Injection molding cooling system example
The design of an injection molding cooling system must be customized based on the specific characteristics of the plastic part and production requirements. Different types of plastic parts (such as thin-walled parts, thick-walled parts, and parts with complex structures) place significantly different demands on the cooling system. Proper cooling system examples can provide a reference for the design of similar products, helping engineers quickly grasp the key design points and optimization directions for the cooling system. The following will detail the cooling system design solutions, key parameters, and practical application results for different plastic parts using several typical examples.
The cooling system for a thin-walled electronic housing plastic part demonstrates the design principles for efficient and rapid cooling. This part, a mobile phone housing, is made of ABS, has a wall thickness of 1.2 mm, and measures 150 mm × 70 mm × 8 mm. The required molding cycle time is 30 seconds or less. The cooling system utilizes a conformal parallel cooling circuit. Four 8mm diameter cooling channels are located in the mold cavity and core, with the channel center positioned 15 mm from the cavity surface (approximately 1.8 times the channel diameter) to ensure uniform cooling. Industrial water is used as the cooling medium, with an inlet temperature of 20°C, an outlet temperature of 28°C, and a flow rate of 2 m/s (Reynolds number approximately 5000, indicating turbulent flow). To enhance cooling at corners, circular water wells with a diameter of 6 mm and a depth of 10 mm are installed at the four corners of the part, connecting to the main water channel. In actual production, this cooling system controls the cooling time of plastic parts within 15 seconds, and the temperature difference between different parts of the plastic parts is ≤3°C, effectively avoiding warping and shrinkage defects, and the qualified rate reaches more than 99%.
The cooling system for thick-walled plastic containers demonstrates a gradient cooling design for thick-walled parts. The part is a 5L plastic barrel made of HDPE, with a 5mm wall thickness and an 8mm bottom thickness. The required deformation is ≤0.5mm. Due to the thick wall thickness, a combined system combining serial cooling and localized enhanced cooling is employed. The main water channel has a diameter of 12mm and is evenly distributed around the barrel, with a total length of 3.5m. Three 10mm diameter spray pipes are installed at the bottom, extending 15mm into the bottom to provide direct forced cooling of the thick-walled areas. The cooling medium is a water-ethylene glycol mixture (1:1 ratio) with an inlet temperature of 15°C. Temperature control valves control the flow rate of the medium in different zones, with a flow rate of 1.5m/s in the barrel area and 3m/s in the bottom spray pipes. To monitor the cooling effect, six temperature sensors are installed on the mold to monitor the cavity surface temperature in real time, ensuring that the temperature of the thick-walled areas drops from the molten state (approximately 200°C) to the demolding temperature (approximately 40°C) within 60 seconds. In actual application, this cooling system shortens the overall cooling time of plastic parts to 80 seconds, and controls the bottom deformation within 0.3mm, meeting the use requirements.
An example of a cooling system for a complex automotive plastic part demonstrates cooling optimization solutions for special-shaped parts. This part, a dashboard frame made of PP and 30% glass fiber, features a complex structure consisting of multiple 2mm thick ribs, 10mm high bosses, and recesses, with a maximum size of 300mm × 200mm × 50mm. The cooling system utilizes independently controlled cooling circuits, dividing the part into three zones: edge, center, and rib. Each zone is equipped with independent cooling channels and temperature control. The edge channels have a diameter of 10mm and a center spacing of 25mm; the center channels have a diameter of 8mm and a center spacing of 20mm. The ribs utilize thin 4mm diameter channels, located close to the rib base. Beryllium copper inserts are used to enhance heat transfer (Berylium copper has a thermal conductivity of 200W/(m · K) , significantly higher than the 40W/(m · K) of standard mold steel ). The cooling medium inlet temperature is set for each zone: 25 °C at the edges, 22 °C in the center, and 20 °C at the ribs. Diverter valves control the flow rate to each zone. In actual production, this system effectively solves the problem of uneven cooling in complex structures, keeping the cooling time difference within 5 seconds for each part of the plastic part, and achieving CT7- level dimensional accuracy , meeting the assembly requirements of automotive parts.
The cooling system for a small, multi-cavity plastic part demonstrates the balanced cooling design approach. The part is a USB port housing made of PBT, with a single cavity measuring 10mm × 5mm × 3mm. The mold has 16 cavities, and the weight variation between cavities must be ≤1%. The cooling system utilizes a symmetrical parallel cooling circuit. A 10mm diameter annular main channel surrounds the main channel. Two 6mm diameter branch channels extend from the main channel to each cavity. The branch channel lengths are strictly controlled within ±0.5mm to ensure consistent cooling conditions across cavities. The cooling medium is pure water at an inlet temperature of 22°C. A flow balancing valve regulates the flow rate in each branch channel to maintain a ≤5% variation in cooling medium flow within each cavity. To improve cooling efficiency, the mold utilizes a water-cooled plate structure, with both the cavity and core embedded within the plate. The water channels within the plate are arranged in a grid pattern to enhance overall heat dissipation. In actual production, this cooling system keeps the cooling time of plastic parts in 16 cavities within 8 seconds, with a weight difference of ≤0.8%. The production efficiency reaches 12,000 pieces per hour, meeting the needs of mass production.
The cooling system for high-temperature engineering plastics illustrates the cooling design for specialized materials. This plastic part, an aerospace connector, is made of PEEK (polyetheretherketone), with a melt temperature of 380°C. It requires extremely high dimensional stability and mechanical properties. The cooling system utilizes a high-temperature-resistant cooling circuit. The waterway is constructed of 8mm diameter 316 stainless steel (high-temperature corrosion-resistant) with a polished surface (Ra ≤ 0.8μm) to reduce scaling. High-temperature thermal oil (operating at 150°C) is preheated by a heating device before being passed into the mold, achieving “reverse cooling” (i.e., slowly cooling from a high temperature) to avoid internal stress in the PEEK caused by rapid cooling. The cooling circuit utilizes a spiral arrangement to create a uniform temperature field around the mold cavity. The cooling medium flows at a rate of 1m/s, with a controlled temperature differential between the inlet and outlet of 3°C. High-precision thermocouples (with a measurement accuracy of ±0.5°C) are installed in the mold to provide real-time cavity temperature feedback. A PID control system regulates the medium flow and temperature. In actual applications, this cooling system controls the cooling time of PEEK plastic parts within 120 seconds, and the internal stress test results show that the stress value is ≤5MPa, meeting the stringent requirements of the aerospace field.
