, laser cutting, rework, metal bonding, metal stretching, plasma cutting, precision welding, roll forming, sheet metal bending forming, water jet cutting and so on.

In three-dimensional software, SolidWorks, UG, Pro/E, SolidEdge, TopSolid, etc. There is a sheet metal part, which mainly obtains the data needed for sheet metal processing (such as unfolded drawing, bending line, etc.). ) By editing 3D graphics and providing data for CNC punching machines, etc.

Baidu encyclopedia-car body panel repair

4. What is a sheet metal structure?

Multi-plate structure is to process and manufacture thin metal plates: thin plates refer to steel plates whose thickness is much smaller than their length and width.

Its lateral bending resistance is poor, so it is not suitable for the occasion of bearing lateral bending load. Thin plate is metal in terms of its material, but the processing technology of thin plate parts has its particularity because of its special geometric shape and small thickness.

There are three processing technologies related to thin plate components: (1) blanking: including shearing and punching. (2) Forming: including bending, folding, curling and drawing.

(3) Connection: including welding and bonding. The structural design of thin plate members should mainly consider the requirements and characteristics of processing technology.

In addition, pay attention to the batch size of components. Thin-plate components are widely used because thin plates have the following advantages: (1) easy deformation, so that various types of components can be manufactured by simple processing technology.

(2) The thin plate member is light in weight. (3) The amount of processing is small, because the surface quality of the thin plate is high and the dimensional tolerance in the thickness direction is small, so it is not necessary to process the plate surface.

(4) It is easy to cut and weld, and can manufacture large and complex components. (5) The shape is standardized, which is convenient for automatic processing.

5. What should I pay attention to in sheet metal design?

Generally, the design is 8 ~10 mm. If the gap is too small, the fan blade will hit the metal sheet when it falls, and then it will be damaged. If the gap between fan blades is too large, the air volume will decrease.

2. The tip of the axial fan should be in the middle of the width of the air guide ring, which will easily lead to the deviation of air volume and noise from the optimal design value. 3. The width of the air guide ring is within 40~50mm, and the diffusion effect is not great if it is too short, and the processing is not good if it is too wide.

4. The center of the axial fan is slightly higher than the height center. Because the lower air volume is slightly higher and the axial fan is slightly higher than the height center, the wind speed on the whole air inlet surface of the condenser can be uniform. 5. The acute angle between the middle partition and the condenser should be as large as possible to avoid poor airflow and low local wind speed caused by frosting.

6. The compressor pipeline should be as small as possible to avoid wasting space. 7. Try to choose an axial fan with good blade shape (large height and diameter, etc.). ).

So as to improve the cooling air volume, reduce the motor speed and reduce vibration and noise. 8. General layout: The distance between the axial flow fan and the condenser should be as far as possible and kept uniform, so as to obtain uniform wind speed and reduce noise. For example, pay attention to the distance between the axial fan and the condenser.

9. The height of the condenser from the chassis should be greater than 5 mm to prevent water from freezing after defrosting. 10. The electrical installation plate should not affect the pipeline space as much as possible.

1 1. The ringing of sheet metal caused by compressor vibration can be solved by sticking anti-vibration glue on the sheet metal. 12. In order to test the feasibility of the outdoor unit structure, destructive experiments and drop experiments must be carried out, so as to find out the design that may have problems as soon as possible and improve it.

Second, the indoor unit design standard (split) 1. The distance between the cross-flow fan and the evaporator surface is preferably above 10mm, so as to avoid the abnormal sound caused by the intake airflow, such as (sudden, sudden ...) 2. Try to choose a multi-fold (more than 2 fold) evaporator, and try to surround the cross-flow fan on the evaporator surface, so as to increase the intake area and reduce the wind speed. 3. The air outlet area of the air outlet frame should be as small as possible (on the premise of ensuring the air volume), so that the air supply speed is easy to ensure, the application applicability is improved, and the cold air and hot air can be sent to every corner of the room as much as possible.

4. The clearance between the air deflector and the face frame should be about 3mm to avoid the air deflector being stuck due to thermal expansion. 5. The diameter of the cross-flow fan should be as large as possible, so that the motor speed is low and the vibration is naturally smaller while ensuring the air volume. At the same time, the clearance between the cross-flow fan and the chassis volute should be greater than 3mm to improve the assembly qualification rate.

6. The ventilation area of the air intake grille should be ensured and as large as possible to reduce the air intake resistance. 7. Try to use advanced cross-flow fans, such as unequal-distance oblique-buckle fans and tower-shaped oblique-buckle fans, so as to obtain continuous compression of air intake and avoid fan blade noise caused by discontinuous air intake of equidistant fans.

8. Long-term operation and water spraying test should be carried out for 15 days to ensure the discharge capacity of condensed water and avoid water dripping to the ground. 9. In order to check the service life of the intake fan panel, it is necessary to open the panel 50~ 100 times (with normal force) without damage.

