Molding of cable assemblies requires a level of technical knowledge and production expertise that a limited number of cable manufacturers have in house. OEMs looking for molded cable assembly manufacturing partners are rightly very stringent in selecting the right company to build their cable designs because of the experience and equipment required to produce molded cables with consistent quality since there are many variables that can impact production runs and quality.
The key things to look for in molded cable assemblies are:
- Well thought-through design that is both functional and manufacturable;
- Tooling design that allows for consistent quality in production;
- Manufacturing practices and processes that reliably produce quality molding shots, and ultimately great quality cables;
- Expertise in encapsulation for applications where a PCB or other components are being over molded. Encapsulation is an advanced process that requires engineering expertise to ensure the PCB or components are not damaged in the molding process.
- Cable and tool-making engineering expertise to support an OEM’s requirements and manage all the technical issues that come with complex molding processes.
A molded cable primer:
Cable over-molding is a process used to encapsulate cables, connectors, or wire harness assemblies with a protective material, usually a type of plastic or rubber. This method improves durability, environmental resistance, and aesthetic appearance while providing strain relief for the cables. Over-molding is common in industries like automotive, medical, electronics, and consumer goods where robust cable assemblies are required. Here’s an overview of the process:
- Cable Preparation
The process starts by preparing the cables and connectors. This involves cutting the wires to the desired length, stripping the insulation, and assembling any necessary components, such as connectors, pins, or terminal blocks. The connectors may need to be soldered or crimped to the cable ends, depending on the design.
- Mold Design
A mold is designed based on the specifications of the final product. Molds can be single-cavity or multi-cavity, depending on production volume. They are usually made of metal, such as aluminum or steel, and shaped to create a precise encapsulation around the cable and connectors.
- Loading into the Mold
The prepared cable assemblies are carefully placed into the mold cavities, ensuring that the connectors and wires are positioned correctly. Proper placement is crucial to ensure uniform coverage and to avoid any misalignment during molding.
- Injection Molding
The over-molding material, often a thermoplastic elastomer (TPE) or thermoplastic polyurethane (TPU), is melted and injected into the mold under high pressure. The molten material flows around the cables and connectors, filling any gaps and creating a smooth, uniform coating. The choice of over-molding material depends on the application, temperature resistance, and flexibility requirements.
- Cooling and Solidification
Once injected, the material is allowed to cool and solidify within the mold. Cooling times vary depending on the material used and the complexity of the mold. Some molds may incorporate water channels to speed up the cooling process.
- Mold Ejection
After the over-molded assembly has cooled and solidified, the mold is opened, and the overmolded part is ejected. If necessary, a release agent may be applied to ensure easy removal from the mold.
- Inspection and Testing
The finished cable assembly is visually inspected for defects, such as voids, flashing, or incomplete fill. Additional testing, such as electrical or environmental testing, may be performed to ensure the cable meets design specifications.
- Secondary Operations (if needed)
Secondary operations may include trimming excess material, labeling, or adding protective coatings. For complex assemblies, additional over-molding stages might be required to create multi-layered structures.
Advantages of Over-molding
- Enhanced Durability: Protects against moisture, vibration, dust, and chemicals.
- Strain Relief: Reduces the likelihood of damage at the cable-connector interface.
- Improved Aesthetics: Provides a clean and professional finish.
- Customization: Can include custom shapes, colors, and labeling.
Applications
- Automotive: Wire harnesses, sensor cables, and connectors.
- Medical: Cables for diagnostic devices, sensors, and handheld instruments.
- Consumer Electronics: Headphones, charging cables, and USB connectors.
- Industrial: Harsh environment connectors and equipment wiring.
This process requires precise design and control of material flow, cooling, and tooling to produce high-quality over-molded parts that perform reliably in their intended application.
For more information on molded cable assemblies, the process and how to successfully design a solution for your application, please contact Merit Cables to set up a consultation session: www.meritcables.com