What is TPE Overmolding?

TPE  overmolding generally refers to the injection molding process where TPE materials are molded onto a second materials, typically a rigid plastic such as PP, PS, ABS, PC and PA. It can increase comfort touch, anti slip and impact resistance performance of finished products.

Two injection molding processes commonly used for the production of overmolded products are insert molding and multi-shot injection molding. Insert molding is the most widely used process where a pre-molded insert is placed into a mold and TPE is shot directly over it. Its advantage is that it uses conventional single shot injection molding machines for TPE overmolding, saving the costs of purchasing new machinery.

Multi-shot injection molding, also known as multiple material or two-shot molding, requires a more advanced injection molding machine that is equipped with two or more barrels, allowing two or more materials to be shot into the same mold during the same molding cycle. Manufacturers will select multi-shot injection molding to reduce cycle times, achieve parts with superior quality and reduce labor costs.

Notices for TPE overmolding:

  1. Take the compatibility of TPE and rigid plastic parts into consideration;
  2. Avoid sharp corners in the product design to improve the adhesion of TPE to rigid plastic parts;
  3. Use appropriateair venting to prevent air from in the mold cavities;
  4. Keep the proportionof TPE’s flow length and product thickness below 150:1;
  5. Achieve balance between TPE’s thickness and expected touch;
  6. Control the temperature of molten TPE to ensureadhesive effect;
  7. Perform special processing for smooth surfaceto increase the contact surface between TPE and rigid plastic parts, thereby strengthening adhesive effect;
  8. Use TPEwith excellent flowability, because the thickness and dimension proportion of TPE overmolding is very small and TPE is usually required to flow through long paths and thin-walled areas to fill molds;
  9. Use good adhesives.


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