March 5, 2019
When compared to mechanical fastenings such as nuts and bolts or spot welding, adhesives often perform better. Modern adhesives create a high-quality joint, often at a lower cost, with less labor and no damage to the substrate. Recently there have been many improvements in polymer cure technology and these improvements have made the adhesives more ‘’manufacturing friendly.’’ The key benefits of adhesives over mechanical fasteners are they resist corrosive liquids, provide electrical insulation, boost impact resistance, prevent vibrational noise, decrease inventory cost and make automated manufacturing easier.
Electric motor manufacturers use adhesives and sealants to improve performance, simplify the manufacturing process and reduce costs. The products used include thread-lockers, gasket products, magnet bonding adhesives, retaining compounds and instant adhesives. Below you can learn about each of these product types and see what specific grades the adhesive experts at Hernon Manufacturing recommend for common applications in electric motors
Magnets in electric motors provide a good example of how adhesives can be used for brittle substrates and are typically assembled by applying adhesives. While mechanical fasteners create focused stress points, adhesives disperse the stress over the entire bonded area. There are different types of adhesives for magnet bonding applications that can achieve a bond strength higher than the magnet tensile strength. These adhesives are selected according to the need of the application area. The performance criteria differentiating these adhesive types are typically the curing time, temperature resistance, fixture speed, gap fill, and impact strength.
To assemble magnet segments in electric motors, Hernon recommends React® 727 because it produces a strong bond very quickly while maintaining strong vibration resistance. React® 727 is recommended for bonding magnets to housings but it can also bond magnet segments or ring magnets to rotors. The primary benefits of this adhesive choice are the speed of curing and ease of use. Simply apply a small amount on a clean dry surface of the magnet and hold against the second substrate for 30-60 seconds. Hernon’s Activator 63 can be used to further enhance fixture time.
Another common adhesive application in electric motors is retaining bearings and cylindrical parts. Assemblies of cylindrical or spherical parts, such as rotors, gears, bushings, collars, and bearings, can be accomplished with Hernon retaining compounds. The recommended grades of Hernon retaining compounds are Cylinlock 822 and Cylinlock 846. These compounds are high strength anaerobic liquids that cure to a tough plastic when air is excluded. These adhesives prevent corrosion, eliminate warping of the shaft and provide maximum contact between mating surfaces when cured.
Thread locking is another application for adhesive materials in electric motors. Thread locking adhesives work by filling voids between the threads on screws, nuts, and bolts. This process provides a high strength bond to supplement the natural holding power of the assembly. Threadlockers are anaerobic adhesives, so they cure in the absence of oxygen between close-fitting metal surfaces. Once cured, thread lockers have excellent moisture, temperature and chemical resistance allowing them to help seal and prevent corrosion of metal parts while also resisting vibration and the loosening of threaded assemblies.
Hernon’s family of thread lockers is called Nuts N’ Bolts. Nuts N’ Bolts grades 423 and 425 are two of Hernon’s thread lockers recommended for use in electric motors. Grade 423 cures quickly to produce a resilient seal with predictable torque values. This grade is also suitable for less active metals like stainless steel and plated metals. For a higher strength bond when using fasteners up to 1 inch in diameter grade 425 is suggested. It is tolerant of harsh and corrosive environments and designed to support heavy-duty applications such as studs into motor housings. Both adhesives have characteristic colors (blue for 423 to show medium strength and red for 425 to show high strength) that help when monitoring the application of the product during service.
When working with fasteners over 1’’ in diameter, Nuts N’ Bolts 429 is the ideal formula to use. However, if your task includes preassembled equipment and structures where penetration into fastener connection points is required, Nuts N’ Bolts 431 offers the required wicking properties. Wicking products allow thread locking without dismantling equipment. A wide selection of Nuts N’ Bolts grades are available to provide specialized characteristics and meet varying performance requirements. Formula properties such as viscosity, shear strength, maximum gap-filling, colors and cure time can be matched to meet specific needs.
Other areas of electric motors such as flanges and housings will need to be sealed with a gasket to ensure leakproof operation. A gasket is a mechanical seal that fills the space between two or more mating surfaces to prevent leakage. Hernon’s Gasketing compounds are formulated to provide instant sealing capabilities and excellent chemical resistance. Gasketing sealants offer benefits such as easy application, a precise match to unique shapes and lower costs over their pre-formed alternatives. Gasketing compounds are commonly anaerobic or silicone-based. Common applications include sealing the junction box with both motor stator and lid as well as the bell housing to the motor stator.
For sealing an area of the motor such as the junction box, Gasket Replacer 910 is recommended. Gasket Replacer 910 is an anaerobic compound formulated to provide instant sealing capabilities, a reliable long-term seal and excellent chemical resistance. For sealing bell housing to the motor stator, Hernon® recommends Silastomer 343. Silastomer 343 is a silicone-based Gasket Compound with a paste-like consistency that cures to a durable silicone rubber when exposed to moisture in the air. Silastomer 343 is suitable for metal, glass, wood, plastic and ceramic surfaces. 343 offers very high resistance to moisture and temperature and remains highly flexible.
Finally, when bonding plastic components and rubber tubing, cyanoacrylate adhesives are suggested. Hernon specifically recommends Quantum 135 with near-instant set time and high resistance to humidity. Quantum 135 is a very stable product with ≥ 2000 PSI shear strength. Quantum 135 is designed to seal plastic to metal on the shaft exit and it can also be used to produce fast bonds on the nameplates and other non-structural pieces.