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How to Encapsulate Wire Harnesses / Cables?

In the field of medical electronics, there are many active devices (such as high-frequency surgical equipment, blood dialysis devices, etc.), and most of these devices require secondary encapsulation of their wire harnesses. To effectively connect the wire harnesses with metal parts or other adapters, a secondary encapsulation process is needed, which has high requirements for the quality and appearance of the encapsulated wire harnesses. The encapsulated wire harnesses are responsible for the power distribution and signal transmission between various electrical and electronic devices.

1. Challenges in Wire Harness Encapsulation

Compared to other plastic secondary molding processes, the encapsulation of wire harnesses presents several challenges:

  • Wire harnesses are soft, making it difficult to effectively position them within the mold cavity and to prevent deformation under relatively high mold temperatures.
  • Choosing the right type of material to enhance the bond strength after encapsulation is crucial, especially when using thermosetting liquid silicone materials.
  • During encapsulation, preventing the formation of flash and ensuring that the cable surface is not damaged are also challenges.
  • Based on the actual product structure, it is key to disassemble components and pre-encapsulate structures to connect multiple parts in advance, achieving overall encapsulation of the wire harness.
  • The value of wire harnesses is relatively high, making it difficult to reduce waste from initial setup and to improve the yield of the encapsulation process.
  • Ensuring the stability of production cycles and material quality during the encapsulation process is challenging.
  • It is also difficult to improve production efficiency by implementing automation or local work fixtures based on the actual product characteristics.

2. Development Considerations for Wire Harness Encapsulation Products

  • At the development stage, the actual temperature resistance of the cable sheath should be considered, and cables with certain temperature resistance should be chosen to ensure they meet the temperature requirements for secondary encapsulation.
  • The choice of secondary encapsulation material should ensure good adhesion with the cable without damaging it.
  • In product design, when connecting cables with metal or other metal parts, consider the fastening method to prevent the plastic impact from breaking the connection during secondary encapsulation, rendering the product ineffective.
  • Avoid designing overly thick encapsulation features to prevent excessive shrinkage after encapsulation.

3. Mold Design Considerations for Wire Harness Encapsulation

  • Mold design should include a reasonable pre-compression value to seal the encapsulation without damaging the cable sheath.
  • The mold should have a reasonable positioning method for the cable to ensure it is not damaged or misaligned during encapsulation and injection molding.
  • Based on the actual product structure, necessary pre-embedding structures should be designed to connect the cable and metal parts in advance, reducing the difficulty of direct encapsulation.
  • Design reasonable work fixtures or automation to improve actual production efficiency and ensure cycle stability.
  • Design a reasonable part removal method to facilitate stable extraction after production.
  • Avoid sharp edges in mold design to prevent cable damage.
  • Consider how to effectively protect long cables within the mold cavity during mold design.

4. Mold Processing Considerations for Wire Harness Encapsulation

  • Mold processing should ensure smooth transitions at chamfered areas;
  • The pre-compression seal should have a smooth transition to prevent cable surface marks;
  • Adequate pre-compression should be allowed during processing;
  • Mold fitters should adjust the pre-compression based on actual conditions to avoid damaging the cable.

5. Injection Molding Process Considerations for Wire Harness Encapsulation

  • Ensure the cleanliness of the cable surface before encapsulation and the actual operation of the previous SOP.
  • Under the premise of ensuring the product is fully filled, use scientific trial molding methods to avoid excessive injection speed and pressure.
  • Set reasonable mold and material temperatures to prevent cable damage or deformation.
  • Ensure stable and consistent manual operation to maintain cycle stability.
  • After encapsulation, promptly circulate the finished products to prevent cable product accumulation and entanglement.

In summary, to produce high-quality wire harness encapsulation products, the selection of cables and encapsulation materials should be a priority in the design phase. Reasonable pre-compression should be designed at the initial mold design stage, and proper differentiation should be implemented during processing and mold fitting. Ensuring stable production processes and cycles will lead to relatively ideal wire harness encapsulation products.

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