Multi-axis marvels

12 min read

Andrew Allcock reviews recent investment in machining centre technology. Multi-axis technology, including simultaneous cutting, is a central theme, he discovers [Extended version of magazine feature]

Ufone, a Black Country specialist in subcontract machining of large, heavy components, the UK's first DMF500 Linear 4/5-axis vertical machining centre with five-metre X-axis has been installed, supplied by DMK UK (01582 570661). Auto-indexing to incline the spindle head on the DMF machine is positional in 1° increments, but this fifth CNC axis cannot be interpolated with the other four. Ufone is the first in the UK with this machine The machine significantly extends the size of prismatic component that the Dudley-based precision machinist can produce, as the previous maximum was 3 m in X. Capable of producing parts weighing up to seven tonnes within a 5,000 by 1,100 by 900 mm working envelope, the DMF machining centre has a linear motor that accelerates the spindle head in the X-axis at 6 m/s2 to a rapid traverse speed of 80 m/min. Apart from allowing us to produce larger components, the DMF500 Linear is much faster than our 3-axis CNC travelling-table milling machines," reports Ufone's general manager, Gary Meusz. "Drilling multiple holes around a ring or flange takes half the time or less, while thread milling is similarly rapid, thanks to the HSK 100A spindle taper, whose rigidity also eliminates chatter, improving both surface finish and tool life." And the 23.5 kW/10,000 rpm spindle with 40 bar delivery of coolant or air through the centre is a huge step up from the company's 3,000 rpm spindle available on the CNC mills. "Using a solid carbide drill with through-coolant, hole production is three times faster than we were previously able to achieve," the general manager adds. "We are getting similar time savings on some milling operations when using the latest indexable-insert cutters. Moreover, with standard ball-nose mills, we consistently achieve a really good surface finish, which is difficult on our other plant. Other strengths of the machine cited are its automatic toolchanger - Ufone previously used manual toolchanging on its CNC mills; the 4th axis indexer with tailstock, which can accommodate components spanning the full length of the table; Heidenhain control – the setters are already familiar with this technology; HSK A100 spindle, as opposed to BT50, which provide the rigidity and precision necessary for machining features down to 20 microns total, as demonstrated during cutting trials; the ability to partition the table into two zones, each 2.5 metres in X; Renishaw probing, which automates measurement and program update for large parts that 'move' between operations. "Every week we are picking up a new customer, or else a customer we have not dealt with for many years, largely due to having this additional capacity. It is strengthening our order book and giving us an increasingly competitive edge as we come out of recession," concludes Matthew Wild, Ufone's managing director. WINNING MORE WORK Founded in 1982 as an aerospace fabrication company, 100-employee Supercraft is now a full-service manufacturer for machining and fabricating high precision aerospace components, adding treatments such as welding and painting, before building these parts into recognisable airframe assemblies. Operating from three sites in Byfleet, Surrey, Supercraft provides a total, make to print, manufacturing solution to the aerospace sector, and has recently installed three multi-axis machining centres from Yamazaki Mazak UK (01905 755755). By offering this total solution, and working as a partner to its customers, the company's turnover has grown over the past two to three years by around 30 per cent. Key to this growth has been the move to more modern, and versatile, machine tools, especially the multi-axis machines from Yamazaki Mazak. Mazak technology has underpinned Supercraft's growth "We bought our first Mazak about four years ago," says Paul Barber, Supercraft's sales director. "This was a Quick Turn Nexus 200 MY turning centre. The capabilities of this machine allowed us to be competitive on batches as low as one-off, thanks to the speed of set-up and the ease of programming on the shopfloor. It was the success of this machine that prompted us to investigate further investment into multi-axis machining centres." The company then installed 5-axis technology, so as to capture work its 3- and 4-axis machining centres could not economically tackle. Supercraft's first venture into five-axis machining was to purchase a Mazak Variaxis 630-5X II twin-pallet machining centre, this was quickly followed by a Variaxis 500-5X II twin pallet machine. "We manufacture some very complex parts," says Nigel Prior, Supercraft's manufacturing engineer. "With our previous machine capacity, these would take up to six set-ups to complete. With the Variaxis, we achieve this in two; and with the twin-pallet arrangement, we can run first and second operations back-to-back. This improved our service of supplying fast track deliveries to our aerospace customers." One example of productivity gains through use of the Variaxis machines