Haochen Hot Runner tells you that hot runner molds can be divided into open hot runner molds and needle valve hot runner molds.

Due to the fact that the open hot runner breaks through the condensation gate when injecting glue with the screw of the injection machine forward, it can only be injected into the mold. Conversely, when the screw in the injection machine retreats, it can only be condensed with the gate to close the glue outlet. So usually, the choice of gate size is quite important. Otherwise, due to the temperature of the gate area, either the hot nozzle cannot eject glue due to condensation blockage, or there is wire drawing and salivation at the gate of the hot nozzle. If the gate cannot condense at the same time when the screw retracts, it will form a back suction force on the mold cavity, which is not conducive to maintaining pressure in the cavity. Commonly used are a bit gate hot runner, a straight gate hot runner, and a sub gate hot runner with sub runners. Due to the simple structure of the open hot runner, simple mold processing, and low maintenance costs, as well as the low requirements for the appearance of injection products or the consideration of procurement costs, there are still many users who use this type of hot runner without or with very few nozzle material heads after use. Commonly used are a bit gate hot runner, a straight gate hot runner, and a sub gate hot runner with sub runners.

The needle valve type hot runner, when the gate of the hot nozzle moves forward with the screw of the injection machine during the injection of the first mock examination with multiple hot nozzles, can adjust the valve needle to open the gate and inject glue in order through the gas (liquid) pressure, which can adjust the water inclusion line, shrinkage, warpage and other problems of the product appearance. On the contrary, when the screw in the injection machine retreats, the valve needle can be adjusted in order of gas (liquid) pressure to seal the gate without injecting glue. This sequential control can also compensate for the uneven filling of the mold cavity when multiple hot nozzles are simultaneously spraying glue. In addition, the needle valve hot runner gate is made slightly larger to reduce the shear heat of the glue outlet. By instantly opening and closing the glue outlet, the mold cavity is filled quickly, with good pressure retention, and no wire drawing or salivation. Only by using needle valve hot runners can it be used for injection molding of laminated cavity molds and multi cavity family products. The needle valve hot runner structure is relatively complex, and it has relatively high machining accuracy and maintenance for molds. Although users consider procurement costs, it has many advantages and is also adopted by most users.

The needle valve hot runner is divided into three types: cylinder type needle valve hot runner, cylinder type needle valve hot runner, and spring type needle valve hot runner. The cylinder type needle valve hot runner uses air pressure to push the valve needle to open or close the gate to complete the glue injection mode. This method is convenient to use because there is ready-made compressed air in the injection workshop, and the connecting pipe is directly input into the hot runner cylinder. However, the air pressure is limited, and it is also used by a large number of users. The oil cylinder needle valve hot runner uses hydraulic pressure to push the valve needle to open or close the gate to complete the injection mode, and requires an oil pressure pipe to input into the hot runner oil cylinder. This method is commonly used for injection molding of plastic parts with large surface area and wall thickness due to high hydraulic pressure. The hot runner of the spring type needle valve adopts a locking spring compression method to push the valve needle open or close the gate to complete the glue injection mode. The pressure adjustment is relatively small, but it is convenient to use and has fewer users.