Molding Materials: One Over Another

By George Allman on 14 November, 2018

molding-materials-potted- connectors 2

Molding protects the connectors of a wire assembly from a variety of potential harmful influences. These include environmental factors such as water and chemical damage, as well as abrasion and other physical damage in service. Using the best material for the job also ensures the best possible adhesion for the components, yielding reliability and longevity of the end product. The choice of molding material used is directly related to the desired function and level of performance, and utilizing the best materials in the industry---such as urethanes , silicones, and epoxies---ensures the highest quality of assemblies according to client needs.

One factor that manufacturers must take into account when choosing the best molding material for the job is whether the material will provide good adhesion. As part of this process, it is important that the assembly is cleaned, treated, and primed to be ready for the application of the potting material. These preliminary steps ensure the highest level of adhesion possible, which is vital to the best application of the molding. With good adhesion, the wires and connectors will bond strongly together and work as a single part.

Polyurethanes are commonly-used molding materials. These types of materials are an excellent option where a cost efficient, higher performing product is required. Often used in military applications such as missile and torpedo systems, polyurethanes generally provide good adhesion of the wires to the connectors, as well as providing strain relief within the wire bundle. However, these polymers have the drawback of being more rigid, and are not always appropriate for some applications where flexibility is required.

Silicones are a common industry material, adding a soft and flexible layer of protection to a wiring harness. Silicones are resistant to temperature extremes and offer excellent adhesion, making them useful as sealants or coatings. Often, silicones and urethanes are used in tandem to provide first; a soft layer of adhesion and sealing, and then a more rigid and durable layer of protection. Silicone is used in a wide variety of applications, from military to commercial assemblies.

Epoxies are another commonly used family of materials. Unlike silicones and urethanes, epoxies can be difficult to mold with, as they are not reworkable once cured. However, epoxies are exceptionally durable, rigid, and chemical resistant, making them perfect for certain functions. Epoxy inks can also be used to mark different mechanical parts such as metal plates or urethane connector bodies. The durable and stubborn nature of these inks means that this labeling will not easily wear off.

Compounds can be an excellent option for transferring or compression molding various cable harnesses. These compounds include include neoprene, Viton, and EPDM. All of these compounds offer various levels of heat and chemical resistance, while still providing the durability, abrasion resistance, and pliability needed for certain demanding applications like mining equipment, rail transit, and rocket motor harnesses. In short, compounds are made up of a variety of materials that provide a myriad of applications across a wide range of industries.

It is imperative that the molding material used is not only appropriate for the assembly function, but that it is also compatible with the materials of the assembly itself. Selecting compatible materials and utilizing the correct methods to ensure proper adhesion are key to providing the most robust molded assembly designs possible.

Contact Liberty today with any questions that you may have. 

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Topics: Operational Efficiency, Risk Mitigation, Quality Control, Quality, Materials Performance, Design, Design Challenges

Author: George Allman

George Allman is a Manufacturing Engineering Supervisor that has been with Liberty for 21 years. He works primarily in process and fixture development within Liberty’s Mil/Aero Business unit, and also helps to support new business growth and development in various capacities. He is a member of the Society of Manufacturing Engineers, serves as an advisor/mentor to local STEM student groups, and is a frequent speaker and contributor at various events within the Additive Manufacturing community.
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