Molded Cable: Design and Assembling Considerations

FACTS CHECKED BY  Jose George​

Choosing a cable that perfectly suits an application was a challenge earlier. However, the molded cables have changed the appearance and functionality of the lines. They are in use for residential and industrial purposes. Though they are so much in trend, people often are unaware of what they are. So, let’s know more about them.

Custom Harness with Male Bullet Con...
Custom Harness with Male Bullet Connector
UTP network cables

Image: UTP network cables

What are Molded Cable Assemblies?

Engineers use an over-molding process to give strain relief to the cable assemblies. All the molded cables mainly have two functions or uses:

  • Protection: The molded cables protect the different components of a cable. Any external elements in the connections can damage the wire and connector. Commonly, the wires and connectors need soldering for a proper connection. Any external elements in the connections can damage the wire and connector. There is inbuilt protection in molded cables, so soldered elements of the cable get a longer life span.
  • Resistance: Another critical property of molded cables is their ability to withstand harsh environmental conditions. These cables are resistant to strains, shock, constant movements, exposure to dust, and extreme weather conditions. Thus, these cables are more reliable and durable than other cables.

These two properties make them suitable for use where you need them.

  • Longer life span: Most cables undergo most movement at the cable exit point. As molded cables are more flexible, they are less prone to damage due to movements.
  • Less frequent damages: Molded cables give 360-degree strain relief with high pull strength. As a result, cables do not damage even after intense usage.
  • High customization: Industries that need a custom cable assembly use molded cables primarily. Users can make cables that suit their applications with such molded cables.

These cables’ protection and resistance features are highly suitable for home appliances and accessories. You can also find them in headphones, mobile chargers, power cords, laptop chargers, USB cables, and other devices.

Difference Between Assembled and Molded Cable Assemblies

The molded cables are different from the assembled cables.

  • Assembled cabling is commonly known as insert cabling, while molded cabling is over-molding.
  • In assembled cabling, one part fits inside a big component. On the contrary, pouring compounds encapsulate the injected part in over-molding.
  • In assembled cabling, the standard material is metal, while in over-molding, one can use plastic, PVC, PP, TPU, and Rubber.
  • Assembled cabling may require a special team to do the tasks, while for over-molding cabling, you need not have a separate specialist group.

Types of Molded Cables

Different brands in the cable industry offer different types of molded cables. However, mostly all lines fall in these two categories.

Standardized molded cables: These cables meet the critical uses of molded cables. Watertight compatibility, rugged performance, superior strength, and other technical specifications. These are low-cost cables, and you can find them in RF cables, HDMI cables, USB cables, etc.

Molded cables for a harsh environment: These cables have higher durability and reliability in extreme weather conditions. Industries or factories that are prone to harsh environments primarily use these cables. As they have a more complex design and greater material use, these cables are more expensive than the previous ones.

 Cable Assembly Over-molding Process

During the over-molding of a cable assembly, engineers inject molten material into a mold cavity under high pressure. The material used here is either thermoplastic or thermosets. The molding machine or press has a storage area (commonly known as a hopper) for the mold resin. 

To start molding, engineers put heating elements in the machine’s barrel at the hopper end, which melts the mold resin. The resin is mixed with desired colors and passes through the length of the barrel to reach the mold cavities. Inside the mold cavity, the material cools down and takes the design of the mold which may include part numbers, trade numbers, or company logos.

network cables connected to switch

Image: network cables connected to switch

Over Molding Design Considerations

Nowadays, tooling is becoming complex, and various materials are used in the process. As a result, you must pick all the parts very carefully. 

  • Molding material
  • The desired appearance of the molded part
  • Composition of the molding components
  • Operating parameters

The process of complex tooling is expensive, and once made, you cannot change the tooling. Thus, sometimes, engineers create a 3D printed model of the mold to test its form and fit.

Cable Overmold Tooling Materials

Photopolymers are used in the cable molding process. The availability of 3D printing has made the use of photopolymers easier. 

Another critical tool in molding is an injection molding machine. The molding machines are classified according to their tonnage. Cargo is the force the engine uses to keep the molds closed, and it means that a device with an enormous capacity can produce more significant molded parts.

Yet another tool in the process is the mold that manufactures the molded part. Molds are available in different materials depending on their exposed environment. However, the more detailed mold you want, the more expensive it will be. If a mold has to face thousands of molding cycles, the metal should be hardened steel. Even though hardened steel is costly, it gives a longer life expectancy. For a mass production environment, mainly steel molds are used.

Apart from steel, industries also use aluminum to make molds where molds face a limited number of cycles. Though it has a short life span, it offers better malleability and low tool fabrication costs.

When choosing a material to make the mold, one must consider that material to be molded. Industries use thermoplastic resins for steel or aluminum molds. However, when the resin material is liquid injection type like silicone, the mold should be hard as steel to hold that liquid.

You can also use 3D printed material molds if the cable quantity is less. 3D molds are cost-effective and complete the process more quickly than complex tooling.

Single or Multiple Cavity Designs

Molds are available in single and multiple cavity designs. As the name suggests, there is more than one cavity in multi-cavity, and every hole should be identical in design to this mold. If not, such mold designs can create issues like running of resin in differently designed holes without leaving gaps.

Firstly, the resin reaches the heated barrel through the hopper during the molding. The heated barrel melts the wax. As a result, the heated resin, forced by the screw, reaches the end of the barrel. This accumulated resin is the amount that will fill the mold’s cavities. This amount is commonly known as a shot. The shot can fill the hole within seconds.

The injection applies pressure to the shot until the resin cools and solidifies at the entrance gate. As the entrance is the smallest part of the mold, it is the first to solidify. Water and oil circulate in a series of openings to make the cooling process quicker. After the wax cools down, the injection screw prepares itself with the next shot after removing the cooled resin. 

Pre-mold and Overmold Designs

In some applications, you may require molds in two forms, i.e., pre-mold and oversold. The pre-mold refers to the already molded parts such as screws and pins, and one can put these parts in the mold cavity when it is empty. During the oversold cycle, the resin flows into the hole and solidifies around them.

Industries use such a process when an oversold needs to have screws to fix connectors to other installation components properly.

wire cables

Image: wire cables

The Appearance of the Finished Product

After the molding process, there may be a few marks or blemishes on the finished product. The dimensional difference in mold tool or wear and tear of mold tool results in such defects. You cannot avoid these blemishes but only minimize them with tightly designed mold tooling. 

Conclusion

Cable assembling and molding are evolving each day due to different materials and advanced technology. Almost all industries and applications use molded cables in different environmental situations. If you are looking for molded cable assemblies, you can contact us for more information or request a quote.

Get a free Cable Assembly Quote.