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3 Common Injection Molding Defects

A car part made through injection molding

Injection molding prototypes are both a science and art to create. For bulk production of unique parts, high levels of technical competence and attention to detail are necessary to avoid little mistakes costing organizations a lot of money.

In injection molding, there’s a lot of space for costly mistakes. Injection-molded product quality difficulties can range from tiny surface flaws to more substantial issues that compromise the product’s safety, performance, and function. They can be caused by issues with the molding process, the materials utilized, the tooling design, or a combination of the three.

Here are some common defects that occur with injection molding.

1. Sink Marks

When shrinkage happens in the interior regions of the finished product, sink marks appear as small dents or depressions in the thicker sections of the injection-molded prototype. The effect is similar to topographic sinkholes, except it is generated by contraction rather than erosion.

When the rate of cooling or the mechanism is inadequate for the plastic to properly cool and solidify while in the mold, sink marks are common. They can also be characterized by reduced cavity pressure or a high temperature at the entrance. Thick areas of the injection-molded item take more time to cool than thin sections, thus they’re more prone to be where sink marks appear.

2. Flow Lines

Flow lines are patterns, or streaks that appear on the prototype component as a result of the molten plastic’s physical path and cooling profile as it flows into the injection mold tooling cavity. They are typically dull in color. An entry section is where injection-molded plastic begins its trip through the part tooling. After that, it runs through the tool chamber and cools, finally solidifying.

The variable speed at which melted plastic travels as it changes its direction via the ridges and curves inside the mold tool causes flow line faults. They can also happen when plastic flows through portions with varied wall thicknesses or when the injection rate is too slow, allowing the plastic to harden at different rates.

3. Surface Delamination

A contaminating substance causes thin surface layers to develop on the part, which is known as surface delamination. These layers resemble coatings and are frequently scraped away.

Foreign materials that get into molten plastic detach from the end product since the pollutant and the plastic are unable to connect. Since they are unable to bond, it has an impact on the prototype’s appearance as well as its strength. The contamination behaves as a locally trapped defect within the material. Delamination can also be caused by an overreliance on mold-releasing agents.

A car part made through injection molding

These are some of the problems that do occur if injection molding is not done with utmost precision and care. For premium injection molding services in Grass Valley, contact Connekt LLC now. We offer other mechanical engineering services like 3D printing, rapid prototyping, FEA analysis, and more.

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