Injection molding machine injection molding process fluidity
1 Thermoplastic fluidity, generally can be analyzed from a series of indices such as molecular weight, melt index, Archimedes spiral flow length, apparent viscosity and flow ratio (flow length / plastic wall thickness). Low molecular weight, wide molecular weight distribution, poor molecular structure, high melt index, long snail flow length, low viscosity, and good flow ratio. For injection molding. According to the mold design requirements, the fluidity of common plastics can be roughly divided into three categories:
1 good fluidity PA, PE, PS, PP, CA, poly(4) methyl decene;
2 fluid medium polystyrene series resin (such as ABS, AS), PMMA, POM, polyphenylene ether;
3 poor flowability of PC, hard PVC, polyphenylene ether, polysulfone, polyarylsulfone, fluoroplastic.
2 The fluidity of various plastic injection molding machines is also changed by various molding factors. The main factors affecting are as follows:
1When the temperature of the material is high, the fluidity increases, but different plastics also have different, PS (especially high impact resistance and MFR), PP, PA, PMMA, modified polystyrene (such as ABS, AS) The fluidity of plastics such as PC and CA varies greatly with temperature. For PE and POM, the temperature increase and decrease has little effect on the fluidity. Therefore, the former should adjust the temperature to control the fluidity during molding.
2 When the injection pressure of the pressure injection molding machine increases, the molten material is subjected to large shearing action and the fluidity is also increased. Especially PE and POM are sensitive, so the injection pressure should be adjusted to control the fluidity during molding.
3 injection molding machine mold structure casting system form, size, layout, cooling system design, melt flow resistance (such as profile finish, channel section thickness, cavity shape, exhaust system) and other factors directly affect the melt in The actual fluidity in the cavity, the flowability is reduced when the melt is lowered in temperature and the fluidity resistance is increased. The mold should be designed according to the fluidity of the plastic used, and a reasonable structure should be selected. When molding, it can also control the material temperature, mold temperature and injection pressure, injection speed and other factors to properly adjust the filling to meet the molding needs.