If you ever want to hear a manufacturing engineer swear, just mention the word “springs.” The coiled components come in a wide variety of sizes, and they’re used in many mass-produced products, ranging from pens and syringes to valves and lightbulbs. But, tiny springs often cause big headaches when it comes to automated assembly.
Many engineers have horror stories about the pesky parts. “They’ve been a nightmare forever,” says Carl Nelson, president of Performance Feeders Inc. “Springs can easily get you in a lot of trouble. There are many variables with spring designs, and each application is different.”
Springs are often a very inexpensive component in an assembly. However, the problems created in detangling and handling them can greatly affect the productivity and efficiency of automated assembly systems.
“Springs are inherently difficult to handle for a variety of reasons,” explains Jeffrey Given, president of Comtech North America. “When handled in bulk, they have a tendency to get tangled together. This problem is magnified if the spring has open-end coils, which can result in the springs being corkscrewed into one another.
“Springs are different from most other components,” says Given. “They tangle, bounce and, depending on the design of the spring, need to be fed and oriented in a variety of positions.
“In an automated application, springs are loaded into a feeding system in bulk and many times must be separated before they are oriented and fed to the next step in the assembly,” adds Given. “If not careful, springs can be damaged by an operator trying to separate them during [a semiautomated] assembly.”
Tangled springs present the biggest challenge. If a spring can be separated, it can usually be fed in some way.
“One of the problems we face when feeding springs from bulk is keeping them separated when they are being queued up and escaped,” Given points out. “If the spring has closed ends, this normally isn’t an issue, but if there are open ends or if the spring is a conical or torsion spring, we will look for other ways to handle the springs.
“As customers are requiring higher feed rates in their assembly processes, we [are forced] to develop ways to not only wind the spring faster, but deliver the springs to the point of assembly more quickly,” says Given. “This is compounded when the springs also require testing of any kind.”
Bob Rice, team leader for applications engineering at Automation Tool Co. (ATC), says springs are a challenge for four basic reasons:
Springs are also difficult to work with because they are often small and easily damaged. They are typically bowl-fed, which can cause the springs to become tangled. This problem is usually common with springs that are tightly wound and contain open ends.