Innovative Tube Equipment Corporation (Chicago, IL), the North American distributor for Unison Ltd. (Scarborough, UK), commissioned what is believed to be the largest all-electric tube bending machine ever produced at Newport News Shipbuilding (Newport News, VA), a division of Huntington Ingalls Industries that supplies nuclear-powered aircraft carriers and submarines to the U.S. Navy. The machine is capable of generating over 265,000 ft-lb (360,000 Nm) of torque that can bend piping up to 8 in NPS, with an outside diameter of 8.625 in or 219.1 mm, with Schedule 80 wall thicknesses of 0.5 in (12.7 mm).
For more than 128 years, Newport News Shipbuilding has designed, built, overhauled and repaired a wide variety of ships for the U.S. Navy and commercial customers. The shipyard is now the sole designer, builder and refueler of nuclear-powered U.S. Navy aircraft carriers, and one of only two providers of nuclear-powered U.S. Navy submarines. With vast facilities located on more than 550 acres along 2.5 miles of waterfront in Newport News, the shipyard employs more than 23,000 people, many of whom are third- or fourth-generation shipbuilders. The shipbuilder has more than seven years of experience using Unison all-electric tube benders that began back in 2007 when the yard took delivery of three machines to help fabricate tubing and piping systems for use on aircraft carrier projects.
Unison has progressively increased the tubing diameters that can be formed using all-electric motion, including a quantum leap in power developed in 2014 through a servomotor-powered machine architecture that is capable of bending thick-walled piping with diameters of 225 mm and more. Now, the availability of all-electric, servomotor-controlled bending machines for pipes of the size used at Newport News brings significant productivity benefits to the fabrication of a ship’s pipework when compared with conventional hydraulic powered machinery, including smart software-controlled set up and right-first-time precision bending with exceptional accuracy and repeatability. Bend precision is aided by the inclusion of a unique laser-based system that automatically measures and adjusts bend angles for spring-back of the pipe metal.
Unison also won an order for a custom-designed tube bending machine and special tooling from Cybex International, Inc. (Medway, MA), a leading manufacturer with a workforce of 560 employees that builds a diverse array of premium physical exercise machines at two large state-of-the-art manufacturing facilities in Medway and Owatonna, MN. With over 90 patents, Cybex commercial products are sold domestically, primarily through a direct sales force, with light commercial and consumer products going through specialty fitness dealers. Internationally, the equipment is sold through distributors in over 90 countries across the globe.
This unique exercise equipment is developed with the help of exercise science principles to be biomechanically correct and generate optimum results with minimum stress on the body. Incorporating a unique servo-driven wiper die mount, the custom tube bending machine from Unison has been specifically designed to enable Cybex to reduce waste material costs by eliminating the need to cut shorter tubular parts to length after bending.
Nearly all Cybex exercise equipment is based on high quality tubular steel framework, most of which is produced at the Owatonna plant, that is a highly visible part of the brand image and therefore needs to combine an aesthetic look and feel with structural strength. To achieve this, frames are constructed from three different sizes of robust 11 ga steel tubing, using a variety of proprietary tube profiles including flat-sided oval and compressed octagonal shapes. Producing smooth, wrinkle-free bends in these types of tubular profile is technically challenging and demands considerable expertise.
Cybex currently uses hydraulic tube benders to handle the bulk of its production needs, together with a single all-electric CNC machine for more complex parts that require multiple bends with different radii. The tube parts range in length from 2 ft to 10 ft and involve a diversity of bends, from shallow curves to tight bends with a centerline radius as small as 4.8 in. Most parts require bend accuracies of ±1 deg or better to help achieve end-to-end positional tolerances as tight as 0.03 in. After bending, the parts are welded, cleaned, shot blasted and powder coated. To ensure that the final product is unblemished, every stage of this process is subject to stringent quality control.
Parts with complex bend shapes are produced in small batch sizes – typically in lots of between 12 parts and 30 parts – on the company’s existing CNC bending machine. Like most rotary draw tube benders, this is fitted with a stationary wiper die to help control material flow and prevent tube collapse during tight radius bending. The permanent presence of the die imposes a limit on the minimum length of tube that can be bent. This means that to produce short parts, Cybex must use overly long tubes and then cut them to length after bending. This has several drawbacks: (1) cutting a formed part is time-consuming and much more difficult to cut than a straight tube; (2) a formed part demands additional processing and quality control stages; and (3) processing a formed part creates material scrap that is expensive and at odds with the company’s commitment to environmentally responsible manufacturing practices.
The custom bending machine from Unison will bend these complex and short tube shapes without generating cut-off waste. Instead of a stationary wiper die, the new machine uses a unique swing-away tool mount which, like all motorized axes on the machine, is driven by a software-controlled servomotor. Moving the wiper die away from the pressure die towards the end of the bend cycle allows the tube feed mechanism to be driven closer to the rotary bending head, facilitating fully automated production of short parts. The new machine is based on a 4 in (100 mm) all-electric CNC tube bender from the Breeze range of units. It is configured with multi-radius bending capability and multi-stack tooling to allow complex parts to be produced in a single, uninterrupted machine cycle. The precision of the new machine is aided by the inclusion of a unique laser-based system that automatically measures and adjusts bend angles to compensate for tube spring-back after bending.
Cybex cites fast and repeatable software-controlled set-up, bend accuracy and low power consumption as key reasons for its choice of this custom tube bender. Other factors include very favorable comments from machine operators at reference companies that were visited during its pre-order selection process, and Unison’s willingness to develop a custom tube bending machine specifically to help improve the flexibility and efficiency of manufacturing small parts. “Most of our machines are used for bending tubes with round profiles,” explains Jim Saynor, the senior commercial manager for Unison. “The Cybex application is unusual because it involves diverse tube profiles and they have built up considerable expertise in this highly specialist discipline. We have worked closely with them and our tool manufacturer to ensure that the machine we deliver will provide a right-first-time manufacturing solution, from the moment that it is installed. This collaboration included videoing existing bending operations to make sure that every iota of Cybex specialist know-how is encapsulated in the design of the tools, machine and tube bending methodologies.”
Unison, 28 Schenck Parkway, Suite 200, Asheville, NC 28803, 828-771 0850, www.unisonltd.com.
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