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Home > Industry Information > Improvement of fin-stage progressive die structure of heat exchanger

Improvement of fin-stage progressive die structure of heat exchanger

2018-08-06

[Abstract] For the serialization and various types of product features, the mold manufacturing process is more reasonable by improving and optimizing the mold structure design.
Key words fin-type double-injection process analysis

1 Introduction

The fin is one of the important components affecting the heat transfer coefficient in the heat exchange equipment. Due to the many industries involved, the products are characterized by serialization and diversification. There are more than 10 types of fins in various forms and sizes, and the daily demand for each type of fin is huge. With the continuous expansion of the market, new features have emerged: the same product has different heights due to the difference in heat exchange, and the other dimensions are basically unchanged. The height of the foot is determined by the height of the foot. For example, according to the conventional mold design, a part of a pair of molds, because of the change in the height of the flanged legs, the mold has to be replaced, then the number of fins increases, the demand for the mold increases, and the cost of the mold is high. In order to reduce the cost of the mold, the mold variety is reduced as much as possible, the structural characteristics of the parts are analyzed, and the original mold structure is improved, so that a pair of molds can be punched into a variety of fins.

The parts shown in Figure 1 are medium-sized fins, the part material is Q235-A, and the material thickness is O.3mm. It is named x-shaped fin according to its shape. Taking the fin as an example, the structure of the mold is improved, and the purpose of punching a plurality of fins is achieved, and the number of molds is reduced as much as possible, and the cost is reduced.
2 Process analysis

The spacing of the fins is mainly determined by the height of the flanging feet. Most of the series of parts used now only change in the spacing, and the other dimensions are basically the same. At present, there are three kinds of pitches of 2.5 mm, 3 mm, and 4 mm for the X-shaped fins. As the market continues to expand, new varieties are being added. According to the conventional mold design, it is necessary to manufacture three sets of molds for punching three types of fins, and at least one pair of molds is required to be used for maintenance and turnover, so that the number of molds is large and the cost is high. According to the shape of the fin, analyze the structural characteristics of the touch tool, and consider how to improve the structure so that the sub-die can punch several kinds of fins.

3 mold structure design and improvement points

3.1 Layout

There are 4 steps in the layout design (including cut off). That is, the triangular notch, the punching, the flanging and turning feet, and the cutting, 53mm is a step; refer to the layout of the die design manual and the design of the edging part in the fourth part of the mold manual, and the dimensions of the sides are It is determined to be 2.5mm, the width of the steel strip is 113mm; the punching material is Q235-A, and the material thickness is ≤0.5mm. As can be seen from the layout drawing shown in Fig. 2, the layout of the mold is straight, and there is no edge between the parts, which is characterized by material saving. Moreover, the discharge of the scrap and the parts are separated during the punching process, which facilitates the sorting of waste and parts. In addition, because the outer side of the die is the cutting edge, the parts are taken out from one side of the machine tool. Even if it is collected, the machine can be installed outside the stamping equipment in combination with the product features of our factory to realize the automation of punching and wearing.
(1) The working process of the mold.

*Step, the strip is fed by the automatic feeding device, enters through the baffle 18, and the triangular edge is punched out by the side edge 4. It can be seen from the fin layout that the triangular notch of this step is composed of small triangles on both sides of the fin.
The second step is that the circular punch 7, the diamond punch 8 is punched, and the trapezoidal punch 6 cuts out three sides of the six pitch legs.
The third step is that the flange punch 9 is turned out of the circular hole, and the punch 11 is turned out of the pitch foot.
After the zui, the substantially formed part is sent out of the die, the outer edge of the die and the cutter cut the part, and the part falls into the container.

When the unloading plate 5 is working, the strip is pressed, and when the upper mold is ascended, the flanged punch is smoothly withdrawn from the flanged hole, the trapezoidal top core 19, the flanged top core 10, and the top core 16 are pushed out by the spring. The mold is smoothly fed, and four small guides are mounted on the fixed plate 3, passing through the discharge plate 5, and the small guide column enters the concave template guide hole when working. The discharge pole 5 always slides on the small guide post, and the positioning effect is good, and the functions of the protection punches 6 and 11 are also protected.

The mold is mounted on a high-speed punch with an automatic feeding device, and the mold requires high precision and rigidity. Therefore, a four-column ball cage is used. The working parts are made of Crl2MoV steel, the heat treatment hardness is 58-62HBC, the other support parts are made of 45 steel, and the parts with large force such as the discharge plate, baffle plate and top core are used for quenching and tempering treatment with hardness of 45~48HRC.

(2) Improvement points.

The difference in fin pitch is reflected in the flange height of the pitch foot. The first is to consider the trimming of the pitch legs. The trapezoidal punch 6 cuts the three sides of the pitch foot, the spacing is large, and the cut edges are long. The pitch foot is then turned over by the punch 11. At present, there are three kinds of pitch sizes of the X-shaped fins, which are 2.5 mm, 3 mm, and 4 mm, respectively. The difference is O.5mm and 1mm, the size is not much different, then can only cut a large size of Zui, the height is guaranteed by flipping the foot as shown in Figure 4.
After discussion and analysis, two solutions were proposed. One is because the length dimension of the trimming edge is not much different, and the edge trimming is 4mm. The position of the foot is then considered at the desired height on the die. The second is to determine the length of the trimming by controlling the depth of the trapezoidal punch into the concave chopsticks. This method requires high maintenance and commissioning of the mold. It is better to choose the kind of scheme when the length dimension of the trimming edge is not much different.
The problem of sharing the trapezoidal punch is solved, and the next step is to solve the die problem.

From the practice, the experience is summarized, which affects the height of the flanged foot. There are many factors, such as the length of the trapezoidal convex lateral edge, the hardness of the steel strip, the gap between the flanged punch and the die, and the flange on the die. Determination of positional accuracy, etc. Among them, the accuracy of determining the position of the concave flange is the key, and the influence is also large. This factor can be solved by improving the structure.

In practice, we have mastered the law of the change of the height of the flanging, thus determining the positional size of the flanging. There are 4 flip holes on the die, and the space between the flip holes is large. The flip hole portion can be designed as an insert, and the insert is matched with H7/n6. The pitch can be changed by replacing the die insert and the corresponding foot punch, and the fins of different pitches can share a die, and the insert form can also be used to correct the height of the foot.

4 Conclusion

The mold structure is designed reasonably and reduces the input cost of the mold. The proven effect is good, can meet the needs of mass production, has achieved significant economic benefits, and accumulated design experience for other similar situations.

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