Custom-made bundle unloader handles extremely cambered tubes

Situation

Every automated process requires consistent parts to run efficiently and continuously. Out-of-print parts at the input end of a process generally lead to defective parts at the output end, and in extreme cases, they bring the process to a halt. In tube fabrication—especially of long, thin tubes, such as those used for automotive brake lines or fuel lines—noncompliance with straightness specifications is a common issue. Using a bundle unloader for such tubes is difficult, and in some cases impossible, because of the challenges in untangling a single tube. Singulating one tube and removing it from the bundle introduces unpredictable movements in the bundle that invariably tangle other tubes. The dynamic and unpredictable characteristics of this process makes it difficult to automate.

For low-volume applications of this sort, most fabricators rely on manual unloading. However, when an automotive parts supplier encountered this situation, it needed an automated process to keep up with the contracted part volume.

The parts came from a draw bench and were loaded into a hopper and sent to a straightener. Some camber was expected, but some of the tubes had up to 7 inches of camber from end to end.

Resolution

Engineers at Haven Mfg. found a way to use the tube shape as an advantage. They developed a system that uses several belts in parallel as a flexible trough. After a dozen or so tubes are deposited into this trough, the belts are drawn up slowly, making the trough wider and shallower, which causes the tubes to begin to untangle and settle into a single layer, unbundling themselves. A conveyor system moves the tubes through the machine as detectors monitor the contents of the conveyor. When the system detects more than one layer of tube—a tangle—the conveyor reverses direction, dumping the tubes back onto the belts, which have been relaxed to create the former trough. The cycle then starts over.

The tubes leave the sorting section in a consistent orientation, regardless of the camber’s severity, and the machine deposits them onto an inclined outfeed tray that acts as a buffer. A lifter then removes them, one tube at a time, and sends each one to the straightener.

Although the machine’s input section is not a fast-paced operation and includes frequent reversals, the buffer facilitates a continuous output that keeps pace with the straightener, which has a 7-second cycle time.

A video of the machine in action is available at http://havencut.com/custom-bundle-loader-severely-bent-tubes-video.

Haven Manufacturing Corp., http://havencut.com