1.The gate is the last part of gating system, and section in the gating system the smallest part, the main role is as follows. Because the junction cross-section velocity is the fastest minimum, therefore, can make the melt to the fastest speed to enter and fill the cavity; when the cavity is filled with the molten material, with the decrease of temperature, melt the gate can be rapidly cooled and solidified, the mold cavity closed, can prevent backflow out without cooling cavity melt; the narrow gate gate section, so the plastic strength is very low, very easy to break, easy demolding; the gate length and cross section size can be adjusted in the graphite, solidification time to adjust melt the gate, and the fluidity of the melt during filling.
2.The gate size selection, the specific choice of gate size is determined according to experience, take a small value, then try modifying gradually die process. General requirements are: the ratio of area of the gate and runner sectional area is 0.03-0.09, usually circular or rectangular cross section. Gate section height h desirable products with minimum wall thickness of 1/3-2/3, or 0.5-2mm; in the velocity and wall thickness are under normal circumstances, the gate width b usually score channel narrow. On small products, its width is about 3-10 times the height; for large product or special fan gate, its width is greater than 10 times the height of the. The gate length of L should be as short as possible, it is favorable to reduce the melt flow of power and current velocity, generally take 0.7-2mm gate length. Sprue and cavity link should make R0.5 rounded or 0.5*45 chamfer, can prevent the separation of product and product damage the gate when the aggregate. In order to melt flow, should be a smooth transition links at the gate and runner, use a small circular smooth link. |