Application of 3D printing mold conformal waterway technology in hot runner mold

As we all know, mold, as the “mother of industry”, is an important cornerstone of manufacturing. The advancement of mold technology can effectively enhance the core competitiveness of enterprise groups and key industries in the country. In order to meet the needs of consumers, companies continue to innovate and strictly control product quality. With the acceleration of product upgrades, the production efficiency and quality of new products are particularly important, and the requirements for molds have also increased.At present, mold companies often encounter technical bottlenecks in terms of product deformation and injection molding cycle. They cannot fully meet the needs of product development through mold modification and other means. In the end, they can only compromise by changing product design intentions, which leads to new

1 Introduction

As we all know, mold, as the “mother of industry”, is an important cornerstone of manufacturing. The advancement of mold technology can effectively enhance the core competitiveness of enterprise groups and key industries in the country. In order to meet the needs of consumers, companies continue to innovate and strictly control product quality. With the acceleration of product upgrades, the production efficiency and quality of new products are particularly important, and the requirements for molds have also increased. At present, mold companies often encounter technical bottlenecks in product deformation and injection molding cycle. They cannot fully meet the needs of product development through mold modification and other means. In the end, they can only compromise by changing product design intentions, which leads to a long new product development cycle. , It also makes the appearance and structure not fully meet the needs of the market. 3D printing conformal waterway technology is an industrial application of 3D printing technology in the field of molds, which can reduce injection molding cycles by more than 20% and solve quality problems such as burns and deformation caused by uneven cooling and excessive mold temperature. This article uses specific cases to introduce the application of 3D printing mold conformal waterway technology in hot runner molds.

2 Basic principles of 3D printing technology

3D printing (3DP), also known as Additive Manufacturing (AM), is a digitally-driven, new manufacturing method that continuously accumulates processing materials. At present, there are three main manufacturing methods: subtractive manufacturing, iso-material manufacturing and additive manufacturing. Subtractive manufacturing is a process of continuous reduction of materials. The forming of parts is the continuous reduction of materials on the blank, such as turning, milling, planing, grinding, drilling, etc., which is a serious waste of materials. The total amount of materials before and after the production of equivalent materials is basically unchanged, such as casting, forging, welding, etc. Additive manufacturing is an additive process in which materials are formed layer by layer from scratch, and the material utilization rate is close to 100%. It is a green and environmentally friendly new manufacturing method.

The basic principle of 3D printing is from discretization, accumulation to forming: first discretize the parts to be manufactured, cut the three-dimensional data into two-dimensional plane data, and then discretize it into one-dimensional linear data; then the material Extrusion or sintering or melting along the linear data, the linear solid material is piled into a flat solid material, and then piled into a three-dimensional solid material. The entire manufacturing process of 3D printing technology is data-driven. Therefore, the design of the three-dimensional model determines the shape and structure of the final product.

The basic process of 3D printing is to build a three-dimensional model, slice the model layer by layer, and then input the slice data into a 3D printer for layer-by-layer printing, and finally get a product that is exactly the same as the three-dimensional model. At present, the materials available for 3D printing are metal, nylon, resin, ceramics, etc., which are widely used in the fields of molds, medical treatment, automobiles, aerospace, and military industries.

Application of 3D printing mold conformal waterway technology in hot runner mold

Figure 1 3D printing process

3 3D printing technology changes the mold cooling system

3D printing technology can create a conformal waterway that cannot be produced by traditional mold processing methods. It can reduce injection cooling time, reduce deformation of injection molded parts, reduce burns, black clouds and yellow clouds caused by poor cooling effects, and greatly improve the company Production capacity and product quality have important strategic significance for the long-term development of the manufacturing industry.

3.1 Analysis of the influencing factors of product injection cycle and product deformation

Poor temperature control is the main factor for the long injection cycle and product deformation.

(1) The factors that affect the product injection cycle include injection holding time, mold clamping, cooling, mold opening, and so on. Among them, the cooling time is the longest, occupying about 60% to 70% of the entire product injection cycle. Therefore, the reduction of cooling time is an important method to reduce the product injection cycle.

(2) There are many factors that affect product deformation. Among them, the inconsistent shrinkage speed of each part of the product caused by uneven cooling is the biggest factor affecting product deformation. Factors such as the inconsistent cooling speed of the front and rear molds and difficulty in cooling the corners and corners can easily cause different shrinkage rates of each part of the product, resulting in warping, dents and other deformation defects, which affect the appearance of the product and the assembly of the production line.

(3) Factors affecting product burns, black clouds and yellow clouds and other defects are mainly the poor cooling effect of the mold, which causes the maximum temperature to be too high, which exceeds the withstand temperature of the material.

3.2 Conformal waterway

According to the above analysis, a good cooling effect is an important guarantee for optimizing the injection cycle and product quality. Mold cooling mainly relies on the cooling water circuit, so the optimization of the water circuit is the core factor. The traditional waterway can only be processed into a straight line, and the distance from the product is relatively long, and the distance is uneven, so the cooling effect of the product is not optimal. With 3D printing conformal waterway technology, the printed waterway can be of any structural shape and any cross-sectional shape, which can achieve the smallest and most uniform distribution of the waterway in the mold and the product, and achieve the best cooling effect. Figure 2 is a 3D printed conformal waterway, (a) is a waterway insert, (b) shows the position and direction of the waterway in the insert.

