Unison builds automated tube bending cell for UK metalworking contractor | Automation.com

Unison builds automated tube bending cell for UK metalworking contractor

*Bending/punching cell with robot handling facilitates unmanned 'lights out' production
*Embedded 'poke yoke' check ensures the cell cannot make a bad batch

Ilkley, UK, November 16, 2006 --- A fully-automated bending and punching cell developed by Unison has helped tubular metalworking contractor Olicana Products to dramatically increase its manufacturing capacity. The cell is programmed to fabricate bath stands for four of Europe's leading bathroom product manufacturers. It currently produces W-shaped tubular frames with up to six bends and fixing holes every 11 seconds.

The machinery cell replaced a manually operated production line, introducing a fully automated process that has allowed Olicana to increase capacity by adding an unmanned overnight shift. All that's required for production to continue is for the feed hopper to be filled before staff leave for the day. In the morning, up to 2000 finished parts are stacked and ready for shipment.

The cell consists of three major machines: a five-axis, all-electric 25 mm tube bender from Unison's Breeze family, a robot arm, and a punch press. The input hopper's 2000 tube lengths capacity is enough for more than six hours of continuous production.

Unison designed the cell to operate fully automatically, once the required fabrication program is selected and the hopper is stocked. A pneumatic cylinder mechanism built into Unison's tube feeder automatically centralises tubes as they are fed, making sure that any minor variations in length allowed for in the tolerances is divided equally between each leg of the finished W-shape frame. A servo motor driven arm feeds a tube into the bender, which then performs up to six compression bends depending on the program selected (three variations of bath stand are fabricated).

The machine has two electric servo motor driven bend heads, mounted on two servo driven carriages, plus a clamp and rotation unit in the centre of the machine for rotating the tubes. This arrangement allows the symmetric W shaped stands to be produced very rapidly by making two bends simultaneously. The articulated robot arm then unloads the part and transfers it to a press, which punches fixing holes. The robot then grips and hangs the finished part on a rail, ready for shipment.

The all-electric nature of the tube bending machine was an important selection factor for Olicana for two reasons. Three styles of bath frame are manufactured. Compared with a traditional hydraulic bending machine, the all-servo control of bending axes provided by Unison's Breeze machine means that set-up for a batch is completely automatic, requiring just the loading of a program. The operator does not need to manually set-up the tooling, or produce a trial part before production can begin. The second benefit is reduced energy usage, as power consumption drops almost to zero as soon as bending is finished. With an equivalent hydraulic bending machine, the oil pump typically remains operational - wasting a lot of electricity.

This savings in electricity costs was verified after the all-electric cell was installed, by measuring and comparing consumption on the all-electric tube bender against the power consumed by a hydraulic bender performing the same task. Unison's Breeze machine consumed approximately 10% of the power of a hydraulic bender during bending operations, as well as eliminating the energy wasted by the common practices of heating or cooling hydraulic oil (and/or leaving the machine on overnight) to maintain bending consistency.

"We like to develop long-term supply relationships with our clients, and as a result we are happy to invest in automation such as this dedicated cell, which gives both our customer and Olicana a lot of flexibility," says Rupert Pearson, Managing Director of Olicana Products. "We can now produce extremely high quantities to satisfy just-in-time orders if required - shortening lead-times and removing cost from the supply chain. The cell has also allowed us to increase output and make better use of our significant investments in capital equipment, without increasing either head count or factory size."

Olicana chose Unison to develop the cell because of its previous experience with the company. Olicana is one of the UK's leading tubular metalworking contractors, and has operated Unison all-electric bending machines on its manufacturing floor successfully for several years. Unison had also provided Olicana with valuable tooling and engineering support with tube bending which included help that extended the working life of an old hydraulic bender.

Olicana typically expects payback on major capital equipment purchases within two years, and the cost of the new cell will be amortised within this timeframe.

Unison designed and produced the cell in just 20 weeks. The hopper and tube bender are standard items in its product range. The company is also an approved system builder for Motoman robots, and selected and programmed one of the 6-axis UP-6 Series arms for this application. All of the system integration was handled by Unison's engineering team in Scarborough, with a programming focus on making the finished system extremely simple to use. To keep the cell operating, all the operator needs to do is load the hopper with the right tube lengths, and select the bending program for the required shape from a Windows based menu.

As the cell operates automatically, without supervision, Olicana requested some kind of safeguard to ensure that a bad batch could not be manufactured - due to an inadvertent human error of loading the wrong program or the wrong tube length. Unison's engineering team employed the principle of 'poke yoke' (which is Japanese for inadvertent mistake proofing*) to guard against such a malfunction. The solution was provided in the form of sensors added into the punch press. The punch press loads the bent tube shape into one of three different positions according to the type of bath stand being fabricated. Photocells added into these positions detect if the tube length is incompatible, and the cell automatically raises an alarm and stops production at that point.

"Automated tube fabrication cells can significantly enhance both productivity and flexibility, as Olicana's application demonstrates," adds Unison's Alan Pickering. "Although this cell produces just three types of part in mid to high volumes, the repeatability of all-electric tube bending machines, combined with the programmability of the system, means that this type of automation is just as applicable to much of the small to medium sized batch production quantities that we often see in Europe."

Based in Ilkley, UK, Olicana Products offers a design and manufacturing service for mid to high volume tubular metal products, and has a particular reputation with high-end cosmetic bending applications, including designer office furniture. Production is carried out at its UK manufacturing facility, and via overseas partners.

*Poke yoke. Developed at Toyota by Shigeo Shingo, this principle (roughly translated as inadvertent mistake proofing), targets the design of processes that have built in checks or safeguards that make it difficult for an error to be made. By this means, any inadvertent mistake is caught close to the time it happens, before it can continue through the process and cause expensive rework or scrap at a later stage.
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