Hollow Injection-Molded Parts: Challenges and How to Ensure Quality

Hollow plastic parts are among the most challenging to manufacture due to internal cavities and a lack of support. They are prone to warpage, uneven shrinkage, sink marks, surface waviness, and dimensional instability—issues that can affect assembly, sealing, and product lifespan.

With over 30 years of experience in precision mold design and injection molding, we have developed effective strategies to tackle these challenges.

Key Challenges

  • Warpage: Internal cavities lead to inward shrinkage during cooling, causing deformation and assembly difficulties.
  • Uneven wall thickness: Variations cause stress concentration, cracks, and sink marks.
  • Surface waving: Large flat areas may show subtle waves after molding.
  • Dimensional instability: Achieving tolerance at the first mold trial (T1) is difficult, increasing development time and cost.

Our Solutions

  • Add internal ribs: Strengthen structure, reduce shrinkage, and improve stability.
  • Optimize wall thickness: Ensure uniform shrinkage and reduce warpage.
  • Enhance support details: Use fillets, draft angles, support columns, and optimized snap-fits.
  • Improve mold cooling: Dense, well-planned cooling channels minimize deformation.
  • Select suitable materials: Glass-fiber reinforced or low-shrinkage plastics for large parts.

Conclusion

Hollow injection-molded parts can achieve high-quality, stable production with proper design, mold optimization, and process control. The key is professional engineering support—adapting the process to the product.

If you are developing hollow plastic components, we provide expert evaluation and structural optimization to ensure quality and reliability.

Need High Quality Injection Molded Parts?

If you have a great idea, we can help bring it to life. We’ve done this before and enjoy becoming partners throughout product creation. From advising you through the mold sourcing process to delivering your new product to customers, we want to work with you every step of the way.

A Never-Ending Pursuit to Get Better

Our strength is our flexibility and adaptability. We combine our experience with your ideas to bring out products that are one step into the future.

Quality Defect-Free Production

Our vision is to not only deliver products that exceed customer expectations but also to help them reduce costs by working with them in the mold design fields. 

On-Time Order Delivery 

We desire to ensure that customers receive the goods accurately and complete delivery in the shortest possible time.