Injection molding process parameters and adjustments – injection molding, proces
First, a simple injection molding process can be expressed as follows:
Last cycle finished?? Closed mode?? Fill?? Packing?? Back to plastic?? Cool?? Mold?? Stripping?? Start next cycle
Pressure drop in the fill section of Paul, cavity pressure increased over time, after filling the cavity filled with the pressure to remain at a relatively static state, to supplement the contraction caused by the plastic as insufficient, while the pressure can prevent As the injection of colloid produced by the decrease of reflux, this is the packing stage, packing pressure after the expiry of the cavity decreased gradually, and over time can be reduced to zero in theory, but reality is not zero, so after stripping products within the internal memory, stress, and therefore some products and subject to reprocessing to remove residual stress. The so-called stress, is to Fu Gaozi chain or chains free movement of forces, that is, deformation, stress cracking, shrinkage and so on.
Two main parameters of injection molding process
1, injection of plastic material temperature, melt temperature on the melt flow properties play a major role, since no specific melting point of plastic, the so-called melting point is the temperature of a molten state section, the plastic molecular chains of the structure and composition of different therefore its fluidity is different, rigid molecular chain significantly influenced by temperature, such as PC , PPS So on, and flexible molecular chains as: PA, PP, PE and so on mobility by changing the temperature is not obvious, it should be adjusted according to different materials and reasonable injection temperatures.
2, the injection speed is within the melt in the barrel (also Screw The forward rate) speed (MM / S) injection rate to the product appearance, size, shrinkage, liquidity position distribution, usually the first slow?? Fast?? Slow, the first with a melt speed is more than over main channel, shunt, into the gate, in order to achieve a balance Injecting the purpose of filling mode and then quickly fill the mold cavity filling, then add a slower rate of contraction and lack of counter-current caused by the phenomenon of plastic material until the gate freeze This can be overcome burning, gas lines, shrink and other poor quality produce.
3, melt injection pressure is needed to overcome resistance, direct impact on product size, weight and deformation, different injection pressure required for different plastic products, for as PA, PP and other materials, will increase the pressure significantly improve its liquidity, the size of the injection pressure the density of a product, that is the appearance of gloss.
4, Mold Temperature, some plastic materials because of high crystallization temperature, crystallization is slow, requiring a higher mold temperature, and some as to control the size and deformation, or the need for stripping to a higher temperature or lower temperature, such as the general requirements of 60 degrees PC above, the PPS in order to achieve a better appearance and improved mobility, mold temperature above 160 degrees sometimes, and therefore die temperature on the improvement of product appearance, deformation, size, plastic mold has not underestimating the role.
3, injection shows the meaning of the professional parameters
1, injection volume Injection volume is Injection molding machine Screw in the injection, the injection mold by the melt volume.
Injection volume = screw advancing volume * * C
for the density of plastic materials
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