When you’re spending up to 300 hours of machining time converting a 10-ton Inconnel inlayed billet into a multi-faceted valve block weighing just 5.5 tons after a multitude of boring, drilling, facing, tapping and threading operations to tolerances of 0.025 mm, you need to be confident that the machine being used can be trusted to work unmanned to consistently produce such workpieces.
'Producing such high-value and often very complex components is our marque, and we know we can trust our new Hyundai-Wia KBN-135 CNC horizontal boring and milling centre,' says Robert Cunningham, General Manager of Bridgeforth Engineering.
'Supplied by T W Ward CNC Machinery (Ward CNC) the machine was installed because we needed extra capacity to meet a growing order book for the supply of a range of components, as well as supporting project management services, to our range of blue chip customers primarily in the oil and gas market. The company is currently working 24/7 to keep up with demand.
'We already have two horizontal boring and milling machines, but these are ageing and we needed to invest in the most cost-effective and highest technology mill-bore centre we could find to ensure our machining routines remained efficient and effective. We actually looked at about five different machines and their specifications were very similar. But Ward CNC offered the most cost-competitive package with a machine of high quality and robust construction – which is exactly what we needed.'
Located in Fife, near Edinburgh, the family-run, privately-owned precision machinist (which also has a sister manufacturing site in Kunshan, near Shanghai, China) also based its machine choice on its past experience with Ward CNC-supplied machines – a Toshiba BMC-50 and a pair of Hyundai-Wia KH63G machining centres, 'which we found good value for money,' adds Mr Cunningham – as well as the back-up and support that has been provided by the Sheffield-based machine tool specialist.
From its modern, purpose–built headquarters, Bridgeforth boasts a full range of CNC and manual machining capabilities including horizontal machining centre work up to 630 mm2, milling to 3,200 mm by 11,250 mm by 1,600 mm, turning up to 1,400 mm diameter and, with the new Hyundai-Wia, boring and milling within X, Y and Z axes travels of 3,000 mm by 2,000 mm by 1,600 mm, respectively, plus a W (spindle) axis travel of 700 mm. The impressive machine portfolio is complemented by co-ordinate measuring, laser marking and non-destructive testing.
The company also offers a comprehensive project management service where it works with specialist ‘partners’ to provide single-source turnkey solutions embracing, for instance, welded fabrications and surface treatments.
'We started investing in really large-capacity machines a few years ago to differentiate ourselves, continues Mr Cunningham. 'There are plenty of companies able to machine parts up to a ‘manageable size’ for the oil and gas sector, which represents about 95 per cent of our business.
'But we needed to stand out from the crowd and invest in the appropriate machine tools to go that much further and produce large and heavy prismatic and shaft-type workpieces, most of which are machined in very small batches of usually three-/four-off and invariably as one-off prototypes (such as the valve block that the KBN-135 is used for). And we needed to be able to produce such components consistently and cost-effectively, hence the investment in the Hyundai-Wia.'
Bridgeforth’s new travelling table-type KBN-135 offers a generous 2,000 mm by 1,800 mm rotary B axis table that can accommodate loads of 10,000 kgs, coupled with a standard 40-tool automatic toolchanger (primarily Sandvik tooling is in use at Bridgeforth). Tools up to 130 mm diameter by 600 mm long and weighing up to 20 kgs can be carried; however, tools up to 250 mm diameter can be used by leaving adjacent pockets empty
With a 135 mm spindle diameter and ISO 50 taper, 22/18.5 kW spindle motor, the machine has a maximum spindle speed of 2,000 revs/min in four ranges (drive to the spindle is via a four-step geared head enabling full advantage to be taken of the high torque developed) and rapid traverse rates in X, Y and Z are 8,000 mm/min.
The machine features closed-loop linear scales in X, Y and Z as well as a high accuracy rotary encoder for the B axis table – the B axis table can rotate at up to 0.8 revs/min and has 0.001° indexing. For 90º direct indexing, a shot pin is engaged to maximise stability under cut, especially when utilising the machine’s drilling or milling off-centre capabilities. Spindle cooling is part of the standard specification.
Maximum rigidity for stable machining is derived from the single structure main bed which is complemented with six supports under the saddle. To ensure optimum rigidity when the spindle quill is extended up to its 700 mm maximum stroke, it is clamped once positioned in the W axis.
The specification, adds Mr Cunningham, 'provides Bridgeforth with a capability to meet every foreseeable demand for bore-mill workpieces'. And, he continues, the machine was up and running after less than a day’s training: operators from an existing bore-mill centre with Fanuc CNC (15M system) were simply transferred to the Hyundai-Wia where the Fanuc 32M CNC accepted the compatible machining programs.
Since its establishment in 1979, Bridgeforth has striven to ‘get it right, first time and on time, every time’, a philosophy that depends as much on the workforce’s engineering excellence as it does on high-tech machining. With 53 employees, the company continues to look to the future, not only in terms of modern machines but also in ensuring that its bedrock of engineering expertise is maintained. So, an ongoing apprentice programme sees three new apprentices taken on each year for long-term (four-year) apprenticeships – the first year at a local training school and the remaining time spent in the factory plus one day each week at college. 'If we hadn’t taken on apprentices some time ago we wouldn’t be in business today,' Mr Cunningham concludes.