Injection molding cycle time is a crucial component in the efficacy of your injection molding process, and hence a huge influence on the cost and bottom-line consequences of any Bucket Mould Manufacturer project you undertake. In short, the faster your cycle time (while keeping an acceptable degree of quality), the more components you can make with less machine time and the cheaper your overall expenses.

　　While the injection molding cycle time is a significant contributor to your company’s overall performance, it is a procedure that should not be rushed. This article aims at providing a deeper understanding of the injection molding cycle and how injection mold cooling affects the overall outcome of the process.

　　COOLING SYSTEM AND COOLING TIME IN INJECTION MOLDING

　　Cooling time is an essential aspect of the injection molding cycle that consumes the majority of the cycle time. It has a significant impact on the end product/ service, and it is not an aspect where you should joke around taking shortcuts. Adequate cooling time is not just important for part quality; it is also the most time-consuming element of an injection molding cycle.

　　Cooling typically accounts for 80 to 85 percent of total cycle time. When you realize that the cooling portion of the cycle is the inverse of the enormous amount of heat necessary to liquefy the plastic resin during the injection process, the 80+ percent figure sounds reasonable.

　　INJECTION MOLDING PROCESS

　　Let’s take a look at the cooling process as part of the whole injection molding cycle to see why it’s so important:

　　Heating of resin: The base resin is heated to temperatures that liquefy it and takes it to the proper viscosity and mass flow for injection during this initial stage.

　　Injection: The hot mixture is poured into the cavity or cavities of the mold.

　　Packing and holding: Injection continues as some of the previously injected material cools and shrinks. The pack/hold stage injects extra material into the cavity to ensure that it is filled, and then “holds” the material in place to prevent backflow.

　　COOLING SYSTEM IN INJECTION MOLDING PROCESS

　　After the above step is complete the cooling system then takes up its work in the following process;

　　Cooling: The cooling stage is deemed to have commenced once the packing/holding stage is completed. Although the material starts to cool as soon as it leaves the heating injection nozzle and penetrates the mold cavity, cooling time should only be determined after packing and holding. The liquefied resin begins to re-solidify and take on the shape of the mold cavity at this time.

　　Ejection: Once the material has cooled and set enough to keep its shape, the part can be expelled using the mold ejector pins.

　　Quality control: Parts are inspected on-site to ensure appropriate manufacture and quality. Inadequate cooling time can result in part faults and rejections, which we will discuss momentarily.

　　The shortest achievable cooling time will be determined by how quickly heat can be transmitted at each stage of its journey; thus, the shortest achievable cooling time will be determined by the slowest stage. Because plastic is a poor thermal conductor, the first stage represents a bottleneck in the transfer of heat; the only method to speed up heat conduction is to lower the cavity wall temperature.

　　Cooling channels of an injection mold cooling design should be placed as close to the surface of the mold as possible to reduce the amount of energy used to cool the mold while increasing the amount of energy used to cool the part. The goal of cooling is to solidify the part as soon as feasible. Using cooling effectively not only saves cycle time but also energy consumption.

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