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Conformal Cooling Injection Mold Based On 3D Printing
Jun 11, 2018

Core Tip: Injection molding enables plastic products in daily life to obtain complex shapes and intricate details, and achieves batch production while maintaining a stable tolerance range and maintaining a high-quality product surface.

 Injection molding enables plastic products in daily life to obtain complex shapes and intricate details, and achieves batch production while maintaining a stable tolerance range and maintaining a high-quality product surface.

 

        For mold manufacturers, because the quality of the mold directly determines the efficiency of injection molding, and determines the quality of the product, which determines the added value of the product, so how to efficiently cool the plastic product in the minimum cycle time becomes the design and manufacture of conformal cooling mold The key considerations in the process, and cooling played an important role during this period.

 

First, with the form of cooling from the constraints of the traditional way

 

        The principle of conformal cooling is to rapidly lower the temperature of a plastic part in a uniform and continuous manner. The injection molded part cannot be taken out of the mold during cooling until it is cooled sufficiently, and then the injection molded part is taken out from 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 passage of coolant through the channels in the mold, which removes the heat from the 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.

       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 channel network might be blocked. Moreover, in the complicated case, in order to reserve the processing of the cooling channel, the mold also needs to be cut into several parts to make, and then spliced into a whole piece of the mold, which leads to an additional manufacturing process, and also shortens the mold life.

 

        The difference between the conformal cooling method and the traditional cooling method is that the shape of the cooling water passage changes with the shape of the injection molded product, and is no longer linear, as shown in FIG. 1 . This kind of cooling waterway solves the problem that the distance between the traditional cooling waterway and the mold cavity surface is inconsistent. It can make the injection molding product get uniform cooling and the cooling efficiency is higher.

 

Second, 3D printing manufacturing

 

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

 

         Metal powder selective melting 3D printing technology can also be produced in cooling channels down to 1.4 mm in diameter. A beneficial advantage of the powdered 3D printing manufacturing technique 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 Small turbulence in the channel is formed to achieve the self-cleaning effect of the channel.

 

Third, the added value of 3D printing to injection molding products

 

        With the conformal cooling injection mold manufactured by 3D printing, the injection mold processing efficiency can be as high as 70%. In the example shown in Fig. 2, an ice squeegee mold is processed by an additive manufacturing method, which reduces the injection time from 80 seconds to 40 seconds, which means that the production rate of injection molded parts is doubled.

 

Figure 2: Ice scraper with cooling die

        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 shrinkage marks due to non-uniform cooling rates. In addition, when developing new injection molding products, it helps to achieve product development with fewer iterations. Of course, more advantages include the fact that 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 precision of the mold surface produced by the additive is not high, and the required surface precision is obtained through the later finishing and polishing processes. In this link, traditional machining and additive manufacturing complement each other.