Multi-axis marvels - machining centres in action

5 min read

One-hit machining via 5-axis machining at two companies is bringing massive rewards, while medical implant machining is benefiting from a low-cost 5-axis approach. Andrew Allcock explains

Since 2006, under the new ownership of ex-Wall Street investment banker Allan Edwards, Weymouth manufacturing company FGP Precision Engineering has evolved into one of the UK's leading machined parts subcontractors, serving primes and Tier 1 suppliers in the aerospace industry. Before Mr Edwards bought the company, FGP shareholder and director Nigel Pitman, together with senior charge-hand Simon Griffiths-Hughes, had already concluded the firm's 3-axis machining centres should be replaced with 5-axis equipment. The rationale was two-fold. First, it was to expand production into components requiring fully interpolative metalcutting in five axes, as such parts are normally of high added value. Second, to cut the number of separate operations required for less complex work. Following thorough investigation, DMG/Mori Seiki technology (0844 800 7650) was selected, with the first to arrive a 500 by 450 by 400 mm capacity DMU 50 eVo linear – there are now three of these, plus a larger (750 by 600 by 520 mm) DMU 70 eVo linear. All have an 18,000 rpm SK40 spindle, which best suits aluminium machining - the norm at the Weymouth factory. However, steels and titanium are also regularly processed. FASTER PACE In July 2012, an 8,000 ft2 extension on the Weymouth site was completed and, following this and cutting trials at DMG/Mori Seiki in Germany, an automated HSC 55 linear 5-axis production cell was installed. This features a nominal half-metre-cube capacity, 28,000 rpm HSK-A63 spindle, feed rates up to 80 m/min, plus a PH130 70-position automated storage and retrieval system for pallets, configured as a stack of rotary magazines on five levels holding Erowa pallets and fixtures. Says Mr Edward of the benefits: "As a rule of thumb, every time we install a new, stand-alone DMG/Mori Seiki 5-axis machine, we are getting parts off in one or two hits, compared with five to 10 operations when we use 3-axis CNC mills. Set-ups are faster, there is less risk of introducing inaccuracies and lead times are reduced. "We were expecting a further increase in output with our latest high speed cutting machine, compared with a 5-axis machining centre loaded by hand, and are pleased at just how much more productive the automated cell is. "Using the HSC machining centre with its faster spindle speed, higher feed rates and automated pallet handling, we have been able to cut lead times by a further 50%, resulting in startling increases in productivity," he states. Automation also allows a mixed schedule of components to be produced lights-out overnight during the week and at weekends, without operator intervention. Batch size can be from one-off to high volume, while repeat work allows maximum advantage to be taken of the advanced production planning available with the automated cell. Concludes Mr Edwards: "I would fill our machine shop with similar production cells right now, if I had the funds. High metalcutting speeds, top accuracy, good surface finish, reduced set-up times and less labour is a powerful combination, and it is definitely the way we will be focusing over the coming years. "Our customers like this approach, too, and are keen to see modern plant on the shopfloor – it gives them confidence. I believe it is the main reason that our order book is increasing." At Spromak, which makes products for the oil, gas and petrochemical industries, both onshore and offshore, a Mazak Integrex e-800 VII (01905 755755) has cut production movement of very large flanges and branch fittings. "Whenever we want to look at reducing machining time and production movement, we meet with Mazak," says Paul Sproson, managing director at Spromak. Indeed, the Huyton on Merseyside, North West of England-based company now has a tally of 14 Mazak machines and has been a Mazak user since 1982. Spromak's flanges and branch fittings are made from a range of materials, including carbon steel, stainless steel, duplex steels and high alloys such as like Inconel 625 and titanium. HEAVY PARTS PROBLEMS As Spromak's range of reinforced branch fittings and flanged fittings, known as O'lets, has gradually increased in size, production movement at its Huyton factory has become a growing problem. For example, an insert branch outlet could weigh as much as 142 kg and require a series of machining operations, including turning, milling and boring. "Increasingly, we had to move larger and heavier product across two or three machines, which was impacting on our machining times," Mr Sproson explains. "We wanted to be able to bring the product off completely finished, with all turning, milling and boring operations done." The company turned to Mazak, again. "With our products, you can't just buy a machine and set it to work straight away. We work with Mazak and our CAM software manufacturers to identify the optimum machining solution. After a lot of hard work, we identified the Integrex e-800V." The machine is a 5-axis multi-tasking machine with a pallet size of 500 by 500 mm and a powerful, high accuracy main table that can turn large diameter workpieces, with a rapid traverse rate up to 50 m/min. The machine has a maximum workpiece diameter of 730 mm and a workpiece height of 1,000 mm. "We are using the new machine on some very large workpieces, with a maximum outside diameter of 730 mm and a height of 980 mm," Mr Sproson highlights. "We have machined individual workpieces weighing as much as 0.5 tonnes." And the result is that Spromak has cut cycle times by 6-8 hours, with an average 50% saving, although 60-75% is not uncommon. "This has, in large part, been due to the reduction in production movement now that we are able to complete all operations on the one machine." And Spromak's latest acquisition is an Integrex i-400S, which the company hopes will have a similar effect on cycle times as did the e-800V, for a different set of products. Tecomet, in Wilmington, Massachusetts, USA, is a manufacturing and medical technology firm with a 40-year history of supplying some big-name customers. In 2010, the company set up a new machining operation at Wilmington, with this centred around a line of seven Haas DT-1 drill/tap machines, fitted with Haas TR160Y 2-axis tables (01603 760539). They were subsequently put to work on a new titanium spinal implant manufacturing venture. Tecomet manufacturing engineer John Kaminski is responsible for the new set-up. IDENTICAL SET-UPS "All of the machines are set up in the same manner," he explains. "We have a Haas 5-axis table on one side and a vice on the other side to do secondary ops. This arrangement allows the operator to have throughput of the product, without having a major set-up from one part to the next. All the programs get punched into the machine, and the tooling is already in the carousel, so going from one product to another is a very simple change. It's as simple as calling up the program and then pushing the button. That's it, you're up and running. Even if a customer calls us and says, 'I need a particular part right away,' I can transition on the fly, and just tell the operator to call in the program and get those parts out to the customer. It works out very well for us. "We also don't need to have an operator in front of every machine. It's an easy group to manage, so there's one guy running the seven – and we have two more machines on order," he confirms. According to Mr Kaminski, the biggest challenge in manufacturing the parts is the need to blend complex surface geometry – machined with multiple tools, approached from several attitudes. He explains further: "It's crucial to have the parts come off the machine with minimal bench work required to achieve the desired surface finish. We use a combination of 3+2 axes positioning and 4+1 axis simultaneous machining to produce these parts. The Haas machines, as we currently have them configured, are very accurate. The operators in many cases have machined entire batches of parts with minimal offsetting required." First published in Machinery, January 2013