10. In order to check the structural reliability of indoor units, it is necessary to carry out destructive drop experiments, so as to find and solve problems as soon as possible. 3. Indoor machine (cabinet machine) design 1. The bottommost blade and the topmost blade of the air supply grille should be designed such that the bottommost blade stays horizontal when the blade inclines downward, and the topmost blade stays horizontal when the blade inclines upward, which is beneficial to solving the dew condensation problem.

2. Different air supply volumes (different models) should try to ensure the appropriate air supply distance, which can be solved by reducing or increasing the ventilation area of the air supply outlet. 3. Through the design of the evaporator flow path or air duct, the air temperature of the air supply outlet is as uniform as possible, and the phenomenon that the air outlet is cold and hot is avoided.

4. Because the motor is directly fixed on the backboard, the vibration caused by the vibration of the backboard should be considered, and the connection mode between the motor and the backboard should be adopted as far as possible. 5. The noise of the indoor unit mainly exists in the air inlet, so the air inlet resistance of the air inlet grille should be reduced as much as possible. 6. The installation of evaporator should be inclined as far as possible to improve the heat exchange effect and the uniformity of outlet air temperature.

7. Because the bigger the sheet metal parts of the indoor unit, the better, and it is difficult to guarantee the shape and position tolerance of the whole unit after final assembly, so the zero fit size should be accurate. 8. Transport and drop experiments should be carried out to verify the reliability of structural design.

5. Window machine 1. The louver angle of the outer box should be greater than 45, and the ventilation area should be small enough to improve the outdoor air volume. 2. Because the indoor and outdoor fans use one motor, the indoor and outdoor air volume should be connected in parallel at the same speed, which is convenient for performance design.

3. The distance between the outdoor water thrower (axial fan) and the chassis is about 3~8mm, which is beneficial to draw water and enhance the heat exchange effect of the condenser. 4. Because the air supply area of the condenser is small, the air volume is smaller than that of the condenser, the overall heat exchange capacity is greatly reduced, and heating is easy to frost. Generally speaking, it is not designed as a heating and cooling machine. 6. Dehumidifier 1. The dehumidifier used in low temperature environment should fully consider the reliability of defrosting to balance the dehumidification time of compressor and ventilation defrosting time. During experimental verification, it should be operated for 8-8 years under severe cold conditions such as 10℃.

2. home dehumidifier should be designed with low noise, and the noise value should not be higher than 45db(A). 7. Mobile air conditioner 1. Mobile air conditioner is equivalent to "cold fan", so the distance of air supply is very important, and the air supply speed should be increased as much as possible when the noise allows.

2. Due to the limited windward area and volume of the condenser, users use the exhaust pipe to exhaust hot air to the outside, and the circulating air volume of the condenser will be greatly affected. In order to solve this problem, the design of outdoor centrifugal fan and volute should be strengthened as much as possible. 3. The anti-freezing design of evaporator with dehumidifier should fully consider the operation time of air supply defrosting to avoid evaporator freezing.

6. Basic knowledge of sheet metal

Brief introduction of sheet metal processing technology 1 brief introduction 1. 1 brief introduction According to the basic processing methods of sheet metal parts, such as blanking, bending, drawing, forming and welding.

This specification describes the technological requirements that should be paid attention to in each processing mode. 1.2 Keywords sheet metal, punching, bending, drawing, forming, layout, minimum bending radius, burr, springback, dead edge and welding 2 Punching can be divided into punching, punching, shearing, laser cutting and gas cutting according to different processing methods. Because of the different processing methods, the blanking processing technology is also different.

The blanking methods of sheet metal are mainly punching and laser cutting. 2. 1 Punching is processed by numerical control punching machine. The processing range of plate thickness is cold-rolled plate, hot-rolled plate is less than or equal to 3.0mm, aluminum plate is less than or equal to 4.0mm, and stainless steel is less than or equal to 2.0 mm2. The minimum size of punching hole is related to the shape of hole, the mechanical properties of material and the thickness of material. Fig. 2.2. 1 Example punching shape materials: round hole diameter, short side width of corner cut hole, b high carbon steel 1.3t 1.0t low carbon steel, brass1.0t 0.7tAluminum, 0.8t 0.5t * t are material thicknesses, and the minimum punching size is generally not less than1mm.

* See the list of common company materials corresponding to high carbon steel and low carbon steel in Appendix A of Chapter 7. Table 1 List of Minimum Punching Size 2.3 Hole spacing and hole allowance The minimum distance between the punching edge and the shape of the part is limited according to the shape of the part and the hole, as shown in Figure 2.3. 1.

When the stamping edge is not parallel to the shape edge of the part, the minimum distance should not be less than the material thickness t; Parallel, not less than 1.5t Figure 2.3. 1 Schematic diagram of hole edge and hole distance of blanking parts 2.4 When punching, the hole wall and straight wall of bending parts and drawing parts should keep a certain distance. When punching, the hole wall of the workpiece should keep a certain distance from the straight wall (Figure 2.4. 1). Fig. 2.4. 1 holes for bending and drawing parts.

For the countersunk head seat of countersunk head screw, if the plate is too thin to ensure the through hole d2 and countersunk head hole D at the same time, the through hole d2 should be ensured first. Table 2 Thickness requirements of metal plates for screws and bolt through holes t ≥ h ..

Table 3 Sheet metal thickness requirements of countersunk head screw countersunk head seat and through hole * t ≥ h ... Table 4 Countersunk head rivet countersunk head seat and through hole 2.6 Laser cutting is processed by flying laser machine. The processing range of plate thickness is cold-rolled plate, hot-rolled plate is less than or equal to 20.0mm, and stainless steel is less than10.0 mm.

Its advantages are large processing plate thickness, fast cutting speed of workpiece shape and flexible processing. Its disadvantage is that it cannot be processed and shaped, and the mesh parts should not be processed like this, and the processing cost is high! 3 Bending 3. 1 Minimum bending radius When the material is bent, the outer layer is stretched and the inner layer is compressed in the fillet area. When the thickness of the material is constant, the smaller the internal R is, the more serious the tension and compression of the material will be. When the tensile stress of the fillet exceeds the ultimate strength of the material, cracks and fractures will occur. Therefore, the structural design of bending parts should avoid too small radius of bending fillet.

7. Basic knowledge of sheet metal

Brief introduction of sheet metal processing technology

1 Introduction

1. 1 Introduction

According to the basic processing methods of sheet metal parts, such as blanking, bending, stretching, forming and welding. This specification describes the technological requirements that should be paid attention to in each processing mode.

1.2 Keywords

Sheet metal, blanking, bending, stretching, forming, layout, minimum bending radius, burr, springback, dead edge and welding.

2 blanking

According to the different processing methods, blanking can be divided into ordinary punching, multiple punching, shearing machine cutting, laser cutting and gas cutting. Because of the different processing methods, the blanking processing technology is also different. The blanking methods of sheet metal mainly include punching and laser cutting.

2. 1 Punching is processed by numerical control punching machine. The processing range of plate thickness is cold-rolled plate, hot-rolled plate is less than or equal to 3.0mm, aluminum plate is less than or equal to 4.0mm and stainless steel is less than or equal to 2.0 mm.

2.2 There is a minimum size requirement for punching holes.

The minimum size of punching hole is related to the shape of hole, the mechanical properties of material and the thickness of material.

Figure 2.2. 1 Example of punching shape

Diameter of circular hole of material B and width of short side of rectangular hole B.

High carbon steel1.3t1.0t.

Low carbon steel and brass 1.0T0.7T

Aluminum 0.8t 0.5t

* t is the material thickness, and the minimum punching size is generally not less than1mm.

* See the list of common company materials corresponding to high carbon steel and low carbon steel in Appendix A of Chapter 7.

Table 1 List of Minimum Stamping Dimensions

2.3 Hole spacing and hole edge of several punches

The minimum distance between the punching edge and the shape of the part is defined according to the shape of the part and the hole, as shown in Figure 2.3. 1. When the stamping edge is not parallel to the shape edge of the part, the minimum distance should not be less than the material thickness t; Parallel, should not be less than1.5t.

Fig. 2.3. 1 Schematic diagram of hole edge and hole spacing of blanking parts

2.4 When stamping bending parts and drawing parts, a certain distance should be kept between the hole wall and the straight wall.

When stamping bent or stretched parts, a certain distance should be kept between the hole wall and the straight wall of the workpiece (Figure 2.4. 1).

Figure 2.4. 1 Distance between hole wall of bending parts and deep drawing parts and straight wall of workpiece

2.5 Through holes and countersunk seats for screws and bolts

The structural dimensions of screws, bolt holes and countersunk seats are selected according to the following table. For the countersunk head seat of countersunk head screw, if the plate is too thin to ensure the through hole d2 and countersunk head hole D at the same time, the through hole d2 should be ensured first.

Table 2 Through holes of screws and bolts

* require sheet metal thickness t ≥ h.

Table 3 Countersunk seats and through holes of countersunk screws

* require sheet metal thickness t ≥ h.

Table 4 Countersunk seats and holes of countersunk rivets

2.6 Laser cutting is a flight cutting process with a laser machine. The processing range of plate thickness is less than or equal to 20.0mm for cold-rolled plate and less than 10.0 mm for stainless steel ... Its advantages are large plate thickness, fast cutting speed of workpiece shape and flexible processing. Its disadvantage is that it cannot be processed and shaped, and the mesh parts should not be processed like this, and the processing cost is high!

3 bending

3. 1 Minimum bending radius of bending part

When bending the material, the outer layer is stretched and the inner layer is compressed in the fillet area. When the thickness of the material is constant, the smaller the internal R is, the more serious the tension and compression of the material will be. When the tensile stress of the fillet exceeds the ultimate strength of the material, cracks and fractures will occur. Therefore, the structural design of bending parts should avoid too small radius of bending fillet.