## 4 Cooling System Design and Cooling Simulation Based on UG and Moldflow
### Selecting the Proper Type of Conformal Cooling Channels for Thin-Wall Products
#### 4.2.1 Design Principles and Specifications of Cooling Channels  
Effective cooling channel design for injection molding often involves dividing the mold into several geometrical features, with separate channels designed and laid out for each feature. These features are then combined to form the complete cooling system for the injection molding process. In order to balance mold manufacturing and plastic part production costs, injection cooling system molds typically use a combination of straight-through and shaped cooling channels. Conformal cooling channels are mainly used for complex curved features of plastic parts or for deep cavity features where conventional cooling channels cannot achieve the cooling effect. Additionally, conformal cooling channels are often utilized for injection molds with moving parts and complex ejection systems.  
The layout of cooling channels in molds is often limited by the mold's intricate surface features and complex structure. As shown in Figure 8, a conventional pipeline model is shown. The channels are all the straight-drilled type. In practice, the design of cooling channels cannot always be achieved according to the ideal design scheme due to these limitations. As a result, mold designers need to have the expertise to continually modify the plastic part to match the shape, size, wall thickness, and structural characteristics of the cooling water channels. This requires a deep understanding of the manufacturing process and the ability to optimize the design of cooling channels to ensure optimal performance of the mold. The cooling channel design principles and specifications are as follows. Figure 9 displays the local geometric configuration of conformal cooling channels, which exhibit a more complex shape that conforms closely to the shape of the product.  
Figure 7: The model of the mold with simple spiral cooling channels.  
(1) The distance between the centerline of the cooling channel and the cavity wall is a critical consideration in mold design. When the product thickness is uniformly distributed, it is essential to maintain a consistent distance between the cooling channel's centerline and the cavity wall throughout. However, when the product thickness is unevenly distributed, it is necessary to decrease the distance between the cooling channel's centerline and the cavity wall in the thicker areas to ensure that the product cools uniformly. This is particularly important to prevent warpage and deformation and to achieve the desired product quality. Therefore, careful consideration of the cooling channel layout is crucial to achieve optimal mold performance and to ensure consistent product quality.  
(2) Cooling channel layout: There are two types of layouts, namely series and parallel layouts. When cooling channels are connected in series, the coolant flow rate remains basically unchanged, but under the complex cooling channel layout, the channel loss value and pressure drop are larger. When cooling channels are connected in parallel, the flow rate in each branch cooling channel is different, resulting in uneven cooling of plastic parts. Therefore, in order to avoid encountering the problems of the parallel connection method, the series layout method should be given priority.  
Figure 8: Model of the mold with conventional cooling channels.  
Figure 9: Local geometric configuration of conformal cooling channels.  
(3) Cooling channel length: increasing the length of the cooling channel will increase the heat transfer area of the channel, and when using a series cooling channel in a series layout, the longer channel may lead to an excessive pressure drop of the coolant; therefore, the channel length should not be too long.