The location of the gate has a direct impact on the quality of the products, need to follow the following principles in determining the gate position. 1.The gate should be provided in the plastic section thickness, this gate, slower cooling, to melt through the gate into the mold cavity feeding, it is not easy to appear depression defects. 2.The gate location should melt flow shortest, flow change of minimum, minimal energy loss, general gate in the plastic parts center is better. 3.Out of the gate location should be conducive to the cavity gases. If entering the cavity melt prematurely closed exhaust system, can make the gas in the cavity is difficult to be discharged, and even affect the quality of the products, then, should reach the final position cavity open exhaust slot in the melt, and exhaust. 4.The gate location should be set up in front of the cavity wall or large core position, so that the high speed melt flow directly impact on cavity or core wall, thus changing the flow direction, flow rate reduction, smoothly filled cavity, which can eliminate the plastic part is obvious weld line, avoid melt rupture. 5.The gate number should not too much, if from several gate into a cavity, resulting in the possibility of weld mark will be greatly increased, if no special need, do not set the gate more than two. 6.The gate location should melt flow from the main to the cavity of the same or similar throughout the process, to reduce the generation of weld mark. 7.for the plastic parts with core or insert, especially the barrel shaped plastic parts with slender core, should avoid the partial feed, to prevent bending or insert shift type core. 8.The gate location should avoid melt fracture phenomenon, when the small gate facing the cavity width and thickness of large, high melt flow through the gate will be very high shear stress, resulting in injection and squirm of melt fracture phenomenon. But spray melt easily folded, to produce corrugated trace products. 9.of plastic melt in through the gate into the cavity, will produce the orientation, the position of gate should try to avoid the adverse effects of directional effect of polymer, and should use the directional role have beneficial effects on the plastic parts. 10.in determining the gate location and number of a mold, must be checked to ensure that the melt flow ratio, can fill the cavity, the flow ratio is determined by the ratio of flow passage length and total flow channel thickness. The allowable value with the nature of the melt temperature, injection pressure, vary. 11.for plate plastic deformation, warping, because it is easy, because it is in the direction of the shrinkage caused by inconsistent, if the use of multiple point gate, to much better effect. 12.for the frame type plastic parts, can be set according to the diagonal gate, can improve the plastic parts caused by shrinkage deformation. 13.for circular pieces of plastic, the gate should be placed in the tangential, can reduce the weld line, improve the welding position of strength, and good exhaust. 14.for the wall thickness of uniform pieces of plastic, the gate location should try to keep the process. Avoid vortex. 15.for the plastic shell, the gate layout center comprehensive feed, can reduce the weld line. 16.for the slender cylindrical, called shape, thin wall plastic parts, in order to prevent the lack of material, can be provided with a plurality of pour point, and set the process bars. The selection principle of gate location, the application may produce contradiction, then be flexible according to the actual situation. |