Control gate opening time of needle valve hot runner
1, needle valve hot runner, by controlling the opening time of the gate, to ensure the smooth filling of the cavity and the balance of melt flow, eliminate the weld mark.
Injection molding of large injection molded parts usually requires two or more hot gates to fill. For ordinary hot pouring systems, the gate is opened at the same time as the injection begins. Such a gluing method inevitably has a fusion defect, that is, when the two molten fronts converge, because the two molten strands can not be completely fused into one, and the fusion imprint is formed, and the reaction on the surface of the product is usually referred to as the fusion mark. Although it can be improved by increasing the melting temperature, increasing the holding pressure and adjusting the injection molding process parameters, the actual improvement effect is limited. The use of needle valve hot runner technology to build the pouring system can realize the program control of the opening and closing of each valve gate, and can control the first melt just past the second valve gate, the valve needle open, open the second gate, then the first gate can be opened or closed according to the need, and continue until all the gates are opened and the cavity is filled. The melt is completely fused to obtain products without weld marks.
2. The product obtained by this technology will not have residual gate marks, so it can be applied to the injection molding parts with high surface quality requirements.
Sometimes the valve gate is used because the mark of the valve gate on the workpiece is smooth, only equivalent to the mark left by an ejector pin, so it is much smaller than the mark at the end of the hidden gate and other types of hot runner.
3. More effective control of pressure holding and forming cycle.
The needle valve hot runner can use a larger diameter gate, which can speed up the flow of melt in the mold cavity, thus shortening the forming cycle of the part and better maintaining pressure.
4. Effectively reduce the internal stress of the product and improve the stability of the product.