To ensure the uniform mold temperature during the cooling process of injection molding machines, first, optimize the design of cooling channels, including reasonable layout, determination of appropriate parameters and adoption of conformal cooling technology. Second, control and regulate the cooling medium, paying attention to flow distribution and temperature stability. Third, optimize the mold materials and structure, select suitable materials and improve the structure to enhance the heat dissipation effect.
Optimization of Cooling Channel Design
1.Reasonable Layout of Cooling Channels
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Principle of Even Distribution:
Cooling channels should be distributed as evenly as possible around the mold cavity. For example, for a rectangular mold cavity, the cooling channels can be designed to be arranged at equal distances around the cavity, so that the cooling rates in all directions of the mold tend to be the same. If the mold is circular, the cooling channels can adopt an annular or spiral layout to ensure that heat is evenly dissipated from the center to the edge of the mold.
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Avoiding Cooling Dead Zones:
Attention should be paid to the possible cooling dead zones in the mold, such as some deep holes, narrow grooves or complex internal structures. For these areas, special cooling channel branches can be designed or insert cooling methods can be adopted. For example, in the mold for injection molding products with deep holes, separate cooling channels can be designed at the core parts corresponding to the deep holes, or inserts with cooling pipes can be used to ensure that these parts can also be effectively cooled.
2.Determination of Appropriate Channel Parameters
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Channel Diameter:
The diameter of cooling channels is generally between 6 – 12 mm. Larger diameter channels can allow more cooling medium to pass through, which helps to carry away more heat, but may lead to a less compact mold structure. Smaller diameter channels may increase the flow resistance of the cooling medium and affect the cooling efficiency. It is necessary to comprehensively determine it according to factors such as the size of the mold, the size and material of the injection molded product.
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Channel Spacing:
The channel spacing is usually between 2 – 5 times the channel diameter. Appropriate spacing can ensure that the cooling medium can effectively cover the surface of the mold cavity and avoid local overheating or overcooling. For example, for the mold of products with thick walls and materials with low thermal conductivity, the channel spacing can be appropriately reduced to enhance the cooling effect.
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Distance between the Channel and the Cavity:
The distance between the cooling channel and the surface of the mold cavity is also crucial. Generally, this distance should be between 1 – 3 times the channel diameter. If the distance is too close, it may lead to excessive temperature fluctuations on the mold surface, and if it is too far, the cooling efficiency will be reduced.
3.Adoption of Conformal Cooling Technology (for Complex Molds)
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Principle and Advantages:
Conformal cooling channels are designed according to the shape of the mold cavity, which can better fit the mold surface, so that the flow path of the cooling medium in the mold matches the heat dissipation path. This technology is very effective when injecting products with complex curved surfaces or irregular shapes. For example, in the mold for automotive interior parts, conformal cooling channels can be arranged along the complex contours of the interior parts, greatly improving the uniformity of cooling and reducing the warpage deformation of products caused by uneven cooling.
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Design and Manufacturing Methods:
The design of conformal cooling channels requires the help of advanced computer-aided design (CAD) software. The best shape of the cooling channels is generated through the three-dimensional modeling of the mold cavity. In terms of manufacturing, 3D printing technology or special mold processing techniques can be used to achieve it. 3D printing can manufacture molds with complex internal structures, including high-precision conformal cooling channels.
Control and Regulation of Cooling Medium
1.Even Distribution of Flow Rate
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Use of Flow Control Valves:
Install flow control valves on each branch pipe of the cooling system. The flow rate of the cooling medium in different channels can be controlled by adjusting the opening degree of the valves. The flow rate can be reasonably distributed according to the cooling requirements of different parts of the mold. For example, for the areas with concentrated heat in the mold, the flow rate of the cooling channels in this area can be appropriately increased, so that the cooling medium can carry away heat more quickly.
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Design of Manifolds and Dividers:
Set manifolds and dividers in the cooling system. The manifold is used to evenly distribute the cooling medium to the inlets of each cooling channel, and the divider is used to collect the cooling medium flowing out of each channel. This design can reduce the problem of uneven flow rate caused by differences in pipe resistance.
2.Stable Temperature Control
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Selection and Maintenance of Refrigeration Equipment:
Select appropriate refrigeration equipment to control the temperature of the cooling medium. For large-scale injection molding production, industrial chillers may be needed to provide a stable low-temperature cooling medium. Regular maintenance of refrigeration equipment should be carried out, including cleaning the condenser, checking the pressure and content of the refrigerant, etc., to ensure its refrigeration efficiency and temperature control accuracy.
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Temperature Sensors and Feedback Control:
Install temperature sensors at the inlets and outlets of the cooling medium and at the key parts of the mold to monitor temperature changes in real time. Through the feedback control system, the operating power of the refrigeration equipment or the flow rate of the cooling medium can be adjusted according to the signals from the sensors, so that the mold temperature is kept within the set range. For example, when the sensor detects that the temperature of a certain part of the mold is too high, the feedback system can automatically increase the flow rate of the cooling medium in the cooling channels of this area or reduce the temperature of the cooling medium.
Optimization of Mold Material and Structure
1.Selection of Appropriate Mold Materials
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Preference for Materials with High Thermal Conductivity:
Choosing mold materials with high thermal conductivity can improve the heat transfer efficiency and make it easier for the mold temperature to be uniform. For example, copper alloy mold materials have a much higher thermal conductivity than ordinary steel. When injecting products with high requirements for temperature control (such as optical lenses), copper alloy molds can be considered. However, copper alloy materials are relatively expensive, and their mechanical properties may not be as good as steel, so a comprehensive trade-off is needed.
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Uniformity of Materials:
Ensure the quality uniformity of the mold materials themselves, and avoid differences in heat conduction caused by the non-uniform internal structure of the materials. When purchasing mold materials, choose reliable suppliers and conduct inspections on the materials to prevent problems such as impurities and pores inside the materials.
2.Improvement of Mold Structure
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Design of Heat Conduction Structures:
Some heat conduction structures, such as heat sinks or heat bridges, can be designed inside the mold. Heat sinks can increase the contact area between the mold and the cooling medium and accelerate heat dissipation. Heat bridges can guide the heat in the areas with concentrated heat in the mold to the areas with good cooling effects. For example, heat sinks can be designed at the core part of the mold. When the internal structures of injection molded products (such as plastic columns) are in contact with the core, heat can be transferred to the cooling medium more quickly through the heat sinks.
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Symmetrical Design of the Mold (if applicable):
For the molds of some symmetrical products, adopting a symmetrical mold structure can make the cooling process more uniform. For example, for the mold of a symmetrical plastic box, the cooling channels, mold wall thickness and other structures can be designed symmetrically, so that the heat dissipation and temperature changes on both sides of the mold will be more consistent during the cooling process.
