North-Eastern sub-contractor chooses OSAI standard

Harkers Engineering of Stockton-on-Tees (www.harkers.co.uk) has the distinction of machining more heavy-duty industrial gas-turbine casings than any other company in the world and is a major sub-contract producer of large machined parts for the aerospace, oil and gas and power generating industries.

Massive investment over many years has taken the company from strength to strength and, in 1998, the family-owned business celebrated 120 years of trading.

So when it comes to upgrading and retrofitting many of its huge CNC machines, Managing Director, Malcolm Harker, has very strong views about which controllers the company needs to keep quality up and costs down.

The photograph shows an Osai controller in use on a Webster & Bennett boring mill.

"We initially chose 8600 Osai (Allen-Bradley) controllers on the strength of the fact that Rolls Royce and British Aerospace had standardised on them," says Mr. Harker, "and we were able to write customised routines with help from their operation at Poole. We recognised the trend towards PC-based controllers and the advantages they offer in being operator-friendly.

"We have now used Osai controllers for all retrofits for about 10 years," he says. "More recently we have gone for the Osai 10-Series with its big screen and its integrated PC, which is very similar in use and gives good visibility in the shop. The integrated industrial PC means that the power of the PC is available at the machine. Before, we had to purchase separate, additional PC's for each machine."

"Very simply, they have been the most capable and versatile controls available to cover a wide range of machines and have given us a commonality of control, so that operators can easily move from one machine to another," he adds.

Osai controllers are fitted to vertical and horizontal machining centres from Mandelli, Rambaudi and Wadkin as well as three vertical boring mills from Scheiss and seven from Webster and Bennett.

The Scheiss vertical boring mills range from 3-5 metres, the Webster and Bennett machines from 1.25-3.5 metres. The Wadkin machines are vertical spindle types and the Mandelli is a travelling column horizontal machine. The biggest and most complex machines fitted with Osai controllers are two Rambaudi twin-Sspindle gantry-type machines. In fact, 15, out of a total of 30 machines at the Harkers Engineering factory feature Osai CNC controllers.

Collectively, the vertical and horizontal machining centres cover capacities from 1.4 to 6 metres and will support set-ups with maximum weights of 2 to 40 tonnes. There is a also a range of CNC turning machines with diameter capacity from 600 mm to 7 metres and also able to accommodate work-pieces up to 40 tonnes.

Altogether the facilities enable Harkers to undertake machining on any medium to large component of any form, including those requiring three-dimensional operations. Some of the items are of very large diameter and of very tough materials such as tool steel, titanium and nickel alloys. Turning operations on such workpieces may involve speeds as low as 0.5 rpm and take up to 300 hours to complete a single operation.

"We are working to very fine tolerances," says Mr. Harker, " and need powerful editing and customising facilities within the controller because of variations in the materials with which we're working. Everything that can vary, does - hardness, distortion, stock allowances and so on. It takes a great deal of operator skill to achieve the tolerances that are needed for the aerospace and power industries. The 86000 and 10-Series controllers allow on machine editing and, now, we are introducing trigger probing which will need adaptive control."

The Osai 8600 and its successor, the10-Series numerical control system, provide state-of-the-art control with unbeatable flexibility, making them ideal for a wide range of metal cutting machines.

The standard controller covers applications from 3-axis mono-process up to the simultaneous management of 24 processes and 32 axes - all in a single CNC.

The management of such a high number of processes by a single CNC significantly simplifies many of the problems associated with multiple control integration in complex applications incorporating several machining heads.

Based on standard PC architecture, with Windows compatibility, the 10-Series is designed to provide easy commissioning and programming. A powerful DLL library allows the development of personalised graphics and shop management data-systems for tailor-made ease of set-up and user-friendly operation.

State-of-the-art computer technology, combined with sophisticated control algorithms, ensures superb results, particularly where a high quality of finish is required. This is achieved by a block execution time in the order of 1msec and an axis sampling time of just 200 microseconds.

The dynamic RAM memory, which can be extended up to 32 Mbyte can store all of the data and programs necessary for the control of 24 simultaneous processes. In excess of 400 Mbytes of part-programming storage is available with full DNC capability via RS232, a facility fully utilised at Harkers Engineering. NicSoft and Unigraphics are used, with GraphCAM providing part programming.

Harker's investment programme now includes up-grades of machines previously retrofitted with Osai controllers. A typical example is a Wadkin vertical-machining centre, upgraded from three to five axis control to accommodate the control of a tilting, rotating table. This was accomplished using the existing 8600 Osai controller. Retrofits and maintenance are performed by HI-TEC Machine Services - see www.hi-tecmachines.co.uk

Harkers Engineering's biggest market is power generation at about 60% of turnover, with oil and gas and aerospace (including space), taking up the majority of other work. Some two-thirds of their production is for export markets, for which the company has been recognised in Queens Awards for Export and quality and engineering excellence are assured under the ISO 9000 standards.

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