At present, the domestic use of 3D printing technology to manufacture conformal waterway inserts has achieved small-scale applications. Some companies are trying to use 3D printing technology to print mold parts to achieve complex internal conformal cooling water channels that cannot be processed by traditional techniques to improve precision molds. Cooling uniformity and efficiency. More and more mold companies and injection molding manufacturers have introduced and continuously optimized 3D printing conformal waterway technology, which has contributed to the technological progress and development of my country’s manufacturing industry.

Application of 3D printing mold conformal waterway technology in hot runner mold

Figure 2 3D printing conformal waterway

4 Combination of 3D printing technology and hot runner technology

Hot runner technology is an excellent means to shorten the injection cycle and save materials. After each injection of the hot runner mold is completed, the runner colloid will not solidify under the heating of the heating device, so the product does not need to be ejected from the runner nozzle when the product is demolded. At the beginning of the next injection cycle, the injection runner is still through. The waste heat is removed in time, the runner system is not limited in cooling, and the cooling time is only affected by the cooling of the product, so the injection cycle is reduced to a certain extent. 3D printing technology can greatly reduce product cooling time, therefore, the combination of hot runner technology and 3D printing technology can further reduce the injection cycle.

The 3D printing conformal water circuit technology can arrange the cooling water circuit near the surface of the product, greatly reducing the cooling time of the product, further reducing the production cycle, and improving the efficiency of the machine. Taking the hot runner mold of the cosmetic transparent cover as an example, Figure 3 shows the design comparison between the 3D printed conformal waterway and the traditional waterway. The water path in the traditional mold (a) cannot fully fit the surrounding position of the product, and the product of this kind of inverted structure has a narrow internal area and the water path cannot be arranged; the water path in the 3D printing conformal water path mold can be designed in a spiral shape. It can be arranged in a small space, and can also be attached to the periphery of the product to achieve uniform and rapid cooling. It can be seen intuitively that the 3D printing conformal waterway design is more reasonable.

Application of 3D printing mold conformal waterway technology in hot runner mold

Figure 3 Comparison of waterway design

The function of 3D printing conformal water circuit is mainly reflected in the reduction of molding cycle. Figure 4 is a comparison of product molding cycle: when using traditional mold cooling water circuit, the time for the part to reach the ejection temperature is 58s, while when using 3D printing conformal water circuit , The time for the part to reach the ejection temperature is reduced to 28s. Calculating based on the mold opening time of 5s, the molding cycle is reduced from 63s to 35s, which is about 48%, indicating that the cooling efficiency of the 3D printing conformal cooling water circuit is greatly improved.

Application of 3D printing mold conformal waterway technology in hot runner mold

Figure 4 Comparison of ejection time

The 3D printing conformal water circuit can greatly reduce the maximum temperature of the mold and the product, and the temperature at each position is extremely uniform. Figure 5 shows the comparison of the mold temperature between the traditional mold and the 3D printing conformal waterway mold. It can be seen that the male mold insert of the traditional mold has a temperature difference of 38°C, while the same male mold insert temperature difference of the 3D printing conformal waterway mold is only 1°C, year-on-year Decrease 37°C. Figure 6 shows the product temperature comparison. It can be seen that the product temperature difference at the male mold insert of the traditional mold is 47°C, while the product temperature difference at the male mold insert of the 3D printing conformal waterway mold at the same position is 13°C, a year-on-year decrease of 34°C. The comparison between the mold temperature and the product temperature indicates that the cooling uniformity of the 3D printing conformal water circuit is excellent.

Application of 3D printing mold conformal waterway technology in hot runner mold

Figure 5 Mold temperature comparison

Application of 3D printing mold conformal waterway technology in hot runner mold

Figure 6 Product temperature comparison

The uniform cooling effect greatly reduces the shear heating effect, and can produce more products in one mold without deformation. The traditional mold manufacturing cosmetic transparent cover can only guarantee the product quality of one mold with four holes, and the continued increase of the hole will cause serious product deformation due to problems such as poor cooling. With the use of 3D printing conformal waterway technology, the quality can be increased from a four-cavity mold to a sixteen-cavity mold, and the injection cycle is reduced by about 48%, so the overall production capacity can be increased by about five times. Figure 7 (a) is a sixteen-cavity mold, and (b) is the product.

Application of 3D printing mold conformal waterway technology in hot runner mold

Figure 7 One mold with sixteen holes

5 concluding remarks

3D printing is a green and environmentally friendly data-driven additive manufacturing technology. The application of 3D printing in the mold field is a major breakthrough in mold technology and has extremely important practical significance. Application examples of 3D printing technology on hot runner molds show that 3D printing technology can produce mold inserts with conformal water channels, ensuring uniform and rapid injection cooling, shortening the injection molding cycle by about 48%, and reducing the risk of plastic parts deformation. While improving the quality of plastic parts, the production capacity can be increased several times by increasing the number of mold holes.

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