Small springs can be difficult to handle with automated assembly equipment, but large springs also present challenges.
Small springs can be difficult to use with automated assembly equipment, especially if they are particularly delicate or have a small wire diameter. But, large springs can also present unique challenges to engineers, depending on the way they are fed into the system.
“Tiny springs are usually more difficult to deal with not only because of size, but also because the process speeds for small springs are typically higher than [with] larger springs,” says Rick Amendolea, president of Centricity Corp. “[However], size is not always the issue. Whether small or large, if springs do not tangle, orientation is not a concern, and you can pick and place a spring with two-point contact, your automation project has a good chance of success.”
Large springs can cause big headaches for enginerers if they’re used in the wrong application. “Automobile thermostat springs can be harder to feed than a light bulb filament spring, if you try to handle it wrong,” explains Carl Nelson, president of Performance Feeders Inc.
“The extent of handling difficulties is usually determined by the spring geometry,” adds Michael Limb, president of Spring Design Consultants. “Spring size does not, by itself, cause tangling. Open coils and protrusions do.”
However, smaller springs can be more difficult to work with. “If tiny springs are being used in a manual application, the operator might be required to use tweezers or another gripping device to pick up the springs,” explains Jeffrey Given, president of Comtech North America. “In an automated application, springs are harder to detect in a tube and sometimes ring sensors are too sensitive to detect a spring passing through.
“In addition, the light weight of the springs can cause problems when feeding them,” Given points out. “In contrast, a very large spring can be too heavy to feed in a tube and a robotic gripper or vibratory track of some kind must be used to transport the springs. Typically, small-to-medium-sized springs are the easiest to work with. However, there are solutions to handling all shapes and sizes of springs.”
The degree of difficulty often depends on how tiny the springs are. For instance, “anything less than 0.04 inch in diameter or 0.125 inch long would be difficult,” says Nate Sornborger, engineering manager at Arthur G. Russell Co. “After that, the small ones are often easier because the feeder types available are more varied. Large springs often can’t have tight groups of coils due to performance issues, so they end up tangling.”
“Springs with small wire diameters are especially sensitive to back pressure,” adds Kate Stiltner, technical writer at JR Automation Technologies LLC. “The pressure of the springs in the escapement can cause the first spring to compress, making placement more difficult. Small springs are harder to separate in the escapement, costing valuable time and effort.
“Large springs can also present a challenge,” explains Stitlner. “Larger springs that are blow-fed to a part can require a large volume of air to drive them to the part, driving costs up and producing a lot of noise.”
With Springs, Size Matters
June 1, 2010