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Application Of Hot Runner Technology For Injection Mold
Jun 25, 2018

The core message: hot runner technology, gradually entered the Chinese market in the 90's, but the current application of the overall proportion of less than 20%, and foreign hot runners have accounted for more than half of the injection mold. With the rapid development of domestic hot runners, the domestic market demand is very large.

The so-called hot runner mold refers to replacing the flow path of a conventional injection mold or a three-plate injection mold with a constant-temperature heated flow path, so that a novel structure that does not need to take out the flow path material at the time of molding is used.

So, where is the hot runner generally used? In this regard, this article will be discussed from several aspects.

one. Difference in mold structure

In the formation of super-sized plastic products, only the use of hot runners can make the plastic flow balance. For example, in the production of automotive interior linings, home appliances, and other components, it is necessary to carry more glue at the same time or chronologically. In this case, a hot runner is required to successfully complete this step. In addition, when the lateral injection is deviated from the center of the injection molding machine, the use of the hot runner glue can make the mold structure simple, and at the same time, the molding is easier, the molding speed is accelerated, the molding time is reduced, and no material head is produced. .

In general, when a three-plate method is used for injection, the heavy female template needs to slide on the guide post. Even if the new mold is difficult to bear the heavy burden caused by such sliding for a long time, the mold life is not long. In addition, in this mode, the amount of movement of the template that takes out the flow path material from the mold at each ejection is greater than the amount of movement of the template required to remove the molding from the mold.

Therefore, hot runners are usually used when:

1. Need to use a longer vertical flow path for the top side of the plastic;

2. To avoid problems caused by too long material heads;

3. Forming some large-scale or allow eccentric products into the plastic;

4. In the use of the three-plate die, it is necessary to move the master template to remove the material head. If the hot runner molding method is used, the mold opening movement can shorten the moving distance needed to remove the material head. Therefore, the three-plate mode requires a large molding machine to produce the cold runner, and the hot runner can be changed to a small molding machine.

5. For materials with characteristics such as high viscosity, low viscosity, or high molding temperature, the use of a hot runner system can solve problems such as difficult molding. For example, metal powders, ceramic powders, plastic magnets, plastic bearings, and injection molding of thermoplastic rubber.

two. Save plastic

1. With the use of a traditional cold runner, there will be cold heads, resulting in additional costs. For a simple example, if the cold heads account for 68% of the scrap rate (1kg of material can only produce 320g of product at the time of manufacture, and the remaining 680g of cold head), although the cold head is still recoverable, Due to factors such as the human factor and the mixture ratio of recycled materials, to maintain normal operation, some cold material heads must be accumulated, thus resulting in the retention of funds.

2. The hot runner can be applied in the field of high speed injection molding. High-speed injection molding not only improves the efficiency of molding, but also is necessary to control the wall thickness of products such as cups and containers.

3. Used in a stack mold. For products with a thin wall and a large number of products, such as a CD housing, only a 15% increase in clamping force can increase production by 80% at the same injection time.

three. Hot runner environmental protection and efficiency

Since the hot runner does not generate "garbage", there is no problem of dealing with "garbage". "Spam" means waste of resources, while hot runner systems are low-carbon products, and it will not produce harmful factors to the environment.

Due to the large variety of plastics and their often different shades of color, stockpiles accumulated during the injection molding process must be classified, dehumidified, dried and sealed. At the same time, the noise generated by smashing also has an adverse effect on the environment.

In summary, the hot runner is applied to the three-plate mold of an injection mold, which has the following advantages:

1. The material head is easy to remove and the stroke of the material head can be reduced;

2. At the time of injection, the plastic flow is relatively even, and the operating conditions of each injection point can also be separately controlled to make plastic injection easier;

3. Saves the cost and labor costs of plastic materials.