We need to notice what when polypropylene molding
Writer： admin Source： 未知 Date：2018-04-20
Injection molding can application in many of plastic aspects, it can solve complex shape, precision size problems. Such as PP, because of its characteristics, it can effective solve old problems what can’t solved it before in molding process, but we need to notice when operation.
Polypropylene molding
1, Metal injection molding manufacturer introduced, as like PP crystallinity resin, the temperature of material barrel best choose more-high temperature and also rapid filling mould and quick cooling. In actual, in order to reduce burr and marks, the temperature of material barrel is usually slight low when molding. Normally, the temperature in the front of material barrel choose around 180℃， the rear temperature is around 220℃。
2，The screw retreat amount and injection pressure are preferably stopped one second before the injection timer setting time， the best is can be filling mould when the pressure of injection is low, but for actual parts, if the pressure of injection is too low, it will easy to happen marks and rack of material. The pressure of injection is around 30MPa. The high pressure injection, it is easy to burr, thus, it need to notice the injection pressure. The injection pressure divided into two step that is the best, it should cut the second step pressure when resin filling 95%, the pressure of second step is around 80% as the first step. Such as, the injection pressure of first step is 10MPa, the second pressure is 8MPa.
3, The speed of injection PP is better fastest, but the injection speed is too fast, the part is easy to burr and flash. The injection speed means the speed of screw forward.
4, Metal injection molding manufacturer introduced that cooling time part need cooling to a certain hardness, it can put out from mould. In order to reduce cooling time, we can add the mould heat exchange. For actual components, the time of screw back is long than cooling time.
