Intelligent Bending

The Walsall Wheelbarrow Company Ltd. (Wednesfield, West Midlands, UK) is the only manufacturer of wheelbarrows in the United Kingdom and has been at the forefront of the industry for more than 60 years. They originated the first steel wheelbarrow and were also the first to offer a lifetime guarantee on the polypropylene wheel centers that they fit to all of their barrow products. Today they produce a wide range of barrows for diverse applications, including an innovative line of ‘barrow in a box’ products. All of their wheelbarrows are made in the UK and they are the only manufacturer of wheelbarrows that uses UK-only parts. Their plant in Wolverhampton is the most efficient wheelbarrow production line in Europe, using an extensively automated process.

The plant installed their first automated production cell from Unison, Ltd. (Scarborough, North Yorkshire, UK) in early 2012. Based on an all-electric twin-head bending machine and a robotic handler, this cell replaced two early-generation hydraulic tube benders and a hole punching station, streamlining operations by allowing multiple processes to be performed simultaneously. Capable of fabricating almost three parts a minute, the cell helped the company to increase production capacity from 1,500 to 1,800 frames per day while reducing scrap and operating costs. Later that year, Walsall launched their unique barrow in a box line of products that are supplied in flat-pack form so that customers can easily take their purchase home with them in the trunk of a car. The concept has taken the market by storm, proving so popular with retailers and customers that the company recently sought to further increase manufacturing capacity with another production line to keep up with demand.

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The plant installed their second custom-designed automated production cell from Unison to help meet this huge demand. This cell is part of a new production line that makes the frames for these wheelbarrows and fully automates all tube bending operations. Commissioned during the summer of 2015, it enabled the company to dramatically increase manufacturing throughput from 1,800 to 3,500 wheelbarrows per day. “Our first production cell was the catalyst for production expansion,” notes Jonathan Thacker, the operations director Walsall. “It enabled us to re-engineer our manufacturing operations for high volume production and free up skilled staff for future product development. The success of our barrow in a box range is due in no small part to the manufacturing flexibility that the cell introduced. Increasing demand meant that we needed to expand capacity even further, so in 2014 we invested in a six-robot press line for wheelbarrow pans, followed about six months later by this second Unison cell for frame manufacturing.”

The new production cell comprises a tube bundle loader, tube orientation station, intermediate dual-arm loader, bending machine and a 5-axis articulated robotic handler. All five stages are controlled by a central PC. The tube bender is based on a customized 30 mm (1.25 in) single-stack all-electric model from the Breeze range. It features a long, narrow neck and bend head that is specifically designed to facilitate precision fabrication of the tight wheel-end bend of wheelbarrow frames without causing the tube to collide with machine architecture during the process. Once the bundle loader’s hopper has been filled and the operating program has been selected, the production cell operates entirely automatically. The bundle loader feeds tubes individually to the tube orientation station, which detects the weld seam and rotates the tube to the optimum position for bending. The tube is then transferred to the bending machine by the intermediate loader and, after being bent to shape, is removed by the robotic handler and placed in a multiple rack storage scheme, ready for hole punching and powder coating.

This latest cell forms an integral part of a new production line that is primarily designed to manufacture frames for the barrow in a box products. However, the cell is programmable and can also be configured for a variety of tube bending tasks to help handle peak production of other products. Each barrow in a box frame comprises three separate parts (to facilitate compact packaging) and is fabricated from 30 mm diameter steel tubing in up to two-meter lengths. During a standard 8-hour shift, the cell is capable of producing around 1,000 complete frames.

Walsall has become a strong advocate of automation, believing that it is key to maintaining a competitive advantage. “The only other way that we could expand manufacturing capacity would be by importing ready-made parts, which is inflexible and raises quality control and scheduling issues,” adds Thacker. “We now operate the most efficient barrow production line in Europe. We have also almost eliminated hydraulic tube benders from our process, in favor of the all-electric technology that has multiple advantages, including better process consistency, higher throughput, much lower energy costs and reduced need for skilled operators. Our standard production capacity is now 2,800 barrows a day. We can easily increase this to 3,500 at times of peak demand simply through extended shift working.”

Because barrow in a box products are designed for easy assembly by customers, the frame parts need to be bent very accurately, with precision placement of the various bolt fixing holes. For this reason, the tubes are swaged prior to bending and the holes are punched afterwards on a separate machine. The cell’s tube orientation station ensures that frames are bent in such a manner that holes are never punched through tube weld seams. This also helps to ensure process consistency, because the seam affects the spring-back characteristics of the tube during bending. The weld seam detection system works by evaluating the magnetic flux density of the tube as it is rotated, which provides a reliable method of correctly orienting the tube prior to bending. A key advantage of this approach is that it is impervious to the prevailing light conditions that can affect the accuracy of automated vision systems.

In addition to the Unibend control software on the Breeze bender, Unison also supplied the powerful Opt2Sim tube bending simulator to help Walsall implement a right-first-time manufacturing strategy that eliminates scrap material and any chance of damaging parts or the bending machine by trialing bending programs before starting production. In the first six months of use, the shop successfully developed some 20 programs for bending tubular parts for a wide range of products. The simulation software uses a CAD (computer aided design) model of the bending machine to generate detailed video imagery. It offers collision detection facilities with user-adjustable parameters for real-world environmental factors, such as the distances between the tube centerline and the ceiling, floor and walls of the production area. It also has in-built artificial intelligence to reiterate bend cycles until a successful solution is found.

The Walsall Wheelbarrow Company Ltd., Units 10/12 Phoenix Road, Neachells Lane, Wednesfield, West Midlands WV11 3PX, UK, +44 (0) 1902 304002, [email protected], www.thewalsallwheelbarrow.co.uk.

Unison, Ltd., 28 Schenck Parkway, Suite 200, Asheville, NC 28803, 828-771-0850, [email protected], www.unisonltd.com.