is the manufacture of a series of rib bracket supports. Cycle times on these components has been reduced by 30 per cent, with the additional bonus of an improvement in the accuracy and quality of contoured features, leading to a reduction in the amount of supplementary hand finishing that is required. Installed during 2009, the Variaxis machines quickly became established and the advantages that they brought to Supercraft initiated the discussions about the next stage of the investment programme. The Variaxis machines have a workpiece capacity of 500 mm diameter by 400 mm (500-5X) and 730 mm diameter by 500 mm (630-5X), but Supercraft was receiving inquiries for work outside of these capacities. The result was an order for a Mazak VTC 800/30SR travelling-column vertical machining centre equipped with the optional rotary table, making it a full, simultaneous, 5-axis machining centre. This unit has a table size of 3500 by 820 mm and a machining capacity of 2000 mm X 500 mm, when using the five axis option, the VTC-800/30SR has given Supercraft the confidence to bid for and win new work. The versatility of the machine is enhanced by feed rates of 50 m/min and a 35 kW, 18,000 rpm spindle. COMPLEX REQUESTS Seven vertical machining centres from Hurco Europe (01494 442222) have been installed during the past 10 years in the Witney, Oxfordshire works of Acrona Engineering, including, most recently, a 5-axis VM10U with WinMax control purchased at the beginning of the year. Acrona Engineering's most recent Hurco acquisition has beena 5-axis machine, but this is just one of many Hurcos installed in recent years The investment was prompted by existing customers in the aerospace, medical and motor sport sectors, in particular, asking the subcontractor to manufacture more complex parts from a variety of materials. However, the machine's presence subsequently attracted additional work from new sources as well. One of the first jobs onto the machine was an aluminium component for equipment designed to secure screw-on caps to the tops of drinks bottles. Another application was one-hit 5-axis machining of cryogenic components from copper, involving positioning two of the CNC axes and interpolating the other three. In an example of fully interpolative 5-axis machining, Acrona Engineering produced clutches from titanium billets for an F1 race car. "We are winning more and more contracts from first-tier suppliers to the aerospace industry, which now accounts for about a quarter of our turnover," explains Albert Soave, owner and managing director. "Our plan is to move further into this type of high added value work, for which the 5-axis machine is ideal." REELING IN THE WORK For the past twenty years, ISO 9001-accredited Reeling Systems has been in the unusual situation of having a single customer for a niche product that founder and managing director Martin Campbell describes as a sophisticated version of the simple garden hose reel. Poor service from subcontractors led Reeling Systems to install machines from XYZ Machine Tools The Whitchurch, Hampshire-based company is a primary fire prevention equipment supplier to Chubb Fire Mechanical – which in turn is a primary contractor to the Ministry of Defence – and Reeling Systems' hose reeling systems can therefore be found on board every UK fighting vessel from surface ships to submarines. Initially assembling and supplying only the hose reels, Reeling Systems has progressed to providing all of Chubb's 30-plus MoD-related product families comprising some 300 part variations. Until last year, all machining work had been outsourced, but the volumes involved, typically up to 250-off, meant that, even in recession, no one subcontractor seemed willing to commit wholeheartedly to Reeling Systems, and late deliveries of finish machined components were becoming a problem. So the decision was taken to invest in a 20 hp, 8,000 rpm XYZ 1010 VMC vertical machining centre with fully-integrated 4th axis and a 38 hp, 3,500 rpm XYZ 250 TC turning centre with live tooling. The company then needed additional turning capacity and, with limited workshop floor space, opted for a 20 hp, 5,000 rpm XYZ Compact Turn 52 turning centre, all three machines are equipped with Siemens conversational CNC (XYZ, 01823 674200). The XYZ 1010 VMC's 4th axis capability can be used either as an indexer for moving the part to a set angle or as a fully-interpolated axis for spiral milling. Programming via the Siemens ShopMill CNC's Tracyl Cylindrical Transformation function is easy, requiring the operator simply to program a pattern of holes, profile or pocket flat and then letting the control wrap it round the cylinder, thereby removing the need for complicated maths or CADCAM. The 'JobShop Concept' of making programming as quick and easy as possible is also evident in the Siemens ShopTurn CNCs fitted to the XYZ 250 TC and XYZ Compact Turn 52, with numerous canned cycles built in to cater for commonly used functions such as grooving, threading and undercutting as well as drilling and tapping. "What we did last year, in effect, was to start another business, squeeze everything into our existing factory and, having gone through a rigorous re-organisation, to