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What are the two types of hot runner systems?

Date:2021-06-23View:606

The hot runner is heated to ensure that the plastics in the runner and gate adhere to the molten state.

The hot runner system generally consists of several parts such as a hot nozzle, a manifold, a temperature control box and accessories.

Thermal nozzles are generally divided into two types: open thermal nozzles and needle valve thermal nozzles. Since the hot nozzle method directly determines the selection of the hot runner system and the manufacture of the mold, the hot runner system is often divided into an open hot runner system and a needle valve hot runner system accordingly.

With an open hot nozzle, the pressure loss of the gate is relatively low; but the temperature of the nozzle tip is not easy to control; the temperature of the nozzle tip is too late to dissipate heat and there will be wire drawing.

To use an open hot nozzle, it is necessary to leave a cold material handle of 8-12mm on the nozzle head, and the nozzle head cover needs to be in full contact with the mold core (increase the heat dissipation of the nozzle head), which has higher requirements for the cooling environment near the nozzle head.

For the needle valve hot runner, the valve needle is driven to seal the glue by the air pressure and oil pressure inputted by the external electromagnetic signal after the injection cycle is over. The valve needle is driven completely by its own air pressure or oil pressure to complete the sealing and breaking of the glue. This is different from an open hot runner.

Needle-valve hot runners, depending on the way to drive the valve needles are different. There are two types of pneumatic drive and hydraulic drive. In addition, there are three types of single-point needle-valve hot runners without a splitter plate. The gate is usually They are all on the surface of the product, and they also have pneumatic or hydraulic drive equipment, namely cylinders (cylinders) and pistons. Therefore, the processing requirements for molds are relatively high, the requirements for plate thickness are different, and the structure is relatively complex, and they are usually used in large-scale injection molding. In terms of parts, there are also hot-to-cold and full-heat structures. For the composition of parts and components, different types of hot runners have different structures and gate methods, so the relevant composition is also different.

Because the needle valve hot runner is not restricted by the cooling time of the runner system, there is no cold runner, and the part can be ejected in time after it is formed and solidified. Many thin-walled parts have a relatively short molding cycle, which saves time and costs. Due to the needle valve type, the consumption of fine parts can be precisely controlled. The gate quality of the molded parts is good, the residual stress after demolding is low, and the deformation of the parts is small.