Since its formation in 1970, Eldim BV, has grown to become a “trusted partner” of aero engine OEMs, supplying turbine components directly to blue chip names such as Snecma, Pratt & Witney, GE and Rolls-Royce on a ‘single source’ basis. Around 30 per cent of the world’s engine programmes now feature mechanical seals manufactured by Eldim.

Today Eldim employs around 400 people, a high percentage of whom are skilled technical process engineers and quality engineers. The company supplies turbine components to all of the world’s major aero engine programmes, exporting to countries that include Germany, the UK, France, Spain, Italy, the US and Japan. Since 2000 Eldim has been part of the global Sulzer Group, which employs around 10,000 people.

One of the principle reasons behind the company’s success in recent years has been the manufacturing strategy that Eldim deploys. This entails dedicating production cells to specific product types, such as blades, vanes, mechanical seals, inserts and fuel nozzle guides, so that continuous, high quality component supply can be guaranteed.

With so many turbine components manufactured from hard materials such as Hastelloy, Inconel and cobalt chrome, a favourite manufacturing technology for Eldim is electro-discharge machining (EDM). Using EDM, the tool (electrode) does not come into contact with the material being cut (unlike conventional metal cutting processes such as milling and grinding) so there is no adhesion of the workpiece to the tool.

EDM has been the preferred manufacturing process since the company’s inception and today Eldim has over 50 EDM machines on site, mostly arranged in cells. When demand dictates, certain cells require expansion, as was the case towards the end of last year when Eldim could foresee a forthcoming rise in quantities for mechanical seals.

Mechanical turbine seals are critical aerospace parts. They comprise a backing material that can be a sheet metal ring or a casting, on to which a honeycomb structure is attached to form the seal between the turbine and the blade tip.

“Accuracy is vital,” explains Eldim’s sales manager Sandor Delescen. “The higher the accuracy the better the customer can control the gap between the blade tip and the turbine, which has a direct relationship with the efficiency of the engine and thus reduce fuel consumption. In today’s competitive air travel environment, fuel efficiency is paramount. It is also important from an environmental perspective, which has been a key industry driver for the past 15 years.”

To meet climbing demand, Eldim needed to increase the number of EDM machines in the cell which produced the mechanical seals. However, because of the specific accuracy of the parts and the high speed of production, only advanced machines would be considered.

“After careful evaluation we decided to invest in three Sodick AQ55L die sink EDMs with linear drives,” says production leader John Gorree. “The influencing factor was the Z-axis cutting speed of 36m/min, which was our primary requirement due to the number of small vertical slots on our mechanical seals. Also, we had been using Sodick machines for the past five years and we trust the technology. Sodick machines are very reliable, which is crucial in a 24-hour production cell environment where the machines form part of a sequence of operations and are required to meet strict throughput targets.”

Forming part of a 12-process production sequence, the AQ55L machines at Eldim are complemented by an extensive range of manufacturing technologies, including milling, turning, grinding, laser welding, laser cutting, electro-chemical drilling and high temperature vacuum brazing.

The AQ55L claims to be the world’s fastest cavity sinking EDM for workpieces up to 1000kg. Thanks to its linear motor technology, high positioning speeds can be achieved across X, Y and Z