do it all over again with the installation of the third machine," says Mr Campbell. "So you can see that the decision to begin machining in-house, which meant taking on additional people, was not taken lightly. However, the choice of XYZ Machine Tools has proved to be a very fortunate one, not least because I was a complete novice as far as machine tools are concerned and I knew I would need a lot of advice and support." Mr Campbell and colleague Neil Stewart received three days' basic free-of-charge training on each of the three XYZ machines. They also benefited from the telephone assistance that comes as standard with each new CNC machine purchased, with no charge or expiry time limit for this service. "The on-line assistance has been very good in terms of addressing day-to-day issues," Mr Campbell confirms, "as a two minute 'phone call can prevent hours of wasted time." Reeling Systems also received additional free-of-charge on-site applications assistance, the objective being to reduce the initial learning curve to the absolute minimum. Unlike Neil Stewart, Martin Campbell had no prior experience of CNC programming, setting or methodology. However, he points out that "our on-site training went through everything, from starting the machine through to writing complete programs, an approach that is of vital importance to anyone lacking CNC experience, especially someone like me who has no knowledge of G and M codes. "On our first visit to XYZ's headquarter in Burlescombe, I could see that the intuitive level of the software made programming so much easier, added to which we could ask any questions and spend as much time as we needed to find out about any XYZ product. It was very much a case of 'How does spiral milling work? Well, we'll program this machine and show you'." Materials machined by Reeling Systems include stainless steel 316, phosphor bronze, gun metal (copper/tin/zinc alloy), naval brass (copper/zinc/nickel alloy), commercial brass and aluminium. HIGH SPEED VMC At 20-employee Greenway Pepper Precision Engineering, a subcontractor in Newcastle-under-Lyme, aluminium components are being machined much faster, following the installation of a Brother high speed, 4-axis, vertical machining centre (01926 852725) from Whitehouse Machine Tools. For example, a medical component that used to be produced in one hour and 10 minutes on a standard, one-year-old VMC now takes just 26 minutes to machine on the Brother. Overall, cycle times were more than halved for producing this and five other components transferred in the first month. Moreover, as the Brother machine is equipped with a twin pallet changer – Greenway Pepper's first – parts are presented more quickly to the spindle, so floor-to-floor times are reduced further. It is not surprising that Greg Pepper, joint owner and managing director, reports such dramatic improvements in productivity. The Brother TC-32BN QT has a top spindle speed of 16,000 rpm and 1.5 g acceleration to rapids of 70 m/min in X,Y and Z. These figures are much higher than the 8,000 rpm and 30 m/min on the subcontractor's other VMCs recently purchased from another supplier. Higher spindle speed and accelerations boost productivity for Greenway Pepper "It was the relative slowness of our other machines and a sudden upturn in medical business that prompted us to buy the Brother machine," says Mr Pepper. "I had seen the TC-32BN at MACH 2008 and visited the Whitehouse technical centre in Kenilworth last year, where I was impressed with the demonstrations. It was like having the output of two machines in the footprint of one. "However, the opportunity to invest did not materialise until work for an AIDS blood sampler and a DNA testing machine arrived in quick succession, pushing our company turnover past £1 million." Trials were carried out by a number of potential machine suppliers, including Whitehouse. The TC-32BN QT was at least a third quicker than the other shortlisted VMCs and 2.6 times faster than a twin-pallet model offered by a recent supplier to the Newcastle-under-Lyme factory. Installed in March 2010, the TC-32BN QT is operated flat-out by Greenway Pepper all of the time. High-pressure coolant at 70 bar through the spindle and tool dispels the large amounts of swarf generated. Coolant of a relatively thick consistency prevents tap breakage, which is important as a large amount of synchronous tapping is carried out at 8,000 rpm. This feature, a Brother first, involves true linear interpolation with spindle rotation, in Z, resulting in higher speed, better control over thread quality and depth, and longer tool life than with conventional rigid tapping. Workpiece clamping is configured differently on the two pallets, allowing Greenway Pepper a high degree of versatility. On one pallet there is a MicroLoc baseplate with clamping elements for workholding. The other pallet supports a Nikken trunnion-and-tailstock indexer that rotates a MicroLoc plate through 360 degrees to provide a 4th CNC axis. The medical component referred to earlier, whose cycle time has dropped from 70 to 26 minutes, is the side plate for a new instrument that will allow on-the-spot DNA profiling by medical staff and police forces. Due