Gates desing of Plastic Injection Molding

Gate design of Plastic Injection Molding includes gate section shape, gate section size and gate location.

The factors influence the gate section shape and size, in terms of products, including the product's shape, size, wall thickness, dimensional accuracy, surface quality and mechanical analysis, etc. The factors from raw material used in the plastic properties of the influence gate design are the plastic molding temperature, viscosity, contractility, and presence of fillers, etc. In addition, at the time of the gate design, gate should also be considered for processing, mold release and removal of the difficulty level of the gate.

As usual, the section size of the gate should be smaller rather than larger. When determining the gate size, make sure the smaller, and then try to test mould, if necessary we can revise according to the cavity filling conditions, especially to a multi-cavity mold, which can be made simultaneously to the cavity filling evenly through the amendment.

The small gate can increase molten plastic material flow rate and molten plastic material through the small gate will have much friction to raise the material temperatures. Which apparent viscosity decreased and advantageous to the filling. In addition, due to the small gate of fast curing, which does not produce excessive feeding and reduce the internal stress of products. At the same time it can reduce injection molding cycle and improve the gate removal.

Gate should not be too small for some products, such as thick-walled products, must be more than two times in the process of injection pressure to meet the requirements of products.  Too small gate will cause the gate place too early curing, the feeding difficulties will cause the product defects.

The Gate location should locate in the thickest area, so that the plastic flow from thick to thin-walled area and keep the process identical in all parts of the gate to the cavity,prevent jetting or worming during the filling process.

The gate location should  locate in the main stress direction, because the plastic flow direction on the highest tensile stress and compressive stress. When choosing gate location, we should consider the size requirements of the product. Because the plastic gate mold filling, the plastic flow direction and perpendicular to the flow direction of shrinkage varies is not the same. So we need consider  the direction of the deformation and shrinkage.

Shanghai Olimy-Professional in Fiberglass& Plastic Molding