What is Overmolding ? Overmolding used for
⚙️ What is Overmolding?
Definition | Process | Material Compatibility | Benefits
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🎯 Introduction to Overmolding
Overmolding is a specific method of plastic molding where plastic profiles are used as raw materials. Through the application of heat and force, they are transformed into desired shapes.
To meet special needs, many products are made by combining two or more plastic materials using multiple injection molding methods. This process is essential for enhancing appearance and functionality.
✨ Overmolding Features
- Soft Surface: Known for creating "soft-touch" surfaces on hard plastics.
- Two Molds: Usually requires two separate sets of molds.
- No Empty Spaces: Ensures solid bonding between the soft mold part and the hard main body.
- TPE Application: With the development of the TPE elastomer industry, overmolding has become mature, enhancing grip, touch, and aesthetics.
🌟 Advantages
Overmolding not only makes the device surface full of softness but also significantly increases product functionality and added value.
It eliminates assembly time, reduces secondary operations, and allows for creative color combinations.
🧪 Material Compatibility (TPE Formulas)
The key to successful overmolding is the adhesion between TPE and the coated material (Substrate). Here is a breakdown:
| Substrate Material | Characteristics & Tips | Temp. Range |
|---|---|---|
| PP (Polypropylene) | Very weak polarity, close to TPE (SEBS). Standard TPE works well without modifiers. | 170°C - 220°C |
| ABS / PC | Weak to medium polarity. Requires a modifier (TPU) in TPE formula for better adhesion. | 180°C - 230°C |
| PBT / PET | Semi-crystalline plastics. Require higher melt temperatures for bonding. | Higher than ABS/PC |
| PA6 / PA66 (Nylon) | Strong polar plastics. Requires high energy to form a weld layer. PA66 needs higher temps than PA6. | 230°C - 270°C |
⚠️ POM Overmolding Challenges
Although POM (Acetal) has a low melting point of 180°C, overmolding it is difficult because:
- High Crystallinity: Requires high energy to form a bond.
- Self-Lubricating Property: Makes it hard for TPE to adhere to the surface.
✍️ Summary
Understanding material compatibility is crucial for successful overmolding. Choosing the right TPE formula based on the substrate (PP, ABS, PA, etc.) ensures a strong bond and a high-quality product.
