There are many expensive mistakes when it comes to injection molding of Pet Bottle Mould. The quality of injection molded products ranges from minor surface defects to more serious problems affecting product safety, performance and functionality. They may be caused by problems associated with molding processes, material usage, tool design, or a combination of all three.

But like any quality issue, knowing how molding defects are produced is half the battle (related: how experienced importers limit product defects in three stages [e-books). As an importer or manufacturer of injection molded products, some knowledge of common injection molding defects and how to avoid them can help you reduce the cost of non-saleable goods and product returns.

Let's take a look at the most common quality defects associated with injection molding, what is causing these defects, and what you can do to prevent them.
Molding defects are usually caused by process problems

Some molding defects can be difficult to solve or costly. Other problems can be avoided by adjusting the molding process without the need to redesign the mold or replace other production equipment. Generally, these defects can be relatively easily avoided by adjusting the flow rate, temperature or pressure of the mold.
1. Deformation streamline

The streamline appears as a wave pattern, usually with a slightly different color than the surrounding area, usually located in a narrower portion of the molded part. They may also appear as an endless belt on the surface of the product near the entrance point of the mold or the "gate" through which the molten material flows. Stream markers usually do not affect the integrity of the component. But they may be ugly, and if found in some consumer products, such as high-end sunglasses, it may be unacceptable.
Streamline reasons and remedies

Streamlines are typically the result of changes in cooling rate as the material flows in different directions in the mold. Differences in wall thickness can also cause the material to cool at different rates, leaving a flow line. Injection molding defects, such as molten plastic, cool very quickly during the injection process, and when the injection speed is too slow, the flow marks are noticeable. The plastic becomes partially solid and sticky while filling the mold, resulting in the appearance of a wave pattern.

The following are some common remedies for streamlines in injection molded products:

Increase injection speed, pressure and material temperature to ensure that the material fills the mold before cooling
Corners that increase around the wall thickness of the mold to help keep the flow rate consistent and prevent flow lines
Reposition the mold gate to create a greater distance between the gate and the mold coolant to help prevent premature cooling of the material during flow
Increase nozzle diameter to increase flow rate and prevent early cooling

2. Burn marks

Burning marks typically exhibit a black or rust-colored discoloration on the edges or surfaces of molded plastic parts. Injection defect burn marks usually do not affect the integrity of the part unless the plastic is burned to the extent of degradation.
Causes and prevention of burn marks

A common cause of burn marks in injection molded parts is the overheating of air or resin itself in the cavity during injection. Excessive jet velocities or heating of the material often cause overheating and burns. Consider the following precautions to avoid burn marks on molded parts:

Reduce melt and Pet Preform Mould temperatures to prevent overheating
Reduce injection speed to limit the risk of trapped air in the mold
Enlarge the air vents and gates to allow trapped air to exit the mold
Reduce mold cycle time so that any trapped air and resin will not overheat