Complex, precise production

Stockport-based sub-contractor CTL Engineering claims a 50-year history in the manufacture of a wide range of parts in varying materials and weighing up to 10 tonnes. Its customer base takes in companies in the oil and gas, power generation and aerospace sectors. The company has recently installed two Yamazaki Mazak Integrex e-650H-II horizontal mill-turn turning centres, which are now fulfilling a contract for the supply of landing gear components for a military aircraft project. The machines have a turning capacity of 920 mm diameter and a 3 m machining length. "The Integrex machines have taken us into an area of manufacturing that our existing capacity didn't allow for," explains Ian Booth, managing director, CTL Engineering. "While we already had a large capacity machining capability, it was based around horizontal machining centres and vertical turning lathes. The added flexibility of the Integrex machines is allowing us to quote for work that would previously have been uneconomical for us, due to the complexity of components requiring multiple set-ups. Now, with the capability to machine components in a single set-up, we are proving to be highly competitive." Mr Booth explains that it wasn't plain sailing straight off, however. "We bought our first Integrex about three years ago and, to be honest, we struggled at first, because the difference in technology from conventional CNC machining to machining components in one hit is quite a leap, not least in terms of appreciating what these machines are capable of. Colleagues doubted that this was the right technology for us, but I was confident that this technology would set us apart from the competition." Once the first Integrex had been installed, CTL began discussions with a major customer in the aerospace/defence sector and this generated an order for the first operation machining of raw forgings for undercarriage parts for the military aircraft project. The major advantage of the e-650H-II for these particular components is that it can toolchange boring bars over 1 m in length, which is ideal for a component with a requirement to drill, from solid, a hole 130 mm diameter by 1 m depth. This hole is then bored and flat-bottomed. "The new cycle time for this component is one that we would not have believed possible," confirms Mr Booth. "We also have excellent process security and reliability, and the machine is handling the whole process very nicely. What we saw as a really critical operation is now quite simple." Image: CTL is also involved in manufacturing parts for somewhat older aircraft, like this WWII Spitfire, but still using its most modern manufacturing technology, of course As a result of this success, the customer requested that CTL investigate the possibility of taking on the second machining operation, which was being completed in-house at that time. To ensure capacity and continuity of production, this required the purchase of a second Integrex machine. "The second operation requires the finish turning of the hardened component, something that the new Integrex is handling with ease," the managing director says. According to Craig Booth, sales director, CTL Engineering: "The addition of the Integrex e-650H-II machines has opened up the opportunity to look at areas of manufacturing that we were previously excluded from. Although we are competing for work against other companies with similar capacity, we have the benefit of our experience across a much wider range of manufacturing sectors and of working in different materials that others may not have." CTL is finding innovative ways to make use of the e-650H-II units, offers managing director Mr Booth. "For example, we have just been awarded the contract by a customer based in Cirencester that specialises in the restoration of Rolls-Royce Merlin engines. As part of their work, they have to replace or renew the propellers and hubs, which previously involved a high level of manual finishing. We are now in discussions with Yamazaki Mazak to evaluate how these components can be fully machined on the Mazak Integrex machines." The successful application of the two Integrex multi-tasking machine tools has now prompted the purchase of a third Mazak. "The performance, quality and repeatability of the two Integrex machine tools opened a lot of eyes, both here and at our customers," Mr Booth underlines. "This, in turn, gave us the confidence to purchase a third Mazak machine, this time an 800 mm twin-pallet, horizontal machining centre equipped with a D'Andrea U-180 contouring head – the first such Mazak machine in the UK to be so equipped, in fact. "The HCN 8800-II will create additional capacity, and allow CTL to approach new and existing customers to quote for work that would otherwise have been beyond our capabilities," the managing director explains. "We had a certain amount of work for it before it was installed, but the residual capacity, when combined with the two Integrex machines, is now providing added flexibility to our production scheduling, a situation that will be a bonus to both CTL and its customers." PRECISION PROMPT A demand for increased precision of an existing component type was the challenge at toolmaker/sub-contract machinist Constant Precision. The introduction of a new, higher performance paper folding machine by a long-time customer presented a new challenge. Bedford-based Constant's proven milling-based method of producing blades and anvils, used in the printing industry for automatically creasing and folding paper and card, could not cope with the higher tolerances required for the high speed machine, nor the projected increase in production output to meet the order demands of its print finishing specialist customer. Constant undertook a study of possible methods of manufacture with several machine tool suppliers. In the mix also was sub-contracting the finish production of the blade and anvil – however, when possible suppliers looked at the number of variables in the component dimensions that could cause them headaches, they either priced the