Made from conductive metal wire wrapped or coiled into a specific diameter, encapsulated coils, like all electric coils, are electromagnets or magnets that are only activated to magnetism when introduced to an electrical current. Electric coils provide either movement or electric current transformation through electromagnetism.
An outer casing is used on electric coils that require protection from harsh environmental conditions such as moisture, salt, oil or vibration; with nothing to protect delicate copper coils from the elements, an electric coil’s conductivity might be easily lost. Encapsulated coils and molded coils solve this problem in overlapping ways: molded coils are enclosed in injection molded or thermoplastic coverings that seal the entire coil unit, while encapsulated coils more often use liquid or thermoformed polymer epoxies.
While these two overlapping types are often the same, molded coils often refers to coils that are encased in hard, hollow thermoformed or injection molded plastic casings; encapsulated coils are often molded into liquid or thermoformed epoxies, causing the coil to become one with its casing.
Encapsulated coils often offer better protection from harsh weather, oil and vibration than molded coils, since encapsulated coils are often dipped or thermoformed into sealing liquid epoxies; epoxies like silicone rubber offer vibration protection that injection-molded casings do not. Encapsulated coils can also be heat-treated after production, a process that sinters the encapsulating plastic part with the molded coil inside, providing superior protection to the coil.
While many encapsulated and molded coils can be cost-effective alternatives to larger, more complicated structures, the tooling costs of manufacturing thermoformed or injection molded plastic casings often rise above the costs of impregnated coils, which have wire directly encased in an epoxy or laminate before it is wound; impregnated coils have no need for outer casings and therefore require little or no tooling.
Manufacturers choose molded coils, encapsulated coils, impregnated coils or custom coils, whichever best fits the application and manufacturing process at hand.