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Plastic Mold Cooling With The Future Needs 1500 Metal 3D Printers
May 30, 2018

Core Tip: According to relevant data, it was discovered that the technology of conformal cooling of plastic injection molds was first proposed by Professor Sachs of the Massachusetts Institute of Technology in 1997. He believes that this technology will be one of the four main applications of 3D printing. After 3D printing technology has been developing continuously for 20 years, the scale application of the technology in the mold industry has also been confirmed. According to Antarctic Bears, in some mold manufacturers, the current cooling mold business has accounted for 40% of the total business.

 According to related data, the technology of conformal cooling of plastic injection molds was first proposed by Professor Sachs of the Massachusetts Institute of Technology in 1997. He believes that this technology will be one of the four major applications of 3D printing. After 3D printing technology has been developing continuously for 20 years, the scale application of the technology in the mold industry has also been confirmed. According to Antarctic Bears, in some mold manufacturers, the current cooling mold business has accounted for 40% of the total business.

 

    "In the next 10 years, China's mold industry needs 1,500 metal 3D printers."

 

    The conformal cooling method of the injection mold is different from the traditional cooling method. The shape of the cooling water channel changes with the shape of the injection molding product, and is no longer a traditional straight line. The 3D printing technology can avoid the limitation of cross-drilling in the manufacture of the cooling water circuit. The 3D-printed conformal cooling water circuit can also be designed with different cooling circuits according to the cooling requirements, so as to dissipate heat at a uniform speed to promote uniform heat dissipation. Sex.

 

    For mold manufacturers, because the quality of the mold directly determines the injection molding production efficiency, and determines the product quality, which determines the added value of the product, so how to efficiently cool the plastic products in the minimum cycle time, become a conformal cooling injection mold design With the key considerations in the manufacturing process, cooling plays an important role during this period.

 

    The principle of conformal cooling is that in a uniform and continuous manner, the temperature of the plastic part is rapidly lowered, the injection molded part cannot be taken out of the mold during the cooling process until the cooling is sufficient, and then the injection molded part is taken out of the mold. Any hot spot delays the injection molding cycle, which may cause warpage and dents in the molded part after demolding, and may damage the surface quality of the plastic part. Rapid cooling is achieved by the cooling fluid passing through the channels in the mold to remove heat from the injection molded part. The speed and uniformity of this cooling effect is determined by the fluid passage and the speed through which the cooling fluid passes.

 

    In a conventional mold, the cooling water circuit creates an internal network by cross drilling and adjusts the flow rate and direction through a built-in fluid plug. The application of metal 3D printing technology in the manufacture of mold cooling waterways has overcome the limitations of cross-drilling methods on cooling water circuit design. Mold design companies can now design the contoured waterways closer to the mold's cooling surface, with smooth corners, faster flow, and higher cooling efficiency.

 

    The traditional cooling channel inside the mold is achieved through secondary processing. Through cross-drilling, the internal network of the linear tube is generated, and the flow rate and direction are adjusted by the built-in fluid plug. This method has its limitations. The shape of the water network is limited. Therefore, the cooling channel is far from the surface of the mold, so that the cooling low efficiency. Not only that, but also had to face additional processing and assembly time, and the risk that the blind spot's network of channels might be blocked; and, in a complicated situation, in order to reserve the processing of the cooling channels, the mold needs to be divided into several Partially manufactured and then spliced into a single piece mold, which leads to an additional manufacturing process, and will also shorten the life of the mold.

 

    The difference between the conformal cooling method and the traditional cooling method is that the shape of the cooling water channel changes along with the shape of the injection molded product and is no longer a straight line. This type of cooling water channel is a good solution to the distance between the traditional cooling water channel and the mold cavity surface. Inconsistent problems can result in uniform cooling of injection molded parts and better cooling efficiency.

 

    3D printing manufacturing frees people from the limitations of cross drilling. Now, it is possible to design the inner channel closer to the cooling surface of the mold, with smooth corners, faster flow, and increase the efficiency of heat transfer to the cooling liquid; different cooling circuits can also be designed according to the cooling requirements, aiming at consistent speed Heat dissipation to promote heat dissipation uniformity. Coolant throughput is critical to the mold's cooling rate, and smooth corners must be designed to reduce the pressure loss along the passage.

