Generally, overmolded cables have exhilaratingly improved the design and functionality of cable assemblies.
Currently, design engineers are applying prototype technology instead of the traditional manual process.
The former enables manufacturers to 3D print tools and test their production level and functionality before the final manufacture. In this way, industries save material, time, and money.
That aside, we have captured the over-molding process, its applications, benefits, and benefits in this article. We hope you gain a broad insight.
Table of Contents
- What is over-molding?
- 6 Benefits of Overmolded Electrical Assemblies
- Cable Assembly Overmoldering Process
- Overmolding Desing Considerations
- Common Applications
- Conclusion
What is over-molding?
It is an injection molding process that involves using at least two materials to merge a connector and wire into one part.
Manufacturers carry out the procedure by inserting the cable assembly in a mold. Then, they cover substrates (first materials) using other elements.
(Plastic injection mold mass)
The process needs either:
- Overmold materials that employ a two-shot/multiple-shot or a single-shot (insert molding) technique.
- Or a hard plastic component that manufacturers use a TPU layer to overlay them.
Overmolded/over-molding cables are complete cable assemblies with a single piece of combined connector and wire.
After placing the cable assembly inside molds, the manufacturers will inject a molten plastic element into the space left by the mold.
On cooling and solidifying, the plastic will adopt the mold’s shape and enclose the joint section between the wire and connector.
6 Benefits of Overmolded Electrical Assemblies
They include:
A quick and automated process
Purchasing an automated over-molding machine will simplify your work. Essentially, you’ll only create the mold designs, then program the machine to carry out the remaining task.
The machines usually take a short time, even 30 seconds, to over-mold about two connections. Consequently, it increases output while reducing labor fees.
Upgrade lower-cost parts
The over-molding process produces sturdy and weathertight seals that encapsulate electrical components.
As such, building superior electrical assembly may only need less costly parts. An instance is in cases where sealed connectors are more expensive than unsealed connectors.
At the end of the over-molding, you’ll have a robust seal connection. Therefore, getting a cheap unsealed connector will be ideal.
Cost-effective molds
A mold has a bottom and top piece encompassing components meant for over-molding.
You may need a simple machine-prepared piece of aluminum to acquire the shape necessary for protecting PCB or electrical connection.
Even after creating the mold, you can reuse or store it.
Shield from shock and vibration
Vibration and shock are danger signs to electrical components since they contribute to mechanical failure.
Hence, making over-molded cable assemblies that can withstand the two destructive elements is crucial.
Manufacturers ensure there are no gaps left around internal components to achieve this, which also means avoidance of unnecessary component shifts.
Increase strain relief
If you’re in a setting where you constantly move or plug/unplug electrical assembly, your electrical connections will wear out over time.
With an over-molded system, you’ll receive more flexibility and reduced strain compared to traditional protection methods like backshell connectors, potting, and heat sinking.
(Heat sink protection)
Increase IP rating
Over-molding cables generate a material bond within connectors, cables/wires, and PCBs.
Then, the bond culminates in a watertight seal that prevents debris, dust, or dirt from interfering with the electrical components. An over-molded cable assembly can attain IP69K, IP68K, and IP67K standards.
Cable Assembly Overmoldering Process
The over-molding process is direct and involves many steps shown below.
Cable Overmold Tooling Materials
A couple of materials you can use consist of the following:
Thermoplastic polyurethane/TPU – Compared to PVC, it has several color varieties and a smoother texture.
It also has a higher heat tolerance rate, meaning it can withstand temperature changes and is more pliable than Polyvinyl chloride.
(TPU material)
Polyvinyl chloride/PVC – It is the most commonly recommendable and applicable over-molding material.
Despite being a flexible material, it’s an amorphous thermoplastic thanks to its rubber-like and soft texture. Thus, using it seems controversial.
For other materials, you can use photopolymers to inject simple molds since they’ll enable you to mold lower-temperature resins in a few molding revolutions.
Single or Multiple Cavity Designs
You can design a mold with multiple or single cavities.
