The Complete Guide to Cable Overmolding: Benefits, Process, and More

Cable overmolding has improved the reliability of cable assemblies exposed to harsh conditions like moisture, vibration, and constant flexing. It also offers aesthetic benefits, allowing for customized cable shapes with engraved logos, trade names, emblems, part numbers, or insignias.

This process was once costly, but 3D printing has changed that by making it easier to create overmold models for form and fit testing before investing in complex tooling. Here’s a complete guide to cable overmolding, covering the process steps, benefits, materials used, and common applications.

What is Cable Overmolding?

Cable overmolding is a type of injection molding. It uses one or more materials to fuse a wire and its connector into a single, permanently sealed part. This seal protects the wire-connector joint from moisture, vibrations, and repeated flexing.

Traditionally, cable harness manufacturers used backshells and heat shrink tubing to protect these joints; however, these methods were less durable and limited the joint’s shape, size, and material options.

Cable overmolding offers greater flexibility in terms of shape, size, and hardness of the joint.

How Does Overmolding Benefit Cable Assemblies? 

Striking the right balance of flexibility, rigidity, and tightness in the cable overmold is key to the reliability, safety, and durability of the cable assembly. When done correctly, overmolding delivers these benefits.

Prevents Tampering

Human tampering can occur either accidentally or intentionally for purposes such as sabotage. Cable overmolding adds an extra material layer to make it more difficult for unauthorized personnel to cut or unplug the connector, which can be accidental or intentional. In critical installations, this sealed joint can include metal or PVC threads enclosed in the overmolding material, making cutting or tampering even harder.

Improves Efficiency and Durability

Cable overmolding protects the cable-connector joint from extreme external conditions, and by doing so, this cocoon enhances the durability of the cable assembly while also improving its efficiency. This is because it keeps out the elements that can downgrade the electrical or signal transmission performance.

Better Insulation

The material overmolded on the wiring harness sits on top of the cable and connector’s existing insulation, which means double or triple protection from electrical shorts or EMI.

Tolerates Harsh Environments

Overmolded cables can withstand harsh environments, including sterilization, exposure to dust and moisture, abrasion, extreme temperatures, and chemical exposure. The process involves selecting the most suitable material to use for the overmold that can withstand these conditions.

Creates Secure Cable Connections

The additional insulation material can also be used to provide strain relief and increase the pull strength. Without it, the joint would simply come off after minor pulling or twisting. The overmold works by keeping the joint intact on the inside while it flexes on the outside, ensuring 360 ° strain relief and allowing for pulling without snapping.

Withstands Shocks and Vibrations

By using soft materials to create the overmold, the cable can withstand shocks and extreme vibrations commonly experienced in vehicles, industrial machines, and similar environments. Over time, wear and tear will occur, but this will be in the overmold material, leaving the cable-connector joint intact. Essentially, the overmold is a sacrificial material, just like bushes in cars.

Flexibility

The outer casing of the wiring harness joint, known as the overmold, serves as a buffer or support system, ensuring the cable only bends to a certain extent. It also limits the pulling pressure that can stretch the joint, making it remain intact during operations.

Improved Organization

Cable overmolding improves wiring organization in two ways. First, it creates secure joints and wires in a compact form factor, simplifying installation in tight spaces. Second, the overmolds can be formed in different colors to enable color-coding during installation and easy identification during maintenance.

Customization

Customization is one of the less obvious advantages of overmolding because it is mostly cosmetic. For instance, the color, shape, size, and finishing can be customized to suit your preferences.

But customization can also be functional. Parameters such as color can be used for color coding, while the material can be selectively chosen to suit the application. The logo can also be included for marketing and brand identity purposes, flanges for attachment points, and the shape can be altered to fit into narrow areas. Additionally, LED indicator lights can be included to ease identification during repairs. 

Meet IP Certification Standards

In some cabling applications, such as those in marine environments, an IP certification is required for dust and water resistance. Cable overmolding enables this certification by sealing the exposed areas along the wiring harness, which is on the connector joints.

How Does The Overmolding Process Work?

The overmolding process is split into four parts.

Mold Design

There are standard mold designs with ready-made molds. But some customers prefer having a custom wiring harness overmolding, which means the mold must be designed from scratch. It can have a custom shape, size, company logo, writings, part numbers, or any other aesthetic or functional feature. The goal of the mold design step is to ensure the overmolding meets the customer’s specific requirements, operating conditions, and applications.

Mold Preparation

Once the design is ready, it must be created into a model, which is more cost-effectively done using 3D printing. This model is used for form and fit testing, after which it is used to develop the mold cavity. Of course, the customer must sign off on the approval before the final mold cavity or hard tooling is built. Mold cavities are usually made using aluminum or hardened steel, with the latter being more expensive but more durable.

Material Selection

The next step is to select the most suitable material for the job, which is chosen based on specific requirements, such as waterproofing, vibration resistance, oil and chemical resistance, and strain relief. Each material has distinct properties, which impact the quality of the overmold in its intended application area. Materials can also be mixed to form a compound that provides the desired results.

