Injection molding enables plastics in everyday life to achieve complex shapes and complex details, enabling batch production while maintaining consistent tolerances 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, thus determining the added value of the product, so how to efficiently cool the plastic product in the minimum cycle time, become the design and manufacture of the conformal cooling mold The key considerations in the process, while cooling plays an important role in this.
First, follow the shape cooling to get rid of the traditional way
The principle of conformal cooling is to rapidly reduce the temperature of the plastic part in a uniform continuous manner. 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 from the mold. Any hot spot will delay the injection molding cycle of the molded part, which may cause warpage and dent of the molded part after demolding, and may damage the quality of the surface of the plastic part.
Rapid cooling is carried out by the passage of coolant through the mold to remove the heat of the molded part. The speed and uniformity of this cooling effect is determined by the speed of the fluid passage and the cooling fluid passing through it.
Conventional in-mold cooling channels are achieved by secondary processing. By cross-drilling, the internal network of the straight tube is produced, and the flow rate and direction are adjusted by the built-in fluid plug. This method has its limitations, and the shape of the water network is limited, so the cooling passage is far from the surface of the mold, so that cooling is performed. low efficiency. Not only that, but also the additional processing and assembly time, and the risk that blind channel networks may be blocked. Moreover, in complex cases, in order to reserve the processing of the cooling channels, the mold needs to be cut into several parts to be manufactured, and then spliced ​​into a single piece of mold, which leads to additional manufacturing steps and also shortens the mold. life.
The difference between the conformal cooling method and the conventional cooling method is that the shape of the cooling water passage varies with the shape of the injection molded product, and is no longer linear, as shown in FIG. The cooling water channel solves the problem that the distance between the traditional cooling water channel and the surface of the mold cavity is inconsistent, and the injection molded product can be uniformly cooled and the cooling efficiency is higher.
Figure 1: Schematic diagram of a conventional cooling channel and a contour cooling channel
Second, 3D printing manufacturing
3D printing manufacturing frees people from the limitations of cross drilling. Now, the internal channel can be designed to be closer to the cooling surface of the mold, with smooth corners, faster flow, increased heat transfer to the coolant efficiency; different cooling circuits can be designed according to cooling requirements, designed to achieve consistent speed Heat dissipation to promote uniformity of heat dissipation. The coolant throughput is critical to the cooling rate of the mold. Smooth corners must be designed to reduce pressure loss along the channel.
Metal powder selective melting 3D printing technology can also be produced in cooling channels as small as 1.4 mm in diameter. A beneficial benefit of the powdered 3D printing manufacturing technique is that the powder melts a slightly textured surface that increases the surface area of ​​the cooling contact, resulting in better heat transfer, thereby increasing cooling efficiency and A small turbulence in the channel is formed, thereby achieving the effect of self-cleaning of the channel.
Third, the added value of 3D printing on injection molding products
With the conformal cooling injection mold made by 3D printing, it is possible to achieve injection mold processing efficiency of up to 70%. In the example shown in Fig. 2, the mold of an ice scraper is processed by the additive manufacturing method, so that the injection time is reduced from 80 seconds to 40 seconds, which means that the production speed of the injection molded part is twice as large.
Figure 2: Ice scraper with shape cooling mold
Other major advantages of conformal cooling molds manufactured by additive manufacturing include the ability to form more uniform plastic articles, zero defects in the article, and avoid dents due to uneven 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 in the manufacture of complex molds, additive manufacturing methods are faster than conventional methods due to reduced cooling channel processing and splicing.
It should be noted that the surface quality of the mold produced by the additive is not high, and the required surface precision is obtained by post-finishing and polishing. At this stage, traditional machining and complementary manufacturing advantages complement each other.
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