Custom Tube Bender Eliminates Cut-Off Waste of Tubular Parts for Exercise Machines


unique swing-away wiper die facilitates waste-free bending of short and complex tubular shapes



Asheville, NC – Unison has won an order for a custom-designed tube bending machine and special tooling from Cybex International, the leading manufacturer of premium physical exercise equipment. Incorporating a unique servo-driven wiper die mount, the machine 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.



Cybex produces a diverse array of physical exercise machines at two large state-of-the-art manufacturing facilities in Medway, Massachusetts and Owatonna, Minnesota. Its unique machines are developed with the help of exercise science principles to be biomechanically correct and generate optimum results with minimum stress on the body.



Nearly all Cybex exercise equipment is based on high quality tubular steel framework, most of which is produced at the Owatonna plant. The framework 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, Cybex constructs frames from three different sizes of robust 11 gauge 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 to 10 feet and involve a diversity of bends – from shallow curves to tight bends with a centerline radius as small as 4.8 inches. Most parts require bend accuracies of plus/minus 1 degree or better, to help achieve end-to-end positional tolerances as tight as 0.03 inches. 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 of between 12 and 30 – 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 has to use overly long tubes and then cut them to length after bending. This has several drawbacks: it is time-consuming – it is much more difficult to cut a formed part than a straight tube – and demands additional processing and quality control stages. It also creates material scrap, which is expensive and at odds with the company’s commitment to environmentally responsible manufacturing practices.



The custom bending machine that Unison has designed will bend these complex and short tube shapes without generating cut-off waste. Instead of a stationary wiper die, Unison's 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-inch (100 mm) all-electric CNC tube bender from Unison’s Breeze range. It has also been 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 also 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 a Unison tube bender. Other factors include very favorable comments from machine operators at reference companies that Cybex 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.



As Jim Saynor, Unison’s Senior Commercial Manager, explains, “Most of our machines are used for bending tubes with round profiles. The Cybex application is unusual, involving a diversity of tube profiles, and the company has built up considerable expertise in this highly specialist discipline. We have worked closely with Cybex 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's specialist know-how is encapsulated in the design of the tools, machine and tube bending methodologies.”



About Unison

Unison started in business by developing control systems for metalworking machinery – supplying a number of prominent UK machine manufacturers in the 1970s and 1980s. In 1991 the company moved into machinery design, focusing on machines for tube bending. At that time, tube bending machines were powered hydraulically. In the early 1990s Unison invented a range of machines employing electrical servo-motors for controlling bending motion. These were the world’s first 'all-electric' machines for tube bending. The performance of Unison's new machine design – with its fast and repeatable software-controlled set-up, right-first-time action, low power consumption, and quiet and clean operation – was an instant success. The company has progressively led the tube bending machinery industry by increasing the tubing diameters that can be formed using all-electric motion and is now one of the world’s leading manufacturers of tube bending machines and associated software. In 2014, Unison took another quantum leap in power by developing a servomotor-powered machine architecture that is capable of bending thick-walled piping with diameters of 225 mm and more. www.unisonltd.com



About Cybex

Cybex International produces premium commercial fitness equipment designed to deliver unparalleled results for exercisers from first-time users to professional athletes. The company’s dedication to exercise science, through the Cybex Institute, leads the fitness industry in providing scientific basis for the development of exercise machines that enhance human performance. With over 90 patents, Cybex equipment is innovative in design, durable in structure and engineered to be biomechanically correct to produce optimum results with minimum stress on the body. The company is a US manufacturer with two state-of-the-art manufacturing facilities in the USA and a workforce of 560 employees. Cybex commercial products are sold domestically primarily through the Cybex direct sales force with light commercial and consumer products going through specialty fitness dealers. Internationally, Cybex products are sold through distributors in over 90 countries across the globe. www.cybexintl.com



For more information about Unison, please contact Dale Coates at:



Unison Ltd., 28 Schenck Parkway, Suite 200, Asheville, NC 28803, USA. t: +1 (828) 771 0850; www.unisonltd.com

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