for global launch in July 2010, the US-designed equipment has an aluminium casing comprising a family of parts, prototypes for which Greenway Pepper produced at the end of 2009 in batches of 50-off on its slower machining centres. The subcontractor is looking forward to reaping the benefits of the 63 per cent saving in production time on the Brother machine once volume manufacture starts. To extract more benefit from investment in the twin-pallet machine, the company has moved from single- to double-shift operation, 7.00 am to 10.00 pm. "Securing the DNA machine contract took three months and underlines our evolution from a jobbing shop into a value-added machining facility, offering production of small to large batches and a fully integrated design, development and assembly function," Mr Pepper says. "The back-up provided by Whitehouse was very good in transferring this and other work to the Brother machine. It included writing early programs and comprehensive operator training both at Kenilworth and on our shop floor." No other beer in the world is linked to its bottle like Corona Extra. Yet, when people think of Corona, they don't think of a bottle. They think of where they would like to be – relaxing on a warm beach, gazing out at picturesque azure seas. Years of effective marketing have convinced people that Corona Extra is an expression of lifestyle, not just a bottle of beer. People all over the world heartily agree, and choose to drink a Corona because it brings to mind relaxation and escape. Think of Corona as a holiday in a bottle. DRINKS ALL ROUND The makers of Mexican beer Corona Extra, Grupo Modelo, is a machine shop populated with a number of Haas machine tools. The machine shop now has a total of five Haas machining centres – three VF-3s and two HS-1RPs. "We bought the Haas machines because of price, performance and service," says machine shop manager Julian Fernandez Rodriguez. "The president of the factory was very satisfied with the first Haas machine because the service was so good. So it was an easy decision to purchase other Haas machines." Bottle moulds for Corona, made by Grupo Modelo, Mexico, on Haas machines The moulds to create a Corona bottle are complex and include 10 different parts. One set of moulds creates the top and the neck of the bottle, while a second set forms the bottom half. "The top of the bottle and the mould that creates it are important for several reasons," explains Salvador Vazquez, assistant manager. "The rim of the bottle is where your mouth goes, so it has to be very smooth. Another reason is that the bottles require an opener – they're not twist-off – so the top has to be very strong." The different parts of the mould are made from cast iron and brass. The cast iron comes from foundries in Indiana. Manual mills are used for roughing the B96 cast iron, and then Haas machines are used for the precision milling, drilling and tapping. It takes about seven hours to create a complete mould for a Corona bottle, with finishing and polishing taking the most time. The Haas machining centres have helped the machine shop improve how well the two halves of a mould fit together. The shop uses a Haas VF-3 VMC to cut the grooves in the mould. "The different parts of the mould have to be machined to tight tolerances so that they fit together perfectly. We've had better repeatability and accuracy with the Haas machines," says Mr Rodriguez. The popularity of the Grupo Modelo brands keeps the factory running around the clock, and the machine shop knew it would need machines it could count on. "The service from Haas has continued to be outstanding," notes Mr Rodriguez. "We have to have the machines up and running to keep up with the demand. We can call Haas and they are here in 20 minutes. Haas provides far and away the best service when compared to the other CNC manufacturers." A mould is generally used to create 80,000 bottles before it has to be replaced because of heat and stress. The machine shop manufactures more than 600 moulds per month to keep up with the worldwide demand for Corona. In addition to making moulds for 12-ounce bottles, the shop also creates moulds for 10-ounce bottles and small 8-ounce bottles, appropriately named Coronitas. In addition to making moulds for beer bottles, the machine shop creates moulds for bottles of Tequila Sauza. The tequila bottle features an intricate label on the neck of the bottle. The Haas machining centres have helped reduce the time it takes to create the label. "We have seen an improvement in cycle times using the Haas machines, especially on engraving," Mr Rodriguez explains. The engraving of the cast iron was once done by hand and took four days. It now takes only 40 minutes, using a Haas VF-3 VMC with an HRT-210 rotary indexer." The machinists enjoy using the Haas machines because of the user-friendly control. "It was very easy to train employees how to use the Haas machines, because the control is so easy to use," says Mr Rodriguez. "We also like how the control is the same on the vertical and horizontal machining centres. Once you learn how to use the control, then you can use either type of machining centre." First published in Machinery, July 2010