Hot runners are already indispensable in injection molding production. For plastic processors, choosing a hot runner suitable for product molding and mastering correct use of hot runner is key to benefit from hot runner.
Hot runner (HRS) is also called hot water outlet, which turns solidified nozzle into a molten nozzle. Its composition is relatively simple, mainly including a manifold, a hot nozzle, a thermostat, etc. Among them, manifold can be divided into I-shaped, X-shaped, Y-shaped, T-shaped, mouth-shaped and other special shapes according to shape; hot nozzle can be divided into large nozzle, pointed nozzle, and needle valve nozzle according to shape; thermostats can be divided into watch core type, plug-in type and computer centralized control type according to temperature control method.
In injection molding process, hot runner is used in conjunction with mold and plays a very important role. For example, in injection molding production of ultra-thin parts (such as cell phone battery covers), high-precision and high-quality products can be easily produced by using hot runners; for injection molding materials with poor fluidity (such as LCP), use of hot runners can significantly improve fluidity of raw materials and ensure smooth progress of injection molding production; for some large injection molded parts, such as automobile bumpers and door panels, TV rear shells, air-conditioning shells, etc., use of hot runners makes very difficult injection molding relatively simple.

 

In multi-cavity mold injection molding, lack of a hot runner cannot be molded at all. It can be said that hot runner is the best technology to ensure balance of runner. Due to shearing force of plastic in runner, no matter how reasonable geometric balance of mold is, weight of molded product is difficult to be consistent, especially for multi-cavity mold, if hot runner is not used, outer side of molded product will be lighter than inner side. .
For plastic processors, as long as there is a certain batch of injection molding production, use of hot runners is quite economical. This is because hot runners help companies eliminate nozzles in injection molding production. In most cases, nozzle cannot be reused. Sometimes, weight of nozzle is almost same as weight of product. If traditional nozzle injection method is used, it means that as much raw material is wasted as raw material used in product. Based on this calculation, after using hot runner, 30% to 50% of raw materials can be saved.
In addition, hot runner also helps reduce mold wear and extend life of mold. Under normal circumstances, service life of hot runner mold is twice that of nozzle mold.
Although composition of hot runner is relatively simple, each of its components plays an important role. Generally, high-quality hot runners have high requirements for structural design and materials.
In addition, hot runner suppliers also need to help customers design and install suitable hot runner systems based on their plastic products and mold conditions.
For example, in the design of hot runner for injection molding of door panels of Shanghai General Motors, relevant components of hot runner are selected on the basis of full consideration of materials used in door panels.
If door panel is made of PP material, 3 hot runners are usually used, that is, a Y-shaped manifold and 3 hot nozzles are used. This solution greatly reduces manufacturing cost under premise of ensuring quality of product molding; if door panel uses fire-resistant ABS, it must use a 5-point hot runner, that is, a special splitter plate and 5 hot nozzles to ensure smooth forming of product.
When installing hot runner, you need to pay attention to following points:

 

● Fully inspect hot runner, including all dimensions, resistances, and quantities;
● Fully inspect dimensions of mold and related parts of hot runner;
● Before installing panel, you must carefully check hot runner with a thermostat and confirm that it is working properly before you can operate it;
● Before production, a multimeter must be used to conduct a final inspection on hot runner, otherwise it is not allowed to start;
● Before clamping mold, it must be shot empty. During blank shot, cover B-board mold with cardboard, then close mold and test mold again.
In order to help customers use hot runner correctly, hot runner supplier should train customer. Training content should include:
● Basic principle of hot runner. Hot runner is electrically heated to keep plastic in runner in a molten state. Here, it is necessary to emphasize to customers that when hot runner is working in mold, it needs to have good heat preservation measures. For this reason, square iron cannot be substituted when making manifold cavity, which is very important in injection molding.
● Learn to install and remove hot runner correctly. Customer must first understand sealing position of hot runner, which includes sealing of hot nozzle and manifold, sealing of hot nozzle and mold A plate, sealing of main nozzle and panel, sealing of valve needle and valve guide sleeve, sealing of main nozzle and hot runner plate.
● Maintenance of hot runner. To let customers realize that once hot runner has a problem, it must be removed from mold for repair. This process takes at least 8 hours. For customer, cost of loss is about 10 times that of hot runner supplier. Therefore, it is very important to maintain hot runner by dedicated full-time or part-time personnel.