Multiple cavity mold:
Manufacturers design and produce identical cavities to produce many molds in one cycle. Unidentical multi-cavities exist but are problematic when filling air gaps and voids.
Process
Usually, manufacturers deliver resin materials into heated barrels via hoppers during molding.
As the screw receives the forces and actual heating, the now mixed plus softened resin will approach the mold tooling.
As the resin (now termed as shot) build up at the barrel end, it’ll leave some allowance for its anticipated shrinkage.
The process gradually continues with the injection ram/screw applying pressure to the shot until all cavity gate resin cools down and hardens.
Since the entrance/gate is the slimmest portion of the molding machine, it’ll harden first.
After the solidification, manufacturers remove the resin, and a new cycle commences in preparing another shot.
Circulating oil and water is effective in aiding the cooling process. Manufacturers feed the combination into a mold tooling through channels/openings.
Then, they use metal finers or pins to remove the fully molded resin.
Pre-Mold and Overmold Designs
Overmold applications differ in requirements in that some may require a mold with two pairs, over-mold and pre-mold.
A pre-mold will have machined parts like pins or screws, or they could previously molded compacted segments.
You can place them in the cavity of an empty mold. During an over-mold cycle, the resin will flow through the pre-mold and solidify it.
Importance: During pre-mold, parts like screws help tightens installation components like connectors in over-mold assemblies.
The appearance of the Finished Product
Generally, you’ll find blemishes and marks on the final product after an over-mold process.
It could be due to visible marks as the resin gets through the entrance, worn-out mold tooling, or dimensional differences in the mold tooling.
To avoid them, manufacturers place entrances in less noticeable cavity areas.
Alternatively, when designing the mold tooling, they specify tight dimensional tolerances.
Overmolding Desing Considerations
Normally, engineers design cable assemblies while considering a bend or strain relief.
Therefore, in the over-molding process, they will use grommet equipment in areas where installation would go through an opening/housing.
Also, the grommet shields the contact and termination points by covering the connector backshells.
(Grommets)
As such, when there’s increased tooling complexity and a heightened number of required materials in the over-molding process, manufacturers must cautiously design the parts receiving injection molding.
Other considerations:
- Operating parameters of the molding equipment.
- Constituent of the molding material.
- The final appearance of the needed portion after molding completion.
- Materials used for molding.
Note: A 3D printed model is ideal for vast production as it is cost-effective and efficient.
Common Applications
Some of the most common applications of customized over-molded cable assembly include:
- Industrial and OEM: Industrial environments usually have harsh conditions. Luckily, over-molded wire and cable assemblies can withstand the circumstances.
- Solar and wind energy: These are alternative clean energy systems that are currently popular. The wiring systems must be robust to maintain durability in external and internal environments.
(Renewable solar and wind energy)
- Gas and oil: Industrial facilities like the oil field and processing plant that deal with gas and oil require effectively working cable assemblies. As such, the resulting equipment and machine should function efficiently in a continuous tear and wear environment or near chemicals.
- Military and defense: This sector often operates in different and varying types of environments. Some could be harsh, others dangerous. Therefore, custom over-molded assemblies enable machinery/equipment to cope with the environment.
- Medical equipment: Overmolded wiring systems ensure medical tools and equipment are sturdy against round-the-clock wear and flexing. Furthermore, they help the tools remain stable during the frequent sanitation processes needed for keeping good hygiene standards.
(Medical equipment)
- Household electronic products: Home electronics have adjustments, installations, and flexion several times. Having a good wiring system thus is beneficial.
- Car: Automotive assemblies should persevere under chemicals, vibration, dust exposure, and heated surrounding inside vehicles.
- Correspondence: Wiring in communication systems should overcome inclement weather to achieve steady and excellent performance.
Conclusion
In summary, over-molding uses two materials to connect a connector and wire.
The process has several advantages, such as customization, reduction of human error, water resistance, shock/abrasion resistance, and a simple installation process.
Often, you’ll see its application in the medical, military, communication, and motor industries, to mention a few.