job right out of court or immediately declined to quote. But it was C Dugard's application team at Hove that suggested a switch from milling to grinding – Constant Precision was already a Dugard customer – and trials on a 3-axis CNC Chevalier Smart B-1224-II surface grinding machine demonstrated that the new method more than halved the original processing time for the two families of parts required, as well as ensuring the high level of quality demanded. Image: A change from milling to grinding at Constant was suggested by and successfully implemented with C Dugard The eight types of matching blade and anvil vary from between 350 mm and 500 mm long, and each is 12 mm wide and 40 mm thick. Batch quantities can often run to 200 pairs a month. Running down the centre of each blade is a raised triangular section just 1 mm wide, with a critical 0.1 mm radius at the top. Each side of the triangular section has to blend into either a large radius over the 12 mm width or a flat face, according to the material to be folded. The anvil has a 1 mm wide slot with a 0.1 mm radius running down its length that has to marry up to, and provide a datum for, the blade and material to be creased and folded. Both radii are critical, with tolerances having to be held within 0.03 mm, while the overall straightness of the grooves and triangular section has to be within 0.05 mm to prevent scratching, marking and out-of-position folding of the material factors that would lead to immediate rejection by the customers of both printer and finisher. After several discussions with C Dugard, an initial single fixture was devised for the Chevalier machine to produce one part at a time which, once proven, led to a double fixture that would enable two blades or anvils to be ground simultaneously using a paired grinding wheel. Key to the three-axis CNC grinding machine process was the multi-function programmable control that has variable graphic simulation for grinding and wheel dressing cycles. This allows the speed of the review sequences to be varied in both forward or reverse by the operator, using the machine's electronic handwheels. Preset dressing cycles can also be initiated at any time during the grinding cycle without resetting. This level of flexibility was important to managing director Charlie Constant as, depending on his customer's requirements to cater for unusual or different papers, inks and finishes, the profiles may have to vary slightly – and these can be accommodated with quick and simple adjustment of the program. Today, with the process developed and in production, the cycle time for each blade and anvil has been reduced by almost 60 per cent. Still working with C Dugard, Mr Constant is developing wheels and improving dressing cycles and their frequency, making full use of the flexibility of the machine's CNC to further improve the process. Returning to mill-turning, but this time for smaller components, and two Star CNC sliding-head lathes operated by Reading-based sub-contract machinist Rodmatic are able to mill-turn components of medium to high complexity as quickly as any of the 42 cam-type, six-spindle automatics on site, according to owner and managing director Brian Steatham. He also points out that the turned finish achieved using the Stars, mainly on stainless steel and steel components, is so good that subsequent grinding is frequently eliminated, lowering unit production cost significantly. BETTER THAN FIXED-HEAD, TOO And the Star sliding-head machines also outperform fixed-head machines, as he further explains, saying that, for smaller size, high accuracy mill-turned parts in lower volumes, a sliding-head lathe is twice as fast as an 'equivalent' fixed-head lathe – ie, one with a counter-spindle and two turrets having driven tooling. Equipped with a 4 m bar magazine and high pressure coolant to allow long periods of unattended running, the first Star was a 9-axis SV-32 of 32 mm bar capacity, installed mid 2007. It was followed in 2008 by a similarly equipped 7-axis SR-20RIII for mill-turning parts up to 20 mm diameter. They joined three multi-axis CNC fixed-head lathes for producing larger components. Image: Star sliding-heads are outperforming fixed-head machines at sub-contractor Rodmatic During machining trials against competitive sliding-head lathes, the Star machines were inherently faster. In addition, Mr Steatham felt that their extra weight and rigidity would allow the production of more accurate components. Rodmatic considers Star GB's service to be good and is comfortable dealing with the supplier's staff, both aspects regarded as important issues. Returning to the productivity gains of the machines, a multi-spindle auto takes around two days to reset, so batch sizes above 30,000-off are needed to justify the time investment. In contrast, sliding-head lathes can be set in a couple of hours, so much smaller runs are economic. Rodmatic has produced batches as low as 7-off on the Star machines, although runs can be as high as 5,000-off. When producing larger batches on CNC sliding-head lathes, Rodmatic uses form tools alongside single-point cutting tools to reduce cycle times, using its experience of wire-eroding and grinding of form tools for use on multis and transferring the technology to sliding-head machines. Dramatic reductions in cycle times are achieved, typically of around 30 per cent. For example, one component regularly produced, a profile-turned and bored steel shaft for a European customer in the fluid power sector, is machined in part by form tools in an overall cycle of 37 seconds. This is over 38 per cent faster than the 60 seconds it used to take by exclusively single-point cutting. The competitive advantage this gives Rodmatic has resulted in considerable business success at a time when many sub-contractors are struggling, it is claimed. Whereas order intake for the multis was down by 20 per cent during the last quarter of 2008, the sliding-head lathes continued to work flat out during that period, 24 hours a day, underlines Mr Steatham. Article first published in Machinery, May, 2009