 

    It is reported that metal powder selective laser melting (SLM) 3D printing technology can also be produced in cooling channels down to 1.4 mm in diameter. One of the advantages of the powdered 3D printing manufacturing technology is that the powder melting brings a slightly textured surface, this texture structure increases the surface area for cooling contact, brings about better heat transfer effect, thereby improving cooling efficiency and forming a channel Small turbulence inside, so as to achieve the channel self-cleaning effect. Conformal cooling injection molds made by 3D printing can increase the injection molding efficiency by 70% or more. For example, an ice scraper mold can be processed by an additive manufacturing method, which can reduce the injection cycle from 80 seconds to 40 seconds. This means that the production speed of injection molded parts doubles.

 

    The other major advantages of conformal cooling molds manufactured by additive manufacturing include the ability to form more uniform molded parts, zero defects in the products, and avoiding dimple marks due to non-uniform cooling rates. In addition, when developing new injection molding products, it helps to achieve new product development with less iterations.

 

    Of course, more advantages include: When manufacturing complex molds, the additive manufacturing method is faster than the conventional method due to the reduction of the processing and stitching of the cooling channels.

 

    It should be noted that the additive-manufactured mold does not have high surface accuracy, and the required surface accuracy is obtained by the later finishing and polishing processes. In this link, traditional machining and additive manufacturing complement each other.

 

    In 2007, Shi Yusheng and Wu Zhigang proposed the design method of the conformal cooling channel based on the discrete/aggregate model. The heat transfer model of the cooling channel with circular, elliptical, semi-oval and U-shaped cross-sections was established and used. Laser sintering (SLS) technology successfully manufactured the incense box mold.

 

    The cross-sectional shape of the cooling water channel processed by the 3D printing method is diverse, and may be U-shaped, circular, elliptical, or the like. With the use of SLM molding process, 3D printing is used for conformal cooling water passages. Circular section is adopted for the cross section. This not only can reduce the thermal stress accumulation at the edges and corners, but also can avoid mold damage caused by stress concentration during injection molding, and can also accurately refer to traditional injection molding. The design experience of the mold cooling waterway, better control the wall temperature of the mold. The cooling of an impeller plastic part can be divided into two parts: the end face and the blade. The specific cooling scheme is as follows:


    (1) Cavity cooling scheme.

 

    Scheme 1, the diameter of the cooling water channel is 3mm, and the pipeline has 1 inlet and 1 outlet, as shown in Figure 2a.

 

    In Option 2, the diameter of the cooling water channel is 4mm, and the overall shape of the cooling water channel is a ring, as shown in Figure 2b.

 

    Scheme 3, the diameter of the cooling channel is 3mm, the pipeline has 3 inlets and 3 outlets, as shown in Figure 2c.

 

    In Scheme 4, the diameter of the cooling channel is 4mm, and the overall shape of the cooling channel is rectangular, as shown in Figure 2d.

 

    (2) Core cooling.

 

    Solution A, the diameter of the cooling channel is 6mm, and the overall shape of the cooling channel is a ring, as shown in Figure 2e.

 

    Solution B, the diameter of the cooling channel is 6mm, and the overall shape of the cooling channel is rectangular, as shown in Figure 2f.

 

    A software Moldflow is used in the random cooling pre-design. Moldflow is a professional injection molding CAE software with powerful functions. It is widely used in mold injection analysis in the field of injection molding. Moldflow 2014 version can be used for the design of conformal cooling waterways, with powerful design and optimization capabilities. In the future, with the continuous development and application of 3D printing technology, conformal cooling technology will gradually become a hot spot for the research of injection mold cooling systems. The use of 3D printing technology to manufacture conformal cooling molds not only simplifies the machining process, but also facilitates the design of conformal cooling waterways, and improves the design efficiency to make the cooling water channel more conformable.