The Most Common Defects Found in Injection Molding

The Most Common Defects Found in Injection Molding

Injection molding is a great option for producing high volumes of perfectly identical parts. However, without an expert hand at the rudder, it’s easy to fall into a few common pitfalls and wind up with mistakes in your products. That’s why it’s important to hire a professional team to take care of your injection molding. Read on to learn the most common defects found in injection molding.

Flow Lines

When you notice off-color streaks or other patterns on your product, these are the result of “flow lines.” When molten plastic moves through a mold at different speeds, it can create flow lines. This usually indicates that the speed of injection and the pressure aren’t high enough.

You may also spot this defect when the resin moves through a mold with varying wall thicknesses. That’s why consistent wall thickness is essential to high-quality results.

Weld Lines

Weld lines, knit lines, and mold lines all refer to the same defect, and it’s perhaps the most common problem you’ll notice on your products. Luckily, it’s also easily solved after the fact. These occur at the parts of your mold where the halves meet.

When two plastic flows come together at these points in the mold geometry, they can form a small but visible line on the finished product. A simple filing tool can get rid of these mold lines quickly.

Sink Marks

The thicker sections of a part take longer to cool, which may cause depressions or dents in your product. These are called “sink marks,” and they usually indicate that the plastic needs a little more time in the mold to cool properly. You also may be able to address the problem by reducing the thickness of certain wall sections—this can facilitate even cooling.

When you work with Polymer Molding to get electrical connector caps or any other injection-molded part, you can count on us to follow the best practices and give you the best possible product.

Now that you know the most common defects found in injection molding, make sure you work with experts so you can mitigate the mistakes and enjoy high-quality products.

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1655 West 20th Street
Erie, PA 16502

Phone: 814.455.8085
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