How To Select A Suitable Hot Runner System

Selecting a suitable hot runner system requires a comprehensive consideration of multiple factors. The following are some key points for selection:
Production batch: For large-scale production with an annual output exceeding 500,000 pieces, the advantages of the hot runner system, such as no runner condensate and improved production efficiency, can significantly reduce long-term costs and offer better cost performance. For small-batch production with an annual output of less than 50,000 pieces, cold runner molds are more suitable due to their simple structure and low cost. For medium-batch production with an annual output of 50,000 to 500,000 pieces, the mixed flow channel can balance efficiency and cost.
Material properties: When processing glass-reinforced plastics, such as glass-reinforced nylon materials, etc., gate inserts with good wear resistance should be selected. When processing plastics that are prone to thermal decomposition, such as PVC, a hot runner system with unobstructed gates and no dead corners for flow should be selected. When processing plastics with poor fluidity, such as PC, it is advisable to consider using larger nozzle series and larger runner cross-sectional dimensions in the hot runner plate, etc.
Product structure: Thin-walled parts with a thickness of less than 1mm have high requirements for filling pressure. The hot runner can ensure that the melt fills the cavity at a stable pressure and temperature. For multi-cavity molds with more than 32 cavities, the use of hot runners can better balance the fluidity of each cavity and ensure product consistency. For products with metal inserts, a mixed flow channel can be adopted, and local heating can be used to prevent stress concentration.
Appearance requirements: For products with high gloss and mirror-like effects, such as optical lenses and mobile phone casings, the hot runner needle valve gate can achieve seamless injection molding. For products with ordinary appearance requirements, the cold runner latent gate has a low cost. For products with textured surfaces, a mixed runner and hot runner area can be polished to #8000 mesh.
Injection molding pressure loss: The injection molding pressure loss in the hot runner system cannot be ignored. For processing plastics with poor fluidity, such as PC and POM, when the melt flow distance in the hot runner system is large or the weight of the workpiece is heavy, CAE software should be used for runner analysis and calculation to ensure the smooth injection molding.
Types of hot runner systems: Hot runner systems mainly include three types: hot tip type, sprue type and valve needle type. Hot-tipped nozzles are suitable for a variety of plastics and have a relatively simple structure. The valve needle gate can precisely control the melt flow and is suitable for applications with high requirements for gate marks and multi-chamber balance.
Heating method: The internal heating system directly installs the heater in the melting channel to heat the raw materials from the inside. The external heating system heats the raw materials externally, allowing them to flow through the channel without hindrance. The external heating system resolves the dead point issue in the melt channel and makes the shear curve within the melt channel more reasonable.
Supplier selection: It is necessary to choose a hot runner supplier with a rich product range and reliable quality. The hot runner components should have good performance and durability, and should have obtained ISO quality standard certification from international organizations, etc. Meanwhile, the supplier should have good technical support and after-sales service in the region where the mold user is located, and be able to promptly solve the problems that occur during the use of the hot runner system.