Common problems and countermeasures of PC/ABS materials

1, the silver wire problem

Silver wire defect is the most common problem of PC/ABS material. Silver wire, also known as silver grain, water flower, flower flower, etc., is a silvery white filamentous stripe phenomenon appearing along the flow direction on the surface of the product, gas interference, among which The gas produced is mainly divided into three components: (1) air: molten rubber and air entrapped in the injection stage; (2) moisture: moisture contained in the material itself; (3) cracked gas: generated by high temperature hydrolysis/thermal decomposition gas.

Solution:

First check whether the material is dry enough, and after confirming that the material is dry enough, adjust the injection molding process to improve the silver wire defect. At the same time, poor injection molding silver wire is also related to mold exhaust.

2, the problem of flow marks

Flow marks are produced when the material is injected. The reason is that the material has poor fluidity. The flow marks are different from the silver lines. It is not caused by moisture or material decomposition, and the appearance is different.

Solution:

It can be avoided by increasing the temperature of the material to improve the fluidity, and appropriately increasing the mold problem to increase the fluidity of the material in the mold and reduce the injection speed can also be solved.

3, shrinkage holes and dent problems

The shrinkage cavity is caused by insufficient filling of the material in the cavity.

Solution:

Properly increase mold temperature and material temperature to improve material flow, prolong injection pressure retention time, increase injection pressure, increase injection speed to improve mold filling, increase gate size, and heat gate flow path And eliminating shrinkage holes in the product;

4, warpage deformation problem

The warping deformation of the injection molded parts is due to the unreasonable design of the parts, improper gate position and unreasonable injection molding conditions, resulting in internal internal stress, uneven shrinkage or excessive, excessive mold temperature or uneven mold temperature. It causes difficulty in demolding the film of the workpiece, or uneven cooling, and warp deformation also occurs;

Solution:

(1) Processing technology: lengthen the injection molding cycle, reduce the injection temperature, adjust the injection pressure and injection speed, and slow down the ejection speed, increase the ejection area, and maintain the balance of the ejection force;

(2) Product design: increase the wall thickness, add reinforcement and fillet reinforcement to reduce warpage.

5, the problem of marking

Usually due to the "melt fracture" caused by the expansion of the melt into the cavity during high-speed injection;

Solution:

(1) Forming process: reduce the occurrence of speckle by increasing the temperature of the material, increasing the nozzle temperature, slowing down the injection speed, etc.;

(2) Mold: Improve the mold temperature, add overflow tank, increase gate size, and modify gate shape.

6, pitting problem

Solution:

(1) Poor dispersion, adding dispersant or oil, raising temperature, adding back pressure.

(2) Pay attention to the mold problem. Try it with something else.

(3) Whether the temperature of the baking material is sufficient.

(4) Mold temperature adjustment.

7, dent problem

The dent is caused by improper temperature of the material and improper design of the product. When the temperature of the material is too low, not only shrinkage holes but also dent problems will occur. The temperature of the material is too high and the mold temperature is too high, which will cause the melt to cool. The time is excessively contracted, resulting in dents.

Solution:

Improve injection speed and measures with appropriate processing problems.

8, the product "skinning" problem

The peeling problem of plastic products is closely related to the cracking of fluid caused by high shear force. Under low shear stress or rate, small disturbance caused by various factors is suppressed by melt; while in high shearing At stress or rate, disturbances in the fluid are difficult to suppress and develop into unstable flow; when a critical shear force is reached, the fluid will be broken.

Solution:

(1) Materials: The PC and ABS components are partially compatible, so it is necessary to add a suitable compatibilizer during the modification to improve the compatibility. Of course, because of the poor skinning caused by the mixing, we need the first step to eliminate;

(2) Mold: The principle of mold design is to follow the direction of cutting as much as possible. In general, products with dense dermatoglyphics are more prone to skinning (diffuse shearing of the melt in the cavity and the inner wall of the cavity during high-speed filling); at the same time, the gate size is too small. Will cause excessive shearing when the melt passes through the gate, which in turn causes the product surface to peel;

(3) Injection molding process: The main direction is to avoid excessive shearing. When the product is difficult to fill, it can be improved by high-speed and high-pressure method. Therefore, in the actual injection molding process, the injection temperature/die temperature and the fluidity of the material can be considered to reduce the flow resistance during the actual filling process, thereby Avoid excessive shear caused by high speed and high pressure.