Main sprue design for mould
The main sprue is the first part of the plastic melt entering the injection mold cavity. It introduces the plastic melt injected from the injection molding machine nozzle into the split runner or injection mold cavity, and its shape is conical, which facilitates the smooth flow of the melt. Before flowing. When the mold is opened, the main flow condensate can be pulled out smoothly. The size of the main flow channel directly affects the flow speed and filling time of the plastic melt. Since the mainstream road has to repeatedly contact and collide with the high temperature plastic and the injection molding machine nozzle, it is usually not directly Open on the fixed mold, but design it separately into the main guide set into the fixed template.
The main points of the design of the injection mold main sprue are as follows:
1. The main channel is designed to be conical in order to facilitate the pulling out of the casting system from the main flow channel and to consider the expansion of the plastic melt.
2. The big end of the main channel is rounded, and its radius is r=1~3mm to reduce the resistance of the flow velocity to the transition.
3. In the case of ensuring that the plastic parts are well formed, the length of the main flow path of the injection mold should be as short as possible, otherwise the aggregate of the main flow path will increase, and the pressure loss will be increased, so that the plastic melt cooling excessively affects the injection molding.
4. In order to make the molten plastic completely enter the main channel without overflow, the main channel should be closely connected with the nozzle of the injection machine, and the main channel abutment is designed as a hemispherical dimple. The main channel section is often designed as a detachable main channel bushing for the separate processing and heat treatment of high quality steel, so electric heating is used at the main channel to increase the material temperature.
Estimated ejection force formula From the book "Injection Mold
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