A flat metal strip is punched into circular disks.
The disks are formed into small cups. Then, these cups are degreased in a modern washing bay and annealed in a vacuum furnace.
A series of long draws transforms the cup into a seamless, closed-end tube of the highest quality.
While in the forming die, 1500psi of water pressurizes the inside of the tube as it is compressed, creating the corrugations.
The bellows are trimmed to size.
A final compression stage sets the bellows and gives it spring-like characteristics.
A traditional and popular bellows material with a low manufacturing cost, brass solders easily even with today’s lead free solders. Suitable for operating temperatures up up to 300ºF (150ºC), brass bellows applications typically involve an air medium. Examples include mechanical altimeters and thermostatic assemblies.
With a slightly higher tensile strength, better corrosion resistance and better electrical conductivity than brass, bronze also offers a low manufacturing cost. Bronze solders as easily as brass, but it can also be brazed for use in high temperature applications. Bronze bellows are often used in high-volume applications, such as appliances and HVAC equipment.
Beryllium copper (BeCu) has a superior tensile strength and electrical conductivity when compared to the other bellows materials. It can be soldered or brazed. Age hardened beryllium copper is often incorporated into a bellows assembly, which can then be heat treated for maximum dimensional stability. Beryllium copper bellows are often favored in applications requiring a small package size and demanding lifecycle requirements. Among these applications are aerospace systems and instrumentation.
A nickel alloy, Monel offers better corrosion resistance than brass, bronze or beryllium copper. Monel is routinely welded, though it can be brazed as well. With similar mechancial performance to bronze, Monel is often used in corrosive environments, such as those containing steam or salt water.
Bellows can be manufactured from a variety of stainless steels, with 300 Series steels the most common. Stainless steel has excellent tensile strength, making it easier to maximize stroke and minimize package size. Stainless steels also have excellent corrosion resistance in multiple environments and media. Typically brazed or welded, stainless steel bellows withstand high operating temperatures. Stainless steel bellows applications include electrical interrupters, power transmission systems and industrial controls.
Nickel is a hard material with excellent corrosion resistance. Electrodeposited bellows are made from nickel, but the material is also useful as a corrosion resistant plating for other types of bellows. Nickel is very widely used in aerospace applications.