Cable Molding: The Ultimate Guide

Once you have the right cable and the connectors, you must protect the junctions from liquid ingress. Heat-shrink tubing offers moderate protection from moisture ingress, while over-molding is a better solution. The article will discuss all about cable molding.

What is Cable Molding?

Cable molding is a manufacturing process that combines and seals wires with connectors, creating one unified part.

In cable molding, the injection molding process is an important factor, enabling the equipment to precisely control the critical tolerances to the external pressure and temperature. 

During manufacturing, a material is molded over the wires/cables as they are inserted into a non-insulated or insulated connector or raceway.

Continuously controlled hot-melted thermoplastic is used for over-molding to provide a consistent design and maintain the perfect balance between the flexibility and rigidity of the housing and cable.

Cable Molding Machine Understanding & Cable Molding Process

Also known as a press, the injection molding machine has a storage area called a hopper for mold resin.

The resin material is delivered via the hopper into the heating barrel during the molding process. Through the heating of the material and the force of the screw, the softened and mixed resin pushes forward to the molding tool. 

It’s then mixed with any desired colorant, and it transits the length of the barrel to the actual mold, where the colorant and resin mixture is forced into mold cavities. 

The melted resin collects at the barrel’s end, referred to as a shot. The shot is the amount of resin you need to fill the mold cavities and should include extra in case the resin shrinks. A cavity normally takes just a few seconds to fill.

The injection ram or screw keeps adding pressure to the shot until the resin at the gate to the cavity cools and solidifies, taking any features designed in the mold, such as trade names, part numbers, or logos.

The cavity gates are normally the narrowest/smallest part of the molding tool. Therefore, it’s usually the first section to cool and solidify. Once the material at the gate is solid, the injection machine cycles through the process and prepares another shot, awaiting another molding cycle. The resin in the mold cavities keeps cooling and is ready for removal once it solidifies.

To help the cooling process, you can circulate oil or water through the molding tool in a series of channels or openings. Once the resin cools to the point that it becomes fully solid, the mold tool opens, and you can remove the complete mold. Metal fingers or pins inside the tooling help you remove the complete mold. Once you remove the molded part, the cycle can start again.

Cable molding tools

Dies or molds are the actual tools used to manufacture molded parts. Molds are expensive to produce; the more detailed the mold, the higher the costs.

Tooling Material

Molds are made of different metals depending on how many cycles you plan to expose them to.

If you plan on using your mold in a production environment and expect to expose it to countless cycles, hardened steel is the ideal metal to use. Hardened steel molds are costly to manufacture. However, their longer lifespan and ability to undergo countless mold cycles before wearing out compensate for the cost. Steel molds are normally used in mass-production environments.

Aluminum can be used for molds that undergo a few cycles or prototypes to prove a mold design. Aluminum has a shorter lifespan compared to steel. However, its malleability results in lower fabrication costs. Most molds are produced using CNC (Computer Numeric Control) machines or electrical discharge machining processes.

The material you choose for the mold should match the material you plan on using for the molding itself. If your resin is thermoplastic, you can use aluminum or steel (stainless or hardened). If your material is a liquid injection type, such as silicone, your tooling should be hardened steel. 

For smaller volumes, you can create molds from 3D-printed materials to make small-quantity runs of cables or test the mold itself. This method is way more cost-effective and quicker than hard tooling. However, it can only be used for 50 – 100 cables.

Tooling Design

You can design a mold with one or multiple cavities. Each is designed and made identical in multi-cavity molds, producing numerous molds in one mold cycle. Multiple mold cavities could sometimes include non-identical cavities but with major design problems. Issues like resin flow into differently designed cavities without creating air gaps or voids.

Resins Used in Cable Molding

The most commonly used over-mold materials are thermoplastic, which is cheaper than other methods and enables facile side out and side movements of various cables.  Furthermore, it assists in uniting different components and cables and provides reliability and lift to the cable ends. 

PVC is the most acceptable and commonly used over-molding thermoplastic. However, it’s an amorphous thermoplastic. PVC features a soft rubber-like feel and impeccable flexibility.

TPU is softer than PVC and offers a variety of colors. It has a higher heat tolerance and is more pliable, making it stable even when exposed to high temperatures.

Benefits of Cable Molding


The materials used and mold configurations are controlled in the molding process,  enabling you to design a cable assembly tailored to the exact needs of your application. 


Molding ensures no gaps or spaces between components, preventing them from moving or shaking within your assembly. Further, a bond forms around cables and connectors, providing a watertight seal around cable assemblies. 

High-Compressed Assembly and Integration

Molding produces smaller assemblies compared to other methods, like mechanical back shells. This small size enables designers to minimize the size of their equipment or components.

Fewer Installation Errors

Since you don’t need additional assembly, you can quickly assemble your molded cable assembly using a simple process, minimizing the chances of human errors.  


For all your cable molding needs, contact Cloom, the leading custom wiring harness and cable assembly manufacturer.