Novel twin-head tube/bar bender provides platform for high throughput automated production
PUBLISHED: 13 Apr 12
Unison's all-electric twin-head tube bending machine provides an ideal platform for high throughput manufacturing automation
Unison is demonstrating the integration flexibility and productivity advantages of all-electric twin-head tube and solid bar bending machines at MACH 2012.
These types of bending machines are popular with manufacturers producing tubular parts that have a high degree of symmetry because they can form two bends simultaneously, increasing manufacturing productivity significantly. Many applications can be found in industry including the production of parts for supermarket trolleys, wheelbarrows, furniture, and automotive components such as seat sub-frames and head rests.
Despite their popularity, twin-head bending machines are only produced by a handful of manufacturers, and most are large hydraulically-powered systems. Unison takes a different design approach: its twin-head bending machines have an 'all-electric' architecture, with all motion axes controlled by servomotors. The standard machine configuration comprises two separate bending heads supported on independent ballscrew driven linear carriages. A fifth axis controls a compact and fast actuating tube 'centre grip and rotate' unit, which can be mounted in a fixed position between the two heads, or removed from the machine. The flexibility of this design facilitates production of either 2-D or 3-D parts, and accommodates both symmetrical and asymmetrical parts.
The servomotor-driven centre grip and rotate unit is exceptionally compact and designed specifically to combine ease and speed of loading/unloading with a highly secure grip. It has an extremely narrow profile, allowing very close approach of the two bending heads.
"It's very easy to realise much higher efficiency and throughput of bending operations with Unison's particular style of all-electric twin-head machines," says Jim Saynor, Sales Manager of Unison. "They provide the documented energy saving benefits of our 'all-electric' architecture, as well as the auto setup feature of our other machines, requiring minimal operator involvement for 'right first time' manufacturing. Our twin-head machines are also designed to have low maintenance requirements - they utilise high efficiency ballscrew and linear bearing systems, servomotors, belts and gearboxes. The product is available for standalone operation using manual feeding and unloading, or it can be integrated with various levels of ancillary automation, including auto load and unload work cells for fully 'lights out' manufacturing."
The throughput advantages of twin-head bending are best realised with automated loading and unloading, so Unison has optimized the physical layout of its machine to simplify integration with tube in-feed and robotic arm or conveyorised unloading systems. Other automated functions can include rotating for weld seam detection, punching, washing and drying, and tube marking.
Compared to hydraulically-powered bending machines, the all-electric architecture of Unison's twin-head benders provides users with major cost-saving advantages. In addition to easier functional integration, faster setup and more readily achievable bending consistency, the machines use considerably less energy. Significant power is only consumed during the bending operations, whereas hydraulic benders normally require the oil pump to maintain a pressure reserve, wasting energy. Tests conducted by Unison show that during bending operations, a twin-head all-electric machine only uses about 10 percent of the electricity needed by a comparable hydraulic bending machine. Further energy savings are also realised, because it is standard practice to heat or cool hydraulic oil to ensure bending consistency.
The throughput of a twin-head bending machine depends on numerous factors, such as tube on-load and off-load times, the number, angle and plane of bends required, and tube material and size. However, an impression of machine capability can be gained from a recent application, involving production of cargo racks for vehicles. Using a custom setup that can process two tubes simultaneously, this Unison twin-head machine produces two parts from 25 mm mild steel tubing - each with four in-plane bends - every 14 seconds. This is achieved with a standalone machine configuration, using manual loading and unloading.
Unison has also recently supplied a twin-head tube bender, as part of an automated production cell, for manufacturing wheelbarrow frames. The cell handles tube loading, weld seam detection, all-electric hole punching, bending and robotic offload. Tight functional integration means that the bending machine is working continuously, maximising throughput - while one frame is being bent, another is being punched. Typically, each frame involves five in-plane bends and one out-of-plane bend; this customer is producing one complete frame every 30 seconds.
A video showing a Unison twin-head bending machine in an automated production cell for wheelbarrow frames can be viewed at: http://youtu.be/h1k52rG3tvM
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