Case Study Form follows function for press brake toolmaker Rolla-V
Most engineering companies forming thin sheet metal material rely on the capabilities of a CNC press brake. A UK-based manufacturer and supplier of press brake tooling, Rolla-V, has recently enhanced its production capability with the installation of an Excetek V400G CNC wire EDM machine.
Shortly after Kevin Marklew established his Halesowen, West Midlands-based precision engineering company, which focuses on producing high-quality press brake tooling, he had the opportunity to purchase the patent for the company’s now world-renowned Rolla-V tools. As he recalls: “A British inventor had designed the basis of the press brake tools operation, but we had to develop it so that it functioned correctly. Initially, this was a slow process because the machine shop was busy making tools for customers around the world using Amada, Trumpf, Bystronic, Safan, LVD Adira, Durma and Bakal press brakes. We made a sample tool at the start of 1994. Back then, there was a bit of a development going on where the channel tunnel was being built.”
There is a sad backstory concerning Marklew's involvement. He remembers the challenge behind this project: “People were being injured or killed jumping out of trains and landing on the sharp edges of the side rail fabrications. The rail project director needed a round cap on the box section, which there was miles of. The company originally contracted to supply it had failed to deliver. The sample tool I had at the time was only small, but I knew if I made it bigger I could produce it in one hit. They didn’t believe it could be done, but I made a tool that produced the semi-circular cap required and the business grew even further.”
As the reputation of the ability of the Rolla-V press brake tooling spread through the various industry sectors, the demand for it grew. The company developed it as part of its standard tooling range, so it is available in 500, 1,000 and 2,000 mm length runs, which can be ganged together to form longer parts.
Rolla-V had to increase its production capability and speed to be able to keep up with the orders: “The workload on the shop floor to deliver the quantity of orders we were receiving was taking its toll,” explains Kevin Marklew. “We invested in a Mazak CNC machine, a grinder and most recently also in electrical discharge machining equipment, namely the Excetek wire-cutting EDM machine, to refine the product and make it better.”
With 17 highly skilled and experienced staff working flat-out to meet production demands, the new wire eroder had to fit straight in. And it did, as Kevin Marklew remembers: “To efficiently create the different length Rolla-V tooling sections, we produce full length components, assemble them as a finished tool and then cut across the tool at required length. We had been doing this on a bandsaw. However, the finish was nowhere near the level we would want to present to customers, so various manually intensive finishing operations had to be applied.”
Wire erosion supplies the finish that was required
The cutting of the tooling sections, therefore, was a complex and particularly costly manufacturing step. Looking for a process that would reduce the finishing operations, Rolla-V decided for electric discharge machining and ended up investing in a wire EDM machine by Excetek.
Consequently, the long press brake tools are today simply cut into the correct sectional length using the Excetek V400G CNC wire EDM machine. Providing comparative performance levels to Swiss and Japanese wire EDM machines, the Excetek V400G reportedly offers a major cost saving against any equivalent-size machine tool. It has X and Y travels of 400 mm and 350 mm, respectively, and can accommodate large workpieces of up to 750 x 550 x 215 mm weighing up to 500 kg within a very compact footprint.
Like all the standard range of Excetek wire EDM machines, the V400G features a C-frame structure designed using FEA software to provide exceptional accuracy in the linear axes movements and to minimise any thermal influence. This is achieved with a honeycomb frame structure for rigidity and thermal stability.
Also developed by Excetek, the automatic wire feed and threading system is produced in-house. Designed to provide continuous unmanned operation around the clock, the feed and threading system offers the ability to thread the wire at the point of the breakage. An automated annealing system straightens the wire so that it can be threaded at the break point during machining with almost 100 percent reliability and without the need to return to the start position. Submerged wire threading is possible, which removes the need to drain and refill the tank. A water jet assist system is available for automatic wire feeds on tall workpieces.
The machine also features Excetek’s latest corrosion-free, electro-discharge generator technology, which improves cutting performance. While the cutting speed of every wire EDM machine is limited by the laws of physics and set by the thickness of the raw material being cut, it is a manufacturer’s corner control that defines its machine accuracy. Excetek’s software is said to ensure the motion control and spark generator work together for the optimum power ramping and compensation dwell on corners, avoiding wire twist and reducing corner ‘washout’.
Delivering tools on time with machines running around the clock
Rolla-V press brake tooling’s patented technology allows the receiving part of the tool to rotate about a predetermined axis so the tool moves with the sheet material. There are numerous advantages of using Rolla-V tooling. These include a much more tightly formed bend radius, typically half the radius achieved with conventional tooling, minimal material deformation, which improves fatigue strength and allows bends to be formed much closer to any holes or other features without distortion. Also, as the rotation of the tool does not ‘drag’ the sheet material across its surface like a conventional forming process, it means uncoated materials can be used without risk of marking.
“That final point is also important for material cross-contamination,” states Kevin Marklew. “Customers don’t like using the same conventional tools on stainless steel as they do on ferrous steel or aluminium. This is because the tool can ‘pick up’ from one material and particles can be deposited in the next sheet,” he explains.
Today, the wire EDM machine Excetek V400G runs almost around the clock at Rolla-V. Thus, the company ensures that its customers get their press brake tools on time. The goal is to enable them to quickly take full advantage of the benefits of the technology and functionality press brake tools contain.