The injection molds, which we call cold runner molds, are completed after each injection. After the mold is opened, there will be a cooling and solidification flow path that needs to be taken out manually or mechanically. The molds with hot runner systems (including hot nozzles, hot splitters, thermostats, hot runner coil heater,etc.) are called hot runner molds.
The advantages of hot runner molds compared to cold runner molds are:
1 When the wall thickness of the product is thin, ensure that the melt can reach the part far away from the gate (feeding port), greatly reducing the degree of product deformation, greatly improving the surface quality of the product and the consistency of the product.
2 The pressure loss in the flow channel is small, the melt fluidity is good, the density is easy to be uniform, and the defects such as deformation of the injection molded part, batch peak, dimensional instability and chromatic aberration are avoided.
3 All or most of the material removal (water nozzle), no need to manually cut the nozzle, no need to smash, improve the utilization of materials, save energy and improve production efficiency.
4 Eliminating the additional heat from the waste, the cooling cycle of the mold is only the cooling time of the plastic, shortening the processing cycle.
5 Hot runners automatically cut the gates to improve the appearance of the gate and improve the automation.
6 Precise control of the temperature of the melt plastic, eliminating the degradation of the material, making the dwell time more reasonable and reducing the internal stress of the product.
Because of these advantages of the hot runner system, in developed countries such as Europe, the United States, and Japan, more than 70% of injection molds use hot runner systems.
Classification of hot runners
Open type
The open structure is simple, the material has high limitation, the drawing and leakage are easy to occur, the surface quality is poor, and the application is less in the high-precision molds in foreign countries, and the same auxiliary mold can be mixed with the needle valve type of different manufacturers. Many companies can make it themselves.
Needle valve type
Needle valve type hot runner saves materials, the surface of plastic parts is beautiful, and the internal quality is tight and the strength is high.