Problems and solutions in injection molding process of PC/ABS alloy

PC/ABS is a thermoplastic plastic made of PC and ABS, which combines the excellent characteristics of the two materials.

Can be widely used in automotive trim, lampshade, handle, and other parts; Home and commercial appliances such as computers and peripherals, such as mobile phones, can be used instead of PCS for thin-walled, long-flow products.

Camera parts, instrument panel, FAN cover, hard hat housing, screw cap, radiator grille, computer and optical equipment housing, hair dryer, coffee pot, etc.

Injection grade ABS/PC alloy refers to a class of ABS/PC alloy with a high melt flow rate suitable for the actual injection molding process.

This kind of material has good melting fluidity, easy processing molding, heat flow resistance, and good rigidity.

Mainly used in automotive interior and exterior decoration materials, mobile phone shells, and laptop shells. The common problems and solutions in the injection molding process of PC/ABS alloy are as follows:

1. Pitting problem

The solution:

For poor dispersion, add dispersant or oil, increase injection molding temperature, and add back pressure. Keep an eye out for mold problems.

Try something else. Whether the baking material temperature time is sufficient. Mold temperature adjustment.

2. Warping and deformation problem

The warping deformation of injection molding parts is due to the unreasonable design of parts, improper gate position, and injection processing conditions are not reasonable.

So the internal stress, uneven or excessive shrinkage caused by the mold temperature is too high or the mold temperature is not uniform, causing the mucous membrane of the parts and demold difficult, or cooling is not uniform, the same will produce warping deformation.

The solution:

Processing technology: lengthen the injection molding cycle, reduce the injection temperature, adjust the injection pressure and injection speed properly, slow down the ejection speed, increase the ejection area, and maintain the balance of the ejection force; product design: increase the wall thickness, increase the reinforcement and the reinforcement at the rounded corner can reduce the warping deformation.

3. Flow mark problem

Flow marks are produced when the material is injected. The reason is that the material has poor fluidity.

Unlike silver marks, flow marks are not caused by moisture or material decomposition, and their appearance is also different.

The solution:

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

4. Shrinkage and indentation

Shrinkage cavity is caused by the insufficient high-speed filling of material in the mold cavity

The solution:

Appropriately raising the mold temperature and material temperature to improve the material fluidity, extend the injection pressure holding time, increase the injection pressure, and increase the injection speed to improve the mold filling, can also increase the size of the gate, heating the gate runner to reduce and eliminate the shrinkage of products.

5. Speckle problems

It is usually caused by “melt rupture” caused by the expansion of molten material into the mold cavity during the high-speed injection.

The solution:

Injection molding process: to increase the temperature of the material, increase the nozzle temperature, slow down the injection speed to reduce the appearance of markings;

Mold: increase mold temperature, add overflow groove, increase gate size, and modify gate shape.

6. Silver wire problem

Bad silver wire is the most common problem of PC/ABS materials, silver wire is also known as silver grain, spray, material flower, etc., is in the product surface along the flow direction of silver hair white filamentous-stripe phenomenon.

The main reason is the interference of gas, which is mainly divided into three components:

Air: air involved in the glue melting and injection stages;

The moisture contained in the material itself;

Pyrolysis gas: gas produced by high-temperature hydrolysis/thermal decomposition.

The solution:

Firstly, check whether the material is sufficiently dry. After confirming that the material is sufficiently dry, adjust the injection molding process to improve the silver wire defects. At the same time, bad injection silver wire is also related to mold exhaust.

7. Product “peeling” problem

The peeling problem of plastic products is closely related to the fluid rupture caused by high shear force. At low excessive shear stress or rate, small disturbances caused by various factors are suppressed by the melt.

However, at high shear stress or rate, the disturbance in the fluid is difficult to suppress and develops into an unstable flow. When a critical shear force is reached, a rupture of the fluid is caused.

The solution:

Material: the PC and ABS components are partially compatible, so it is necessary to add an appropriate compatibilizer in the modification injection molding process to improve its compatibility. Of course, the poor peeling caused by the mixture is the first step we need to eliminate.