Molding

Overmolding is injection molding. It pushes molten material into a mold cavity around the wiring harness-connector joint. Once cooled, it forms the overmold, matching the earlier 3D model with all custom features.

To achieve this, the injection molding machine has four main components:

• Hopper: Stores the mold material (resin).
• Screw-type plunger or injection ram: Pushes the material at high pressure through the barrel.
• Barrel: Contains heating elements to melt the material into a liquid. Colorants are also mixed here.
• Mold: Holds the mold cavity and wiring harness joint. The plunger forces the molten resin (and colorant, if used) into this cavity. Once cooled, the overmold solidifies around the cable-connector joint, capturing all the cavity’s details, such as shape, logos, and size.

After overmolding, the cable assembly is stress-tested for durability purposes.

What Materials Are Used in Overmolded Cables?

Material selection is the key factor in the cable overmolding process. Common materials include:

PVC

Polyvinyl Chloride is a commonly used overmolding material because it has a soft, rubber-like texture that provides superior flexibility. It is also resistant to chemicals, tension, weather, and flames. But this amorphous thermoplastic can be stiff and brittle when exposed to low temperatures.

TPU

Thermoplastic polyurethane is a superior alternative to PVC when exposed to high and low temperatures. It is also softer, more elastic, comes in a broader range of colors, and is resistant to oil, grease, and solvents. The catch is it is costlier.

Neoprene

Neoprene is costlier than TPU because it is a synthetic rubber (more expensive to produce). However, as a more premium material, it comes with its benefits, such as resistance to weather, ozone elements, UV light, oxidative elements, oils, and damage from broad temperature ranges, as well as tearing and twisting/flexing. Neoprene also resists burning better than hydrocarbon rubber materials.

Viton

Viton overmolds can withstand extreme temperatures, fuel cell immersion, and various fluids and chemicals at high temperatures. They are also resistant to harsh weather conditions, flames, and oxygen. But being a proprietary rubber material, Viton is quite costly and might not be readily available.

EPDM

Ethylene Propylene Diene Monomer is also a synthetic rubber like Neoprene, so it provides similar advantages. These include resistance to harsh weather conditions, heat, water, ozone, radiation, salt, glycol, synthetic hydraulic fluids, and oxygenated solvents. But it is cheaper. The catch is that it is less effective when resisting oil, solvents, and flames. Neoprene possesses better flame-retardant and flame-extinguishing properties.

Other Materials

Other overmolding materials to consider include:

• Thermoplastic Vulcanizate
• Liquid Crystal Polymers
• Polycarbonate
• Polyethylene
• Acrylonitrile Butadiene Styrene (ABS)
• Polypropylene
• Thermoplastic Rubber
• Technomelt
• Macromelt Rubber
• Polybutylene Terephthalate (PBT)

Cable Overmolding Applications

Cable overmolding is essential in the following applications.

Automotive

Wires in cars and trucks are consistently exposed to heat, vibrations, moisture, chemicals, oils, and low temperatures (during winter). Cable overmolding protects the wire-connector joints from exposure to these conditions.

Medical

Radiation, contamination, fluids, and physical damage (such as abrasion) are some of the hazards in the medical field to which wiring harnesses can be exposed. Overmolding with materials like EPDM and neoprene will protect the harness from harsh conditions.

Telecommunications

Cable overmolding in telecommunications provides strain relief, waterproofing, cable organization, and customization for aesthetics or functions such as color coding and branding, while increasing pulling strength and improving signal integrity (which can block EMI).

OEM

With OEMs, cable overmolding presents several advantages, including environmental resistance, strain relief, shock and vibration resistance, branding, aesthetics, and a reduced assembly time for the final product, as workers or machines won’t have to link the wires and connectors.

Oil and Gas

In the oil and gas industry, common hazards include high temperatures, flames, mechanical stress, and exposure to chemicals. Cable assemblies in this industry must withstand these conditions to ensure maximum durability and plant safety.

Home and Office Appliances

Cable overmolding is important in wiring harnesses used in home and office appliances to prevent shorting and tampering, provide strain relief, meet regulatory compliance standards, withstand wear and tear, and reduce product assembly time.

Wiringo: Advanced Overmolding Technology for Superior Protection

With our precision engineering and advanced overmolding technology, Wiringo’s cable assemblies provide superior protection from the elements, including dust, moisture, mechanical strain, radiation, EMI, and other hazardous conditions, making them suitable for various applications such as automotive, industrial, medical, OEM, oil and gas, and more.

Wiringo’s strength lies in our customization capabilities, whereby we work closely with you, our client, to pick the most suitable wires, connectors, and overmolding material that meet your application requirements. While delivering these tailored solutions, we ensure they meet the relevant industry standards for maximum reliability in demanding conditions. We have also streamlined our production process to ensure you get these overmolded cable assemblies in quick turnaround times, so your projects are always on schedule. Contact us to get one-on-one assistance for your overmolded cable assembly project, and we’ll direct you to our dedicated experts in this field to guide you through the design and production processes.