When discussing technology and applications of open and needle valve hot runners, we first need to understand differences between these two types of hot runners in key aspects. These differences not only affect their performance, but also determine their applicability in specific applications. Next, we will take a closer look at unique features of these two hot runner technologies.
[Definition Comparison]:
Open hot runner: At the end of injection cycle, product in mold cavity is opened by mold core holding pressure and cooling. At this time, mold opening force will pull small needle-like gate part at hot runner gate, thereby breaking it off. In some cases, a cold material handle is used to assist this process.
Needle valve hot runner: It relies on input air pressure or oil pressure to drive valve needle to move and realize hot runner's sealing function. This type of hot runner design is more flexible and can accurately control opening and closing of hot runner.
[Construction Comparison]: Open hot runners are simple in design and construction, have low processing requirements, are low in cost, and have relatively simple equipment protection. Needle valve hot runner is more complex, and its key components include valve needles, pneumatic or hydraulic drive devices, and solenoid valves, etc. Therefore, cost is relatively high and structure is more complex, but it has significant advantages in accurately controlling opening and closing of hot runner. At the same time, due to complex structure, needle valve hot runner is more prone to failure and requires more professional maintenance and repair.
[Feature Analysis]: Whether it is an open hot runner or a needle valve hot runner, there is a distinction between single point and multi-point. In an open hot runner, multi-point design means that all gates will be opened at the same time, and rubber may form a weld line or a clamp line at confluence. In contrast, needle valve hot runner is more flexible, and its multi-point gates do not have to be opened at the same time, but opening time of different points can be independently controlled as needed, thereby achieving precise adaptation to product structure.

 

[Component Differences]: Main components of open hot runner include a manifold (equipped with a coil heater), a hot nozzle (using a round sleeve heater or copper tube), an injection nozzle (also a round sleeve heater or copper tube), a temperature sensing line and a temperature control box. Needle valve hot runner involves a manifold (with a main nozzle), a hot nozzle, a cylinder, a valve needle valve sleeve, a gas valve, a junction box, screw screw accessories, also includes components such as a temperature sensing line and a temperature control box.

In production of parts with extremely strict requirements on appearance, needle valve hot runner shows significant advantages, especially in terms of weld line and gate treatment, and its performance exceeds that of open hot runner. In contrast, open gate is prone to whitening, high, and even wire drawing or leakage. In addition, needle valve hot runner also has a certain instability, which requires special attention.