Shortening material retention time is the core tec

2022-06-23
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Shortening the material retention time is the core technology of the die head.

in the hot forming process of plastic films and plates, product quality problems caused by polymer degradation are often encountered. Once the raw material is degraded, its mechanical properties will generally change, such as the disappearance of elasticity, the decrease of strength, the increase of viscosity and so on. The visual representation of the product, such as yellowing and black spots (coke), the products at both ends are easy to crack and break edges. After degradation, some materials will gradually accumulate in the mold cavity and adhere to the surface of the mold cavity, or even block the mold cavity, affecting the normal production of the product. Shortening the residence time of materials in the mold cavity and reducing the risk of material degradation are of innovative value for producing high-quality products, prolonging the production cycle and reducing costs

specific case

generally, if the retention time is too long, the material will adhere to the mold cavity after degradation, especially at the shunt of clothes hanger channel and the two ends, it is easy to accumulate. As shown in Figure 1, there is obvious material retention and carbonization in the flow channel. If the raw material stays at the end of the flow channel for a long time, the characteristics of the raw material will change, and the edge of the product is easy to crack. In view of the above problems in the production process, the designer must consider shortening the residence time of materials to further improve and optimize the flow channel of the flat die. It can minimize the residence time of materials in the mold cavity, improve the product quality and the stability of continuous production

at present, the most common extrusion flat die runner designs in the market include hanger type and branch type. Now I will share and discuss with you the comparison of simulation calculation and analysis data before and after the improvement. From the pressure distribution of the material flow, shortening the residence time and obtaining uniform velocity data, the coat hanger channel design is undoubtedly the best choice. However, not all die hanger runner designs are the best design scheme. Because the middle runner and the runner at both ends of the hanger runner design are the same, this is also the included angle design of the reason why it can not become the mainstream material in the society

for the die head with relatively wide width, the width l of the die body needs to be very wide to meet the layout of the clothes hanger channel design. Secondly, as the middle channel is relatively close to the end face of the feed inlet, the distance from the clothes hanger diversion to the die lip outlet becomes very long. The arrangement of the fastening screws of the die body at the middle position is relatively backward, l0 is very short, L1 is very long, and the die body will expand and deform under the action of extrusion pressure, Because of the deformation of the whole mold cavity, the channel parameters have changed greatly. The final result is that the uniformity and pressure of the material flow are completely inconsistent with the design parameters. So is there a more reasonable runner design that can meet the die strength design of wide width extrusion flat die? 1. Is economic transformation and development effective in shortening the residence time of materials

for this reason, we have done a lot of simulation research and data analysis on the advantages of high efficiency, energy saving and high cost performance ratio, and achieved some results. An improved and optimized branch pipe runner design has a surprising performance

optimization solution

next, take the casting film die with an effective discharge width of 3500mm as an example, simulate the production of raw material CPE, with an extrusion capacity of 1500kg/h for simulation calculation and analysis, and analyze and compare the previous standard branch pipe runner design with the improved and optimized branch pipe runner design

the early branch flow channel can be designed to obtain reasonable extrusion pressure and uniform flow rate. The disadvantage is that the raw materials stay at the end of the channel for a long time, which is not conducive to long-term production, and the probability of defects in end products is high. After optimizing the design of branch flow passage, we can be surprised to find that all design parameters tend to be more reasonable

after improvement and optimization, the residence time of the materials in the branch channel is shortened from 193 seconds required in the original design to 39 seconds now, which has been greatly shortened, and further solves the product defects caused by material retention. In the final analysis, the innovation priority put forward by Jingcheng should focus on the actual needs of customers, and has been exploring the causes of product defects in plastic film and sheet extrusion and relevant solutions. Provide the best die head customized design scheme for continuous and long-term stable production, and create value for end users to reduce production costs

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