Troubleshooting the Line: Addressing and Preventing Injection Molding Defects

injection molding defects

Your team finally created a design that everyone approved. You chose a type of plastic and injection process that should have worked for the design. The prototype looked good.

However, production was paused because the parts had wavy lines across the surface. This is one of many possible injection molding defects.

Problems during the injection molding process waste time and money. You can avoid these issues if you know what to look for. Learn how to prevent common defects and how the right injection molding services can help.

Check the Injection Speed

If the injection speed is too fast or too slow, you’ll have injection molding defects. The plastic needs to cool uniformly to get the best results.

Increase the Injection Speed

Increasing the injection speed can help eliminate flow lines and weld lines. Flow lines are often wavy or ring-shaped. They’re a slightly different color than the area around them.

They don’t affect the structural integrity of the component, but the product won’t meet Class A standards.

Weld lines appear on the surface where the plastic meets itself after splitting around a hole or other feature. They reduce the strength and durability of the component.

Reduce the Injection Speed

You may need to reduce the injection speed if the component has burn marks.

Jetting is another problem that can result from an injection speed that is too fast. Jetting happens when the molten plastic doesn’t stick to the surface of the mold. The part has visible flow patterns on the surface and loses strength.

Adjust the Temperature

The temperature of the mold and the molten plastic affect how well the injection molding process works.

You may need to lower the mold temperature if you see sink marks. Sink marks look like dents or depressions in the part. A cooler temperature helps the plastic cure more evenly.

Increasing the mold temperature will often correct surface delamination. Delamination is a flaking surface layer that reduces the strength of the part.

Consider the Mold Design

A good mold design will help you avoid injection molding defects.

Short shots are one problem that can result from poor mold. A short shot is when the resin doesn’t fully occupy the mold cavity. Short shots are unusable because the component is incomplete.

Designing a mold with adequate venting for gas and gates that aren’t too narrow will help prevent short shots.

Look at the Condition of the Mold

Even a well-designed mold won’t last forever. Molds can become worn over time. They need proper maintenance and cleaning.

Using molds that are in good condition can help you avoid flash. Flash happens when molten plastic seeps out of the mold during shots. The plastic sticks out slightly from the edge of the finished component, requiring trimming.

Avoid Injection Molding Defects

Many factors can cause injection molding defects. A single type of defect can result from several causes, which makes troubleshooting more difficult.

The team at Nova Stevensville has over 100 years of combined experience in injection molding. We know how to identify and avoid injection molding defects.

Nova specializes in quick turnarounds with high-quality parts. We have gold standard recognition as a Tier-1 automotive supplier. Request a quote today to learn how we can help you meet your plastic design and manufacturing challenges.

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