The installation by Newburgh Engineering of a horizontal machining centre with integrated facing head is forecast to not only slash machining times for oil and gas valve components by at least 30% but also create a step-change in the machining philosophies that have historically surrounded these safety-critical parts.

The Rotherham-based precision machinist had traditionally produced the components in stages on ‘standard’ vertical turning machines and horizontal borers with head-changing capabilities. This process entailed relatively high levels of manual intervention for component unload/reload, as well as and head changing and resetting.

The components will now be produced complete in a single set-up on a Dörries Scharmann DBF 630 horizontal machining centre from Birmingham-based Starrag UK Ltd (www.starrag.com).

Crucially, this machine features an integrated facing head that allows all operations — boring, milling, drilling, tapping and turning — to be completed in a single set-up, thereby eliminating a major source of spindle down-time and potential repeatability problems in head resetting. In addition, the machine — which will be the first of its type in the UK — will eliminate the need for hand finishing on these components.

Newburgh’s managing director, David Greenan, said the new-generation DBF machine (specially designed by Dörries Scharmann for the single set-up machining of pump housings, fittings, sealing flanges and rock bits, as well as valve housings to accuracies of 5-6µm — particularly on bore finishes) will transform the company’s machining routines.

“Historically, they have involved high levels of operator skill and manual intervention, with all the incumbent problems that potentially creates in terms of machining concentricity. The result will be a one-hit, highly reliable and much more cost-effective process.”

On-going improvement

The continual search for improved process efficiency — plus effectiveness and reliability — is a Newburgh cornerstone that sits alongside its long-term manufacturing alliances. It has served the company well in the supply of large-capacity components to its Tier One and OEM partners in the aerospace, rail, defence, power generation and nuclear industries, as well as oil and gas customers (which account for 50% of its business).

“We’ve been producing this range of valve components that fit within a 750mm-cube machining envelope for some years. They start as closed-die forgings that are a mixture of carbon and duplex steels, Inconel and Super duplex, and are often nickel or alloy-clad. By definition, such materials create machining problems in both heavy rough machining and fine finishing — especially when machining the ports and ring grooves.

“While our dedicated machining cells ensure that there is no compromise on delivery schedules and levels of work-in-progress, customers are reluctant to pay more for their components, so we have to continually seek ways to work ‘smarter’ and employ ‘state of the art’ processes that supersede standard CNC routines — and in this case, eliminate the ‘black art’ of resetting facing heads. Hence our investigations on these valve components.”

The search for an alternative and more productive method of machining fell largely on the shoulders of Newburgh’s operations direct-or Danny Gibbons and production engineer Andrew Wright, who is currently seconded to the Nuclear Advanced Manufacturing Research Centre (NAMRC), of which Newburgh is a member.

On the shortlist

Included among the NAMRC’s machine tool portfolio is an HEC 1800 from Starrag Group member Heckert, and it was the performance and robustness of this machine that put the Dörries Scharmann DBF 630 onto Newburgh’s short-list. Contact was then made with Starrag UK’s Birmingham office.

Mr Greenan says: “With its solid construction, the DBF 630 certainly has the rigidity we are looking for. We wanted to continue taking heavy cuts up to 5mm deep, but at higher feed rates than we had previously been able to apply before the finishing cuts, which are to open tolerances of generally 0.06mm. That said, the DBF 630 is perfectly capable of producing
micron finishes.

“While the machine offered the required machining performance, what stood out in particular was the overwhelming advantages of the built-in facing head, as this means we can complete a number of tasks in a single setting. It’s a technology that Dörries Scharmann has over 20 years’ experience with; it also means we can use automatic tool changing, as well as features such as high-pressure coolant and on-machine probing.”

With a 35kW 1,700Nm-torque spindle, twin pallets (630 x 630mm) and a 1,000 x 870 x 1,200mm work envelope, the DBF 630 comfortably accommodates Newburgh’s valve components. The machine also has a 3,500rev/min milling and drilling capability, and it is rated at 500-1,200rev/min for turning. There is also ±35mm U-axis traverse for radial adjustment of the turning tooling, and control is via a Siemens Sinumerik CNC system.

Newburgh sent sample parts to Dörries Scharmann for a series of process and time studies to prove that the machine could consistently produce the parts — and achieve surface finishes to the 0.8µm CLA required to eliminate the need for hand finishing. The application of ceramic tooling was also investigated with dramatic results, cutting one machining operation from 2hr to 2min (the fact that the DBF 630 is totally enclosed aids the use of ceramic tooling).

Newburgh also contacted existing DBF users, to ascertain their views on the machine’s performance and reliability. Newburgh’s DBF is scheduled for delivery in September, prior to which the machine will be the subject of exhaustive commissioning trials to ensure it will be up and running very soon after it arrives. It is the first Starrag Group machine that Newburgh has purchased; Matthew Jewitt.

Newburgh’s sales director, says he can not wait for the machine to be in place: “While the DBF 630 will bring immense efficiency gains on existing parts, there is no reason why other similar complex work can’t be considered for it, too. Our investment in new-generation machines allows us to stay ahead of the competition. It offers a capability that will be fully promoted when the company attends this year’s Offshore Europe show in Aberdeen in September.