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How to Reduce Injection Moulding Cycle Time?

The time required for a plastic, such as nylon, POM, PC/ABS, to complete once injection moulding process is called the moulding cycle. It mainly includes injection time and cooling time.

The injection moulding cycle directly affects labor productivity and equipment utilization. Therefore, in injection moulding manufacturing, the relevant time in the moulding cycle should be shortened as much as possible under the premise of ensuring plastic parts quality. Injection time and cooling time are of the utmost importance throughout the moulding cycle and they have a decisive influence on the quality of injection moulded parts. The feeding time in the injection time is directly inversely proportional to the feeding rate, and the feeding time in injection moulding is generally about 3-5 seconds. The holding time in the injection time is the pressure time of the plastic in the cavity, which accounts for a large proportion in the whole injection time, generally about 20-120 seconds (the extra-thick parts can be as high as 5-10 minutes).
injection moulding
Before the frozen of the melt at the gate, the amount of holding time has an effect on the dimensional accuracy of plastic parts. The holding time also has the best value, which depends on the material temperature, the mould temperature and the size of the main runners and gates. If the size of the main runners and gates, and process conditions are normal, it usually takes the smallest pressure value as standard. The cooling time is mainly determined by the thickness of plastic parts, the material properties and crystallization properties, and the mould temperature. The end point of the cooling time should be based on the principle of ensuring that the injection moulded part does not cause changes during demoulding. The cooling time is generally between 30 and 120 seconds. The too long cooling time is not necessary, which not only reduces the production efficiency, but also make the demoulding of complicated parts difficult. Other times in the moulding cycle are related to whether the production process is continuous and automated, as well as the degree of continuity and automation.

Injection time: The injection time includes the feeding time and the holding time. Feeding time refers to the time that the screw advances rapidly, pushes the plasticized molten material into the mould, and the time required to fill the cavity is generally 3 to 5 seconds. For plastic parts with high melt viscosity and fast cooling rate, rapid injection should be used to reduce the feeding time of the melt. The holding time refers to the residence time after the screw advances and injects, that is, the cooling of the molten material into the cavity and the feeding time of the injected pressure. During this period of injection time, the proportion of the time is relatively large, generally about 20 to 120 s. The shape of the plastic part is simple, the outer shape is small, and the holding time is short. If the large plastic part and the wall thickness are large, the holding time is long.

Cooling timeThe cooling time refers to the cooling and solidification time of the plastic part after the melt is filled. The length of cooling time is related to the thickness of plastic parts, the material properties and the mould temperature. Generally, taking the non-deformation of plastic parts during demoulding as standard, and the shorter the time, the better. The cooling time of the plastic parts is generally in the range of 30 to 120 s.

Reducing the cycle time of the injection moulding helps to reduce plastic parts manufacturing costs. It allows the injection moulding machine to produce more products at the same time and with the same energy consumption. But what can we do to reduce the injection moulding cycle time?

1. Using high-speed injection moulding machines
The injection moulding machine has these steps of melting plastic, injection moulding, mould opening, mould closing and ejection. The function of the injection moulding machine itself is one of the main reasons that affect the injection moulding cycle time. The high-speed injection moulding machine has many advantages in terms of speed.
Make sure the mould structure is simple and easy to process, in other words, make the difficulty of mould design as low as possible. Most moulds can be designed in different ways, and there are many ways to demould. Simplified mould design can reduces cycle time in injection moulding.

2. Using good cooling system.
Use ice water to cool the mould. In addition to wasting time during injection moulding, the cooling also takes up a lot of injection moulding cycle time. Therefore, the use of low temperature cooling water and rapid passage of cooling water through the cooling system helps to reduce the cycle time in injection moulding.

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