The invention and application of hot runners has brought more opportunities for mold manufacturers; from general plastics such as polypropylene and polyethylene, to engineering plastics such as polycarbonate and glass fiber reinforced nylon, many different materials can pass. The hot runner system is processed. However, this technology and equipment often bring some troubles to mold manufacturers, and leakage is one of the problems.

Prerequisites for successful application of hot runner systems

One of the important differences between various hot runner systems is the way in which the melt is heated, which can be divided into internal and external heating. As the name implies, the internal heating system installs the heater directly in the melt tunnel and heats it from the inside; the external heating system heats the material externally, allowing the material to flow through the passage without obstacles. The external heating system solves the dead point problem in the melt channel and makes the shear curve in the melt channel more reasonable.

The hot runner system is an extension of the nozzle of the injection molding machine. The most efficient way to transfer the material to each injection port is to install a balanced manifold to ensure the length of the melt flow from the injection point to each membrane cavity. Same as the runner size. This mechanically balanced design ensures balanced filling of individual products while avoiding flash and short shots.

Different melt channel sizes directly affect the performance of the hot runner. Inappropriate melt channel size can cause plastic degradation, or unevenness in injection molding or incomplete filling, and slow color change. Moldmakers must consider factors such as pressure drop, residence time, temperature rise, shear rate, and color change frequency when determining the size of the melt.

After determining the type of system, you will then choose the appropriate gate type and its fill speed. There are a number of gate types to consider, including the allowed gate marks, gate locations, and the type of material being injected. Regardless of whether it is amorphous or crystalline plastic, different gate types have limitations on specific materials. Most hot runner systems can match different sizes of hot nozzles, each offering a specific fill speed. Too small a gate will limit plastic filling and may result in excessive shearing leading to material degradation.

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