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The Role Of Hot Runner In Plastic Mold Design
May 25, 2018

Core Tip: Hot runners are integral to injection molding. For plastics processors, choosing the right hot runner for the molding of the product, and understanding the proper use of the hot runner, benefits the hot runner.

        Hot runners are indispensable in injection molding production. For plastic processors, choosing the right hot runner for the molding of the product and understanding the proper use of the hot runner is the key to benefiting from the hot runner.

    The hot runner (HRS) is also called the hot water outlet, that is to turn the solidified water outlet into a molten one. The composition of the hot runner is relatively simple, including the manifold, hot nozzle, and thermostat. Among them, the manifold can be divided into shape, X shape, Y shape, T shape, mouth shape and other special shapes according to the shape of the manifold; hot nozzle can be divided into large nozzle, tip nozzle and needle valve nozzle according to the shape; temperature controller presses temperature control Methods can be divided into watch core type, card type and computer centralized control type.

In the injection molding process, the hot runner is used in conjunction with the mold and plays a very important role. For example, in the injection molding production of ultra-thin parts (such as cell phone battery covers), high-precision, high-quality products can be easily produced by using a hot runner; for a poorly-flowing injection molding material (such as LCP), a hot runner can be used. Can significantly improve the flow of raw materials to ensure the smooth progress of injection molding; For some large injection molded parts, such as car bumpers and door panels, TV rear shell, air conditioning shell, etc., through the use of hot runners, making very difficult injection molding become Relatively simplistic.


 In the multi-cavity mold injection molding, the lack of a hot runner cannot be formed at all. It can be said that the hot runner is the best technology to ensure the balance of the runners. Due to the shear force of plastic in the flow path, regardless of the reasonable geometrical balance of the mold, the weight of the molded product is also difficult to be consistent, especially for the multi-cavity mold, if the hot runner is not used, it is formed. The outside of the product will be lighter than the inside.


 For plastics processors, the use of hot runners is economical as long as there are a certain number of injection molding operations. This is because hot runners help companies eliminate nozzles in injection molding production. In most cases, the nozzle cannot be reused. Sometimes, the weight of the nozzle is almost the same as the weight of the product. If you use the traditional nozzle injection method, it means that the wasted material is as much as the raw material used in the product. Based on this calculation, after using hot runners, 30% to 50% of raw materials can be saved. In addition, the hot runner also helps to reduce mold wear and extend mold life. In general, the hot runner mold has a life that is twice that of the fine nozzle mold.


 Although the composition of the hot runner is relatively simple, each component of it plays an important role. In general, good hot runners require high structural design and materials. In terms of the first sharp hot runner, the selected heater and temperature sensing line were all imported from South Korea. The steel used was all imported from Japan. These are prerequisites for ensuring the quality of the hot runner.


 In addition, hot runner suppliers also need to help customers design and install a suitable hot runner system based on the customer's plastic products and the mold used. Xianrui has senior hot runner experts from South Korea. They can design reasonable solutions based on the customer's product conditions to ensure that the hot runner system can maximize its efficiency in injection molding processing. For example, in the design of the hot runner for Shanghai GM's door panel injection molding, the relevant components of the hot runner are selected based on full consideration of the materials used for the door panel. If the door panel is made of PP material, usually 3 hot runners can be used, that is, Y-shaped manifold and 3 hot nozzles. This solution can greatly reduce the manufacturing cost under the premise of guaranteeing the molding quality of the products; if the door panel uses fireproof ABS When materials are used, it is necessary to use 5 hot runners, that is, special diverter plates and 5 hot nozzles to ensure smooth molding of the products.


 When installing hot runners, note the following:

 ● Full inspection hot runner, including all dimensions, resistances, quantities;

 ● The size of the relevant part of the inspection mold and the hot runner;

 ● Before installing the panel, you must use a thermostat to carefully inspect the hot runner and confirm its normal operation before you can operate it.

 ● Before the production, the hot runner must be finally checked with a multimeter, otherwise it is not allowed to start;

 ● Before closing the mold, it must be shot in air. When air is ejected, cover the B-plate mold with cardboard, and then mold the mold.

 To help customers use hot runners properly, hot runner suppliers should train customers. The training content should include:

 ● The basic principle of the hot runner. The hot runner is electrically heated to keep the plastic in the runners in a molten state. Here, what needs to be especially emphasized to the customer is that the hot runner must have good insulation measures when working in the mold. Therefore, when making the manifold cavity, it cannot be replaced by square iron. This is very important in injection molding. of.

 ● Learn to properly install and remove hot runners. First of all, we must let customers know the hot runner sealer, which includes the sealing of the hot nozzle and the manifold, the sealing of the hot nozzle and the mold A, the sealing of the main nozzle and the panel, the guide of the valve needle and the valve needle guide Sealant and sealer for main jet and heat flow plate.

 ● Hot runner maintenance and service. The customer should be made aware that once the hot runner has a problem, it must be removed from the mold and repaired. This process takes at least 8 hours. For customers, the cost of their losses is about 10 times that of hot runner suppliers. Therefore, it is very important to maintain hot runners by full-time or part-time personnel.