Common problems and Solutions in PC/ABS Producing (2)

Common problems and Solutions

4 Warping deformation problem

Warpage of injection molded parts is due to unreasonable design of workpiece improper location of gate and injection molding conditions, resulting in internal stress, contraction uneven or excessive. mold temperature is too high or mold temperature unevenness, causing the workpiece mucous membrane and demoulding difficulties, or cooling unevenness, will also produce warping deformation;

Solution:

(1) in the processing method aspect: lengthening injection molding cycle, reduce injection temperature, appropriatly adjustment injection pressure and injection speed, while slowing the ejection speed, increase the top out area, maintain the top output balance;

(2) in the product design aspect: increases the wall thickness, adds rib reinforcement or stiffeners in the fillet place may reduce the warping distortion;

 

 

5 Stripe problems

Usually due to the high speed injection, melt expanded into the cavity and caused "melt rupture";

 

Solution:

(1) in molding process: Improve the material temperature, improve the nozzle temperature, slow down the injection speed, etc. to reduce the appearance of stripe markings;

(2) in mold aspect: Improve mold temperature, add overflow trough, increase gate size, modify gate shape.

 

 

6 Pitting problem

Solution:

(1) add dispersant or oil, raise temperature, add back pressure to improve its poor dispersion.

(2) Pay attention to if it is the mold problem. Try some other material.

(3) Whether the baking temperature time is enough.

(4) Adjust Mold temperature.

 

 

7 "Peeling" problem

There is a great connection between the product peeling problem and the rupture of fluids caused by high shear force. In the low shear stress or rate, the small disturbance caused by various factors is inhibited by the melt; but in the high shear stress or rate, the disturbances in the fluid are difficult to suppress and develop into unsteady flow. When a critical shear force is reached, the fluid rupture is caused.

 

Solution:

(1) Material aspect: the PC and ABS two components are partial compatibility, therefore must add the appropriate compatibility agent in the modification process to enhance its compatibility. Of course, the peeling problem caused by mixture is the first step we need to exclude;

(2) Mold aspect: the principle of mold design should be followed to minimize the direction of shearing. In general, dense striae surface products are more prone to the emergence of peeling problem (caused by the friction shear of the melt in the cvity with the cavity internal wall while in the high-speed filling); At the same time, the gate size is designed too small, will result in excessive shearing when the melt through the gate , and then lead to the surface of the product peeling;

(3) Injection molding process aspect: The main direction is to avoid excessive shearing. High speed and high pressure can make the product filling easier. Therefore in the actual injection process, may also consider raising the injection temperature/mold temperature, as well as enhancing the material fluidity to reduce the flow resistance in the actual filling process, thus to avoid excessive shear caused by high pressure.

 

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