🔧 Optimizing Injection Molded Part Design: Key Structural Features Explained
When it comes to injection molding, part design is everything. Even a small flaw in structural design can lead to warping, sink marks, or costly delays. Whether you’re prototyping or scaling into mass production, understanding the fundamental design elements of injection molded parts is critical for success.
🧩 1. Bosses – Supporting Fasteners the Right Way
Bosses are cylindrical protrusions designed to receive screws or inserts. They must be properly supported and dimensioned to avoid cosmetic and structural defects.
- Diameter: No more than 2× the wall thickness
- Add ribs or gussets around the base for reinforcement
- Avoid thick bosses that can cause sink marks
🦴 2. Ribs – Reinforce Without Bulk
Ribs add stiffness and strength to plastic parts without increasing wall thickness. Improper rib design can cause sink marks and flow hesitation.
- Thickness: 50–70% of nominal wall
- Height: ≤ 3× wall thickness
- Add draft angles to ease ejection
🛠 3. Gussets – Small but Strong
Gussets are triangular supports added near bosses or corners to increase localized rigidity. They are especially useful in load-bearing applications.
- Keep gussets short and angled
- Avoid overuse to reduce tooling complexity
📏 4. Uniform Wall Thickness – The Golden Rule
One of the most important principles in plastic part design is maintaining consistent wall thickness throughout the part.
- Reduces warpage
- Improves material flow
- Shortens cycle time
Avoid: Abrupt thickness changes and sharp internal corners
🌀 5. Radii and Fillets – Improve Flow and Strength
Sharp corners inside a plastic part cause stress concentration and poor flow. Adding internal radii improves both moldability and structural integrity.
- Use internal radius ≥ 0.5× wall thickness
- Add external fillets for a smooth flow path
📈 Benefits of Good Part Design
When you apply these core principles, you gain:
- Better mold flow and part filling
- Stronger structural integrity
- Shorter cycle times
- Fewer defects like sink marks and warpage
- Lower mold and production cost
🤝 Work with a Reliable Injection Molding Partner
At Xinjuexin Injection Molding, we support startups, product development firms, and OEMs worldwide in creating plastic parts that are designed for manufacturability. With decades of experience and in-house mold making and injection facilities, we ensure that your design translates into a reliable, high-quality product.
📩 Ready to Turn Your Plastic Design into Reality?
👉 Contact us today to get free DFM feedback or request a quote for your injection molded part.
