Why Do Bubbles Form in Molded Plastic?

Bubbles in molded plastic can be caused by several factors. Here are some common reasons:

Trapped Air

Air can get trapped in the mold cavity if there isn’t proper venting. This trapped air forms bubbles within the plastic. Improve mold venting to allow trapped air to escape.

Moisture in Material

If the raw plastic material contains moisture, it can turn into steam during the molding process, creating bubbles. Ensure proper drying of the raw material to remove moisture.

Improper Injection Speed

High injection speeds can cause turbulence in the material flow, trapping air and forming bubbles. Adjust the injection speed and pressure to minimize turbulence and ensure complete filling.

Incorrect Pressure

Low injection pressure or insufficient holding pressure can lead to incomplete filling of the mold, resulting in air pockets.

Overheating

Excessive melt temperatures can cause the plastic to degrade, releasing gases that form bubbles.

Uneven Cooling

Inadequate or uneven cooling can cause the material to solidify improperly, leading to bubble formation. Optimize cooling times and temperatures to ensure even solidification.