molded rubber bellows

Molded Rubber Bellows: Standard and Custom Products

Rob PruynCustom Products, Products and Services, Standard Products

Molded rubber bellows are flexible seals that protect mechanical structures from the environment while permitting a range of motion. They are used in industrial, transportation, and many other applications as a protective covering against dust, water, oil, grease, chemicals, and environmental elements such as mud, splatter, and snow. Rubber bellows can also reduce noise, resist shock and vibration, and withstand sunlight and ozone while remaining flexible at changing temperatures.  

The Rubber Group uses injection, transfer, and compression molding to produce standard and custom rubber bellows in a range of materials, shapes, and sizes. Keep reading to learn more about our flexible rubber bellows or request a quote if you’re ready to place an order. Whether you need a large diameter bellows or a small one, we mold quality rubber products and offer value-added services such as design assistance and help with material selection.

Convoluted Rubber Bellows: Standard and Custom

Molded rubber bellows have a coil-like structure with a series of convolutions, or peaks. When the bellows is open or extended, these convolutions are separated and the non-convoluted surfaces between the peaks is visible. When the bellows is closed or retracted, the convolutions are bunched closely together. The bellows itself can be tapered at the ends or have a uniform diameter. Most convoluted rubber bellows are rounded, but products with a squarish or rectangular design are also used. 

Molded rubber bellows are similar to expansion joints and convoluted tubing but have a larger extended-to-retracted ratio for tighter compression and a more dynamic range of motion. Compared to these other rubber products, molded bellows need to support greater flexing. Flanges, collars, and back-up plates can be used for attachment, so it’s important to consider the mounting method for either a stock rubber bellows or a custom product.     

Molded Rubber Bellows: Materials and Applications

Molded rubber bellows are usually made of nitrile, neoprene, silicone, or natural rubber. Each type of elastomer has different performance properties.

  • Nitrile rubber bellows combine very good abrasion resistance with good tensile strength.
  • Silicone rubber bellows lack abrasion resistance but have good rebound resilience.
  • Neoprene rubber bellows have good tensile strength, elongation, and tear resistance.
  • Natural rubber bellows have good tensile strength and tear strength.

During material selection, it’s especially important to consider all of the environmental elements that the molded bellows will contact. For example, nitrile offer excellent oil and solvent resistance but has poor flame resistance. Neoprene provides only moderate resistance to alkalis and acids, but offers strong resistance to sunlight, ozone, and weather. Silicone resists a wide range of temperature but isn’t recommended for use with oils or gasoline.

The end-use application also drives material selection. For example, an automotive bellows that’s installed on the underside of vehicle needs to resist water, a range of outdoor temperatures, automotive fluids, and road salt. A joystick bellows that’s used inside heavy equipment doesn’t face these same conditions, but still needs to withstand repeated flexing. A universal bellows, or universal expansion joint, is used to  absorb motion in multiple planes.   

Ask The Rubber Group for Flexible Rubber Bellows

The Rubber Group is an ISO 9001:2015 and ITAR registered company that serves companies ranging from startups to OEMs from our headquarters in Rochester, New Hampshire (USA). Whether your need custom rubber bellows or standard products, we’re ready assist you. Contact us to get started.