Injection Molding Defects: Voids – Understanding the Cause and How to Fix Them

What Are Voids?

Voids are empty pockets or spaces that form inside your molded parts. While they might not always be visible from the outside, they can weaken the structure of your product, potentially causing failure down the road.

What Causes Voids?

Voids are usually the result of material shrinkage during cooling or improper venting in the mold. When the material doesn’t pack properly, it leaves behind these internal gaps, reducing the overall strength and integrity of the part.

Other factors that can cause voids include gating in the thin wall sections that flow into heavier sections or improper intersecting wall sections. These design choices can disrupt the material flow, increasing the risk of voids forming inside the part.

The Role of Material Selection in Avoiding Voids

Choosing the right material plays a vital role in reducing the risk of voids in injection molding. Different polymers have unique flow and shrinkage characteristics that can impact void formation. For instance, materials with lower shrinkage rates or those designed for high flowability are less prone to creating internal gaps. Working closely with your material supplier or a manufacturing partner like Aprios can help you select a resin that aligns with your design requirements while minimizing the risk of void-related defects. Balancing material properties with processing conditions ensures a more robust and reliable final product.

The Impact of Voids on Product Performance

Voids can have a significant impact on the performance and reliability of your molded parts. In applications where structural integrity is critical—such as medical devices or aerospace components—voids can compromise the part’s ability to withstand stress, vibration, or other environmental factors. Even in less demanding applications, voids may lead to cosmetic defects or customer dissatisfaction if the part fails unexpectedly. Identifying and addressing voids early in the manufacturing process is crucial to maintaining both product quality and your brand’s reputation.

Advanced Solutions for Tackling Voids

Modern manufacturing technologies offer advanced solutions to minimize void formation. For example, simulation software can predict where voids might occur during the design phase, enabling engineers to adjust the mold design or material selection proactively. In some cases, using alternative materials with better flow characteristics or lower shrinkage rates can further reduce the likelihood of voids. Combining these techniques with Aprios’ expertise ensures that your parts are optimized for both performance and manufacturability.

How to Prevent Voids

To prevent voids, it’s important to ensure the mold is well-vented and that the material is packed tightly into every cavity. Increasing the packing pressure and maintaining consistent cooling across the part are also key steps to avoiding this issue.

Additionally, maintaining uniform wall sections, properly sizing intersecting features, and gating in thick sections that flow to thin can help ensure better material flow and reduce the chances of voids forming.

If you’re experiencing voids in your parts and it’s affecting your product’s reliability, contact Aprios. We’ll help you troubleshoot and resolve the issue, so your parts are as strong as they need to be.