TUOWEI PRECISION follows a refined overmolding workflow that ensures every part meets the highest standards of precision, durability, and aesthetics. Our process is a combination of technical expertise, material science, and advanced tooling.
Substrate Design & Engineering
We begin by designing and engineering the core substrate with exacting specifications. Our engineering team considers dimensional accuracy, bonding requirements, and mechanical performance to ensure the substrate is an ideal foundation for the overmold layer.
Precision Substrate Molding
Using advanced injection molding machines, we produce the rigid substrate often from materials such as ABS, PC, or metal inserts. Every piece is checked against tolerance benchmarks to guarantee a perfect fit for the overmolding stage.
Surface Preparation & Treatment
Before applying the overmold, we prepare the substrate’s surface to maximize adhesion. This may involve cleaning, texturing, or plasma treatment, ensuring the secondary material bonds securely and resists peeling or cracking over time.
Secondary Material Injection
The prepared substrate is placed into a specialized mold where a softer material such as TPE, TPU, or silicone is precisely injected over or around it. Our temperature and pressure controls ensure consistent bonding, dimensional stability, and defect-free finishes.
Quality Inspection & Finishing
Once molded, each part undergoes a rigorous inspection process. We check for bonding strength, dimensional accuracy, and visual quality. Any necessary finishing, such as trimming or polishing, is completed before parts are packaged for delivery.
What Challenges Occur in Overmolding And How to Overcome Them?
While overmolding offers significant advantages, it comes with unique manufacturing challenges. Addressing these issues early can reduce waste, improve cycle times, and ensure consistent product quality.
Material Compatibility
Challenge: Not all materials bond well. If the substrate and overmold material are incompatible, the layers may peel, crack, or fail under stress.
Solution: Select materials with proven adhesion properties. For example, pairing polycarbonate (PC) substrates with TPE overmolds has a high success rate. Conduct adhesion tests before mass production investing in compatibility testing can save up to 20% in rework costs.
Dimensional Accuracy and Shrinkage
Challenge: Differences in thermal expansion between materials can cause warping or dimensional inconsistencies.
Solution: Adjust mold design to compensate for material shrinkage rates. Using precise temperature control during the second molding stage can reduce deformation by up to 30%.
Flash and Parting Line Defects
Challenge: Overmolding sometimes causes excess material (flash) at parting lines, leading to poor aesthetics and additional finishing costs.
Solution: Ensure high-precision tooling and optimal clamping force. Regular mold maintenance and inspection can cut defect rates by half.
Cycle Time and Production Efficiency
Challenge: Overmolding is naturally more time-intensive than single-material molding.
Solution: Use automated part handling between molding stages and optimize cooling times. Some manufacturers see a 15–25% cycle time improvement with robotics integration.
Bonding Failures Under Stress
Challenge: In applications like automotive seals or medical grips, repeated stress may cause delamination.
Solution: Incorporate mechanical interlocks into the substrate design. Even if chemical bonding weakens over time, the physical interlock maintains structural integrity.
