March 14, 2014
A typical bending machine process is feed-bend-feed-bend, or maybe feed-bend-feed- rotate-bend, until the feedstock is used up. However, this isn’t the end of the fabrication process, which includes a subsequent cutting step. The cut often means waste, especially for short-length parts, and the problem is compounded when the volume is high or the material is expensive. Read about how one bender manufacturer changed the process to feed-bend-separate-feed-rotate-bend-separate.
Throughout manufacturing, waste is synonymous with high costs. The costs are even higher when dealing with tubular workpieces because they take up more space than flat sheet metal and, therefore, cost more to transport and to store. The costs associated with waste are higher yet if the fabricating process produces large batches of short lengths of tubing. Often, after bending, every individual component is cut to the finished length, resulting in substantial waste.
Schwarze-Robitec has greatly reduced this cost driver by building a cutting tool into a bending machine. Bending and separating in one pass reduces waste by up to 90 percent, depending on the bending shape, according to the company.
High-quality materials have found their way into all areas of automotive production. Tubes are no exception: Manifold tubes in the engine compartment, axle components, and exhaust system components are manufactured from cost-intensive materials in vast quantities. Bending very short lengths to the right length can be tricky, and often is impossible. In many cases, the part is manufactured with additional straight lengths before and after the bend, known as span and supporting lengths. After bending, the additional lengths must be separated from the bent part in separate operations and they accumulate as waste.
“This practice drives up the manufacturing costs for a component,” said Schwarze-Robitec Managing Director Bert Zorn. In addition to reducing, and in some cases eliminating, waste, bending and cutting on one machine shortens production time.
The company took a direct approach to this problem by building a cutting process into its bending machine. The bend-separate-bend process handles long lengths, including entire commercial lengths.
After the machine bends the first part, the next station separates the finished component from the straight remainder. The machine transports the straight section forward and the process starts over. In each case, only a narrow shaving is created, which is removed immediately. The process doesn’t generate chips or any sort of debris.
“Only at the front and rear ends of the tube does waste occur that cannot be used, which is conveyed out of the machine,” said Hartmut Stöhr, who is also a managing director at Schwarze-Robitec. “With the integrated system, up to 90 percent of the tube waste incurred with other production solutions can be avoided.”
A typical waste reduction is from 4 inches per commercial length to 0.4 in., which can be a substantial savings in high-volume applications. This also alleviates the need for a separate cutting machine, which frees up floor space and reduces operating costs in the form of depreciation. At the same time it increases productivity by reducing the cycle time.
The innovation has been developed for the company’s all-electric CNC 100 E TB MR and CNC 80 E TB MR tube bending machines. The former model optimizes the system’s efficiency because it is often used for large-volume production processes with short tubes. Moreover, the machines demonstrate that the bend-separate-bend concept works with many options offered on modern CNC benders: a loosely mounted bend former, magazine feeder, multiradius bending, mandrel bending, and bend-in-bend clamp jaws.
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