Injection mold exhaust improper design will produce problems and analysis

In shot into the forming, when the mould completely shut down, cavity and runner fully occupied by air, so if he does not discharge the air, the melt injection materials will completely fill this part. So mold exhaust design must be reasonable design; Failed to completely discharge of air inside the cavity, difficult to get clear appearance and excellent quality products, seriously affect the quality of injection molding products. When design is not reasonable, can produce the following situation. A burning: when melt material filling speed is faster than the exhaust speed inside the cavity, the cavity in the air is compressed, immediately reach high temperatures ( This phenomenon is called break hot compression) , the portions of the molded products contact with high temperature air burning, black 2, fill bad: because of the breath within the cavity resistance to prevent the flow of the melt material, slow velocity, fill the bad phenomenon. Other dang in closed cavity in the amount of gas in the final residue in the cavity, if not millions of burning will fill the bad phenomenon. This kind of situation in hygroscopic material preparation is not completely dry the most likely to happen. Three, the material overflow: air in the cavity and the gas amount, inhibit the flow of the melt material, make the parting plane expansion, and expand the projection area of the same effect, caused by the parting surface buoyancy, and produce material overflow. This kind of phenomenon in thin meat products, especially easy to happen. In addition to the above points, the exhaust forming bad caused by incomplete, bubbles, silver wire, spray nozzle, appearance stains, etc. Cause analysis: first, the exhaust system section area is too small, in before repairing mold, cable head cap has no obvious flaws, both internal and external surface after expanding its thickness too thin, unable to meet the 'more than a expansion', the purpose of saving the cost of the mould. Must increase the thickness of plastic injection products, to meet the requirements of the head cap wall thickness. But in the mould at the same time not to cross section area of the exhaust system for timely correction. Improper 2 type, exhaust system design: as the injection head cap for semi-closed cylindrical shape, gate design in the center of the closed end a 臵, exhaust system design on the mold parting surface. And on the mold parting surface design only two symmetric exhaust gap, when the melt reached two 5 * 0 when parting surface. 02 symmetry discharge gap will be closed first, however, uniformly distributed around the parting surface cavity exhaust groove exhaust effect to be ideal, but difficult to mould processing, but not used. Three, the gate of the gating system is too small: because the gate size is according to the original without mold injection quality and design before, but after the mold modification, before feeding to pressure gate has been closed, to further the air discharge mode. Four, high injection speed: fast injection in point gate exit easy rebound after injection, impact core, easy to produce unstable jet flow, jet will be close to the exhaust system were piled at one end, the result in part of the air inside the cavity near the gate end cannot be ruled out. Measures: first, the exhaust system area is too small, the quality of the plastic cable head from 30 g/a increased to 40 / a, after the exhaust system to recalculate the size will exhaust system from 5 * 0. 02 * 2 * 0 to 10. 5 * 2 ( Deep wide * *) 。 Two type poorly designed and exhaust systems: due to mould layout arrangement and the machining difficulty, not uniform around the parting surface cavity along the cloth 臵 exhaust system, so still USES two symmetric exhaust system, but in the center of the moving mould a 臵 Φ 8. 0 hole, the center air compression chamber connected with the cavity and to reduce the pressure of the compression chamber. Three, the gate of the gating system is too small: appropriate increase the gate size or change the gate direct export to the export of the cone shape, can delay the gate closed time, in order to achieve better hold pressure, feeding and exhaust. Four, high injection speed: by adjusting the process parameters, appropriate to reduce the injection velocity, the elimination of jet would become extension flow or flow smoothly forward, in order to reduce exhaust system closed prematurely, and make the mold to discharge the air inside advantage. Hope I finish this information is helpful for you.





different causes of burns and injection mold parts are different solutions.


injection mould in production time due to some reasons, often produce burns. According to the machinery, mold or molding conditions caused by different reasons such as burns, are different solutions. 1.
mechanical reasons, for example, cylinder overheating due to abnormal condition, make resin pyrolysis, burns after injection into the products, or because of Jane internal nozzle and the screw thread, check valve and other parts of the resin caused by stagnation of decomposition after color change into products, with dark brown burn scars in the products. At this time, should be cleaning nozzle, screw and barrel. 2.
the cause of the mould, mainly because the venting is not good. This burns usually occurs at a fixed place, easily distinguished from the first case. At this time should be paid attention to and exhaust slot exhaust arm and other measures. 3.
in terms of forming conditions, when the back pressure is more than 300 mpa, can make the cylinder part overheating, cause burns. The screw rotation speed is high, also can cause overheating, generally within the scope of 40 ~ 90 r/min as well. Without a exhaust trough or exhaust slot is small, gas injection rate is too high will cause overheating burns.