Types
This type of hot runner system has many advantages that are not available with hot tip and sleeve type runner systems. If the gate opening and closing time can be controlled manually, the gate can be smooth and smooth, and the hot runner technology application technology field can be expanded.
Because the valve gate is closed by the mechanical action of the valve needle, it is not limited by the plastic cooling time at the gate, so the valve gate runner system can sometimes greatly reduce the production cycle of plastic parts. The size of the gate can also be made larger, which is very good for cutting-sensitive plastics. The valve gate method can process several grams of small parts and can also process large parts weighing several kilograms. All kinds of engineering plastics can use valve gate processing production parts. If there are multiple cavities of different sizes in a set of molds, such as the valve-type flow channel system, the control of the gate opening/closing time can be realized to realize the adjustment and control of the flow of each cavity. This is particularly important for molds with multiple molds that differ widely in shape and size. There are also molds for high productivity, having multiple layers of die faces, and only by using a valve hot runner system.
Action device
The mechanical action device of the valve needle can be controlled with hydraulic oil or compressed gas. With hydraulic oil valve needle switch action force is accurate. However, it is possible to contaminate plastic parts during the production process. Therefore, in the production of medical plastic products, it must be produced using a compressed gas control method to ensure that the products are clean. In addition, the use of the valve needle control device increases the height of the mold and the overall mold. In the mold design and injection molding machine selection should be considered. Valves for installing the valve control device must also be provided with cooling channels.
Precautions
As with the application requirements of hot-tip and cast-in-place hot runner systems, if the temperature control at the valve gate is not good, serious production difficulties can also result. For example, if the temperature at the gate is too high, the plastic may stick to the valve needle during mold opening. On the contrary, if the temperature at the gate is too low, the gate plastic is too cold, causing the valve needle to close and so on. Valve gate hot runner molds are more expensive than hot tip and nested hot runner molds. If the valve hot runner system and the valve needle control device itself are not well designed, there will be problems such as the formation of a dead angle behind the valve needle, or an overflow phenomenon on the sliding mating surface between the valve needle and other parts. In addition, if the valve needle is not well made, the closing movement operation is not properly controlled, and there are also serious consequences of damaging the gate. So although the valve hot runner system has many advantages that other two types of hot runner systems do not have, it also increases the complexity of the mold.
