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Couplings Synchronize Motion in Pipe Bending System

Pines Technology’s (Westlake, OH) Model 250 Heavy Duty CNC bender is a powerful automatic precision system for fast, repeatable bending of tube and pipe up to 10" in diameter. Providing fast setup and changeover advantages, this giant bender has an advanced level of programming to deliver automated high performance and flexibility in tube and pipe bending operations.

The giant bender depends on a reliable automated system for loading, aligning, and clamping so that the 10"- diameter pipe is bent precisely and consistently. Motion in this automated loading system is provided by a servo motor and drive combination that utilizes CD® couplings from Zero-Max (Plymouth, MN) to synchronize and balance motion. Because these benders are designed for many years of operation with little or no maintenance, every component, especially the couplings, is key to the system’s reliability and longevity.

The design challenge for the loader system of this size was to come up with a method that would ensure smooth, synchronous motion. The design configuration had to be simple enough to allow for disassembly after initial testing in Pines’ manufacturing plant, then reassembled for actual operation in the customer’s overseas production facilities.

While the actual pipe bending operation is hydraulically powered, the loading system is driven by an electrically powered Yaskawa servomotor and Stober gearbox with a reduction rate of 69.43:1. With a travel distance of 76", this loading system pushes, aligns, and clamps tube weighing up to 1.5 tons as it progresses through the bending cycle.

To handle this motion, a set of four tip-up arms in the loader isolates a single tube from the load rack and deposits it on feed rolls located at the end of each traverse arm. The four traverse arms move the tube into position for the bending machine carriage to grasp the tube. These four traverse arms must move simultaneously to transport the heavy tube to its desired position for bending.

Pines design engineers determined the best way to achieve this motion was by using a single servomotor connected to a gearbox. The load position varies with the tube OD and bend radius so the servomotor, with help from the CD couplings, is used to precisely position the traverse arms. Floating shaft CD couplings connect and span the distance from the gearbox to the traverse arms, and engage with a pinion gear that engages the racks on the traverse mechanisms. Actual maximum shaft speed of the traverse mechanism is 70 rpm for a maximum linear speed of 880 inches a minute. The maximum motor/gearbox torque is 907 lb/in of continuous torque.

The floating shaft CD coupling is a zero backlash and torsionally stiff spacer coupling. It dampens backlash and shock without the coupling fatiguing with an open arm disc design made of composite disc material. This design absorbs and cushions misalignment forces and backlash that may occur from the servomotor’s intermittent motion. Also, the CD coupling provides support for the floating shaft component with very little radial load on the connected equipment and bearings.

Each loader uses one CD Double Flex coupling and three CD Floating Shaft Double Flex couplings of various lengths. For assembly, after initial alignment and anchoring of the loader components, the floating shaft couplings are bolted in place to join the loader segments. Then the motor/gearbox assembly is installed with the final attachments made to the CD coupling. At this point, the loader is test operated manually to verify that there is no binding or undue loading on the couplings.

This article was contributed by Zero-Max, Plymouth, MN. For more information, visit http://info.hotims.com/45606-321.