Plastic mold in the mold design we need to pay attention to what matters? Plastic mold

First, injection mold measurement and plasticization

In the molding process, the control of injection volume (metering) and the uniform melting of the plastic (plasticization) are performed by the extruder plasticizing mechanism.

1, heating cylinder temperature

Although plastic melts, about 60 - 85% is due to the heat generated by the rotation of the screw, the molten state of the plastic is still affected by the temperature of the barrel, especially near the front of the nozzle - It is easy to happen when the material is dripped and the workpiece is pulled out when high

2, screw speed

(1) The melting of plastic, generally due to the heat generated by the rotation of the screw, so the screw speed is too fast, the following effects:

① plastic thermal decomposition;

② glass fiber (plus fiber plastic) to reduce;

③ screw or heating tube wear faster.

(2) speed setting, the size of its peripheral speed to measure:

Circle speed = n (speed) * d (diameter) * π (pi). In general, plastic with good low-temperature thermal stability can be set at about 1 m / s around the screw. The plastic with poor thermal stability should be as low as about 0.1.

(3) In practical applications, we can try to lower the screw speed, so that the rotary feed can be done before the mold is opened.

3, back pressure

(1) When the screw rotating feed, advancing to the front of the screw melt pressure accumulation is called the back pressure injection molding, the injection pressure can be adjusted by adjusting the discharge pressure cylinder, the back pressure can have the following Effect:

① melt more uniform melting;

② toner and filler more uniform dispersion;

③ the gas exit from the discharge port;

④ feeding accurate measurement;

(2) The level of back pressure is determined by the viscosity of the plastic and its thermal stability. Too high back pressure prolongs the feeding time, and also tends to overheat the plastic due to the increased shearing force. Generally 5-15kg / cm2 is appropriate.