A hole lotta love!

Is deep hole machining still considered a black art at the bottom of a black hole? Mike Richardson discovers how this niche application is experiencing increasing demand

from landing gear manufacturers looking for serious weight reduction.
You can't see anything because there's so much smoke and there's lots of loud noises that makes your head hurt. No, it's not a case of too much dry ice at a heavy metal rock concert! Welcome instead to the so called ‘black art' of deep hole machining - perhaps the most niche of all machining applications and one which requires slightly more hands-on involvement than simply pressing the green button, standing back and praying it will work! With costly materials being machined that in turn require increasingly expensive machine tool technologies, today's aerospace subcontractors need the uncertainty and unwanted production inefficiencies when proving out a deep hole machining process like the proverbial ‘hole in the head'. To their aid comes Sandvik Coromant, who officially opened its first deep hole machining (DHM) global application centre in Cirencester, Gloucestershire last May with the purpose of researching and developing new and innovative DHM techniques for customers from a range of industries. By packaging today's knowledge of DHM for tomorrow's needs, the centre serves as an interface for research institutes, machine tool manufacturers and universities to conduct tests on specific components. The DHM global application centre has a specialised deep hole drilling machine capable of internal profiling and chamber boring, a small turning centre for machining guide pads and measuring equipment for setting tools and checking component features. Data output from the deep hole drilling machine enables metalcutting processes to be recorded and analysed during operations, with copies of the data made available so that any future replications can be established against a benchmark. The establishment of the DHM application centre follows the acquisition by Sandvik of BTA Heller Drilling Systems, a supplier of deep hole drilling products, in 2009. With the company now consolidated within the organisation, Tony Evans, the former BTA Heller deep hole machining guru and now senior manager at Sandvik Coromant revealed during the launch that there is still a perception that deep hole drilling is a ‘black art'. So is Sandvik on a mission to demystify the process? “Our application centre at Cirencester has given us an opportunity to apply processes and analyse them in order to develop DHM methods where our customers can appreciate the sheer scale of them,” Evans begins. “The productivity gains and advantages that deep hole drilling offers many industries are substantial, so we're on a personal mission to make a difference. One of the big drivers in the aerospace industry centres on reducing the weight of aircraft components to make them more fuel-efficient. The knowledge transfer and the ability to do this from Cirencester gives us the opportunity to make that difference.” Deep and meaningful Sandvik reckons that there is a multi-million pound potential for aerospace-related deep hole machining work over the next few years. Understandably, many landing gear component manufacturers are falling over themselves in overcoming the technology hurdles to find even more weight reduction features, and whilst some parts only require typical centre lathe set-ups and traditional boring bars to remove surplus material, other lightweighting features require more complex operations that see specialised boring techniques going far deeper inside the component. “We've been running machining trials with a number of second tier landing gear subcontractors using our DHM processes rather than conventional ones,” Evans continues. “In one example, we've reduced the subcontractors' five-hour machining cycle time down to two hours on a landing gear link beam component. Although the subcontractor already had a deep hole boring machine, they assumed they would need to purchase a large and expensive CNC machining centre to perform machining trials. We've saved them lots of money - plus they can now machine parts cheaper too.” Evans says that to make the most appropriate use of the DHM application centre, the objective is to divide the time equally between R&D, training and customer project work: “Right now our focus is on internal training, because we need to grow our resources,” he explains. “Sandvik's approach has always been global in the sense of providing the same levels of expertise and service everywhere.” More than a feeling

Sandvik's global footprint, but with a local feel means that wherever customers are located, its global application centre in Cirencester is ready, willing and able to help them overcome the complexities of DHM. “The great thing about our application centre is that we can quickly demystify DHM simply by showing the customer exactly how the production process is performed,” he maintains. “And because of the way we've designed our deep hole drilling machine - and also the way it collects cutting data - we can show exactly what's going on between the tool and workpiece by using sophisticated cameras and sensors that monitor its every move to collect the data and output to a spreadsheet. On completion of machining trials, we can analyse torque loads and coolant flows, how the torque on the spindle can increase as the tool begins to wear - and how this affects swarf control and coolant flow.
“For example, there is a yield point when the swarf begins to come away from the surface very easily. We can demonstrate this happening by using data that shows the torque value before the yield point is reached and the torque value dropping off afterwards. This in turn enables higher feed rates to be used as the material begins to cut efficiently, as opposed to literally being rubbed away.” Amassing a wealth of empiric data to demonstrate the different ways that Sandvik can machine a raft of landing gear components with unique deep hole features, Evans reckons that two recent landing gear projects undertaken by Sandvik have yielded productivity gains of over 35% for its customers. “There's a huge sense of relief from customers that we now provide them with the ability to experience and prove out DHM processes using mock-ups within a relaxed training environment rather than a production one,” concludes Evans. “To my knowledge, Sandvik is the only company doing this. We can take these machining trials offline without affecting our customers' production - a particular benefit for those companies involved in prototype to product cycles. Our application centre offers a ‘hands-on' and almost multimedia-like experience for people to get up close and personal with the ‘black' part of the black art.” Or perhaps they've now seen the light. As your deep hole machining centre's boring tool disappears quietly inside the workpiece creating less smoke and loud noises, maybe it's less a case of ‘Smoke on the water' and more like the sweet sound of ‘Hole lotta love'? www.sandvik.coromant.com

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