Nov 13 2007
A radically new automated tube bending cell has been developed by Unison. It provides a complete end-to-end loading/end-forming/bending and vision inspection process in the footprint typically required for a standalone tube-bending machine. Called Uni-vercell, its novel, all-electric machine architecture centred on an articulated robot arm breaks new ground in terms of performance and compactness.
Priced to compete with standalone tube benders, Uni-vercell is expected to rewrite the economics of fabricating tubular components for high volume applications such as those associated with the automotive industry.
"We've developed automated cells in the past around our standard tube bending machines. With Uni-vercell, we designed the system from the ground up, replacing the machine's carriage with a standard robot arm," says Mike Lawson, Project Manager with Unison.
He adds: "This allows us to make the cell much more compact, and gives perfect accuracy and repeatability because the arm retains the part for the duration of the process, and every part is inspected. It eliminates a lot of hardware, and by exploiting the vertical space, we effectively pack three machines into the space of one."
Unison's first implementation of Uni-vercell is for fabricating tubular parts with diameters up to 16 mm, and sits in a footprint of just 4.5 square metres. The machine includes a tube loader, 6-axis robotic arm with a 6 kg payload, 2-stage end-former, a multi-stack mandrel-less tube bender, and vision system. The integrated vision system allows the cell to operate unmanned with 100% inspection of bend angles and end form shapes. The programmability of the system also makes it easy to integrate further functions such as product labelling, which can easily be fitted into the extensive free vertical space.
Unison is well known as the pioneer of 'all-electric', servomotor-controlled tube benders. These provide substantial set-up, repeatability and scrap reduction advantages compared with traditional hydraulic-powered machines, and have become the de facto choice for most new machine purchases for smaller tube diameters up to 150 mm. The same architectural principles are exploited in this new machine, which features a software-centric architecture that gives unprecedented control over tube part fabrication.
Two major innovations are at the heart of Uni-vercell. The first is the replacement of a tube bender's carriage with an articulated robotic arm. By adapting the arm with a simple collet for gripping and rotating the tubular part, the arm is able to hold and manipulate the part continuously from pick up, through end forming, tube bending and inspection stages, to final release. This eliminates the cost of the carriage and the large space required for the carriage bed, as well as numerous intervening reference points, jigs and handling equipment that might normally be required when building a cell from discrete components.
The second major innovation is the development of an all-electric end former, to provide software-controlled, two-stage end forming (flaring and compressing). Compared with conventional hydraulic end formers, this approach eliminates the pump and tubing - and the associated heat, noise, energy consumption and environmental issues.
Uni-vercell delivers remarkable performance. It can fabricate parts to an overall accuracy of 0.1 mm. Although the cell is optimised for repetitive volume applications, the flexibility of the robot arm allows it to be configured easily for batch production as well. Accuracy and repeatability are assured, because of the system's use of closed-loop electronic control. The drift-free performance offered also means that the machine can be instantly set up to fabricate parts just by loading a program, rather than making and scrapping trial parts until the configuration is right.
The new cell is designed for continuous use and can easily fabricate thousands of parts a day. With a typical energy consumption of around 1.5 kW (measured using an example part with three bends and one end form, including stacking at the end of the process, and 100% inspection,) daily electricity running costs are around 7 Euros.
The software-controlled nature of the machine delivers many further technical advantages, including much greater control over the bending process. Fine adjustments to torque levels or movement profiles can be made, for example, to optimise bend quality. Complicated shapes that might be difficult to make on a conventional hydraulic machine can also be produced easily, because the machine is able to make intervening adjustments or moves between stages, to avoid a collision for instance. This programmability can equally be exploited to optimise cycle time - by making only the minimum movements required.
Programming the cell for an application can be achieved very rapidly thanks to Unison's powerful front-end software package, Unibend, and the friendly teaching software supplied with the robot. Programming bends and end forms requires only the input of data such as position, angle, rotation and torque, and the machine sets up automatically. All of the intervening movements required by the robot may then be programmed by simply positioning the arm manually and capturing the data. Using these simple techniques, a complete cell program can easily be produced in less than an hour. The fabrication processes and movement-related operations are also discrete stages of a cell program, allowing modifications such as fine tuning of bending or end forming, or movement optimisation to be made quickly, and without generating a new program.
Energy saving is a further major advantage of Unison's new cell, as it only consumes a significant amount of electricity during the actual bending and forming operations. No hydraulic system needs to be maintained at pressure, for either the bending or end forming tools. Typical energy consumption rate for a continuously processing cell is around 1.5 kW per hour.