Improvement of progressive die structure for fins

2022-09-20
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Improvement of progressive die structure for heat exchanger fins

Abstract: in view of the characteristics of serialized and various products, the mold manufacturing process is more reasonable by improving and optimizing the mold structure design

key words: fin layout double entry mold process analysis

1 introduction

fins are one of the important components that affect the heat transfer coefficient in heat exchange equipment. Due to many industries involved, the products are characterized by serialization and diversification. There are more than 10 kinds of fins in various forms and sizes, and the daily demand for each fin is huge. With the continuous expansion of the market, new features have emerged: due to the different heat exchange of the same product, the fin size only changes the height of its spacing, with a total investment of 300million yuan, and other sizes remain basically the same. The distance is determined by the height of the flanging foot of the mountain. For example, according to the conventional mold design, one mold for one part has to be replaced due to the change of flanging foot height, so the variety of fins increases, the demand for molds also increases, and the mold cost is very high. In order to reduce the cost of mold and reduce the variety of mold as much as possible, the structural characteristics of parts are analyzed, and the original mold structure is improved, so that a pair of mold can punch multiple fins

the part shown in Figure 1 belongs to medium-sized fin. The material of the part is Q235-A and the material thickness is o.3mm. It is named X-shaped fin according to its shape. Taking this fin as an example, this paper discusses the improvement of die structure to achieve the purpose of punching fins with multiple spacing, so as to avoid affecting the measurement results, reduce the number of dies and reduce the cost as much as possible

2 process analysis

the spacing of fins is mainly determined by the height of flanging feet. Most of the parts in several series used now are only changed in spacing, and other sizes are basically the same. At present, there are three kinds of spacing for X-shaped fins, such as 2.5mm, 3mm and 4mm. With the continuous expansion of the market, new varieties are being added. According to the conventional mold design, punching fins with three spacing requires manufacturing three molds, and at least one additional mold needs to be prepared for each one for maintenance and turnover, so the number of molds is large and the cost is high. According to the shape of fins, analyze the structural characteristics of the die, and consider how to improve the structure so that a pair of dies can punch fins with several spacing

3 key points of mold structure design and improvement

3.1 layout

layout design (including cutting) has 4 steps. That is, cutting triangular notch, punching, flanging and turning distance feet, cutting, 53mm is a step; Referring to the design of layout and overlap in Die Design Manual (Part IV) of the die manual, the edge measurement size on both sides is determined to be 2.5mm, and the width of the steel strip is 113mm; The punching material is Q235-A, and the material thickness is ≤ 0.5mm. It can be seen from the layout diagram shown in Figure 2 that the layout form of the mold is straight row, and there is no overlap between parts, which is characterized by material saving. Moreover, the waste and parts have been separated in the punching process, which is convenient for sorting and collecting waste and parts. In addition, because the outside of the female die is a cutting edge, the parts are taken out from one side of the machine tool. Even if they are collected, we can also install a threading machine outside the stamping equipment in combination with the product characteristics of our factory, so as to realize the automation of punching and threading

3.2 mold structure

mold structure is shown in Figure 3

1 backing plate 2 unloading screw 3 fixing plate 4 side edge 5 unloading plate 6 trapezoidal punch 7 circular punch 8 rhombic punch 9 flanging punch 10 flanging top core 11 flanging punch 12 small guide pillar 13 concave die 14 lower backing plate 15 cutter 16 top core 17 lower die base 18 baffle 19 trapezoidal top core 20 top spring

(1) die working process

in the first step, the strip is fed by the automatic feeding device, enters through the baffle plate 18, and the triangular notch is punched out by the side edge 4. It can be seen from the fin layout that the triangular notch of this step punch is composed of small triangles on both sides of the fin

the second step is to punch the round punch 7 and diamond punch 8, and the trapezoidal punch 6 cuts out the three sides of the six spacing feet

the third step is to turn the round hole out of the flanging punch 9 and the spacing foot out of the punch 11

finally, the basically formed parts are sent out of the die, and the parts are cut by the outer edge of the die and the cutter, and the parts fall into the container

when the unloading plate 5 works, it presses the strip. When the upper die goes up, the flanging punch smoothly exits the flanging hole. The trapezoidal top core 19, flanging top core 10 and top core 16 push the strip out of the concave die by the push of the spring and feed it smoothly. Four small guide legs are installed on the fixed plate 3 and pass through the unloading plate 5. During the work, the small guide pillars enter the guide sleeve hole of the concave template. The discharge pole 5 always slides on the small guide post, which has a good positioning effect and protects the punch 6 and 11

the die is installed on the high-speed punch with automatic feeding device for stamping, which requires high precision and good rigidity of the die. Therefore, the four guide pillar ball die base is adopted. Working parts are made of Crl2MoV steel, with heat treatment hardness of HBC, other supporting parts are made of 45 steel, and parts with large stress such as discharge plate, baffle and top core are subject to quenching and tempering treatment, with hardness of 45 ~ 48hrc

(2) improvement points

the difference of fin spacing is reflected in the flanging height of the spacing foot. First of all, consider the cutting edge of the spacing foot. Trapezoidal punch 6 cuts three edges of the spacing foot. If the spacing is large, the cut edge will be long. Then turn out the spacing foot by the punch 11. At present, there are three spacing sizes of X-shaped fins, which are 2.5mm, 3mm and 4mm respectively. The difference is o.5mm and 1mm, and the size difference is not big, so can we only cut a maximum size, and the height is guaranteed by turning the foot, as shown in Figure 4

after discussion and analysis, two solutions are proposed. One is that there is little difference in the length and size of the trimming. When trimming, the Eucalyptus should be trimmed with a spacing of 4mm. Then consider the position of the turnover foot on the die according to the required spacing height. The second is to determine the length of the cutting edge by controlling the depth of the trapezoidal punch entering the concave chopsticks. This method has high requirements for mold maintenance and debugging. After comparison, it is better to choose the first scheme when the length and size of the trimming are not much different

the problem of sharing trapezoidal punch is solved, and the next step is to solve the problem of female die

from the experience summed up in practice, there are many factors that affect the height of flanging foot, such as the length of trapezoidal convex transverse edge, the hardness of steel strip, the size of the gap between flanging punch and female die, the determination of the accuracy of flanging position on female die, etc. Among them, the accuracy of determining the flanging position of the die is the key and has the greatest impact. This factor can be solved by improving the structure in order to occupy an active position in the market

in practice, we have mastered the change law of flanging height, so we have determined the location and size of flanging. There are four turnover holes on the die, and the space between the turnover holes is large. The turnover hole can be designed as an insert, which adopts the cooperation of h7/n6. The spacing can be changed by replacing the female die insert and the corresponding turning over punch, and the fins with different spacing can share a female die. The adoption of the insert form is also convenient for the correction of the turning over height dimension

4 conclusion

the mold structure design is reasonable, and the mold investment cost is reduced. After verification, the effect is good, which can meet the needs of mass production, and has achieved significant economic benefits. It also accumulates design experience for other similar situations

references

1 Xu fayue's practical die design and manufacturing manual. Machine press, 2002

2 die manual four die design manual. Machine press 1988 (end)

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