1
Cold runner: refers to the part between the mold inlet and the product gate. Plastic maintains its flow state within the flow channel through injection pressure and its own heat. The flow channel is a part of the molding material, but it does not belong to the product. So when designing the mold, we need to consider both the filling effect and how to save materials by shortening or reducing the flow channel. Ideally, this is the case, but in practical applications, it is difficult to achieve the best of both worlds

II
Hot runner: As a commonly used component in injection mold systems, it ensures that the plastic in the runner and gate remains in a molten state through heating. Due to the presence of heating rods and heating rings near or in the center of the flow channel, the entire flow channel from the nozzle outlet of the injection molding machine to the gate is in a high-temperature state, keeping the plastic in the flow channel molten. After shutdown, it is generally not necessary to open the flow channel to remove the condensate. When restarting, only the flow channel needs to be heated to the desired temperature. Therefore, the hot runner process is sometimes referred to as a hot manifold system, or as runner free molding.

In short, the hot runner is the extension of the injection molding machine nozzle (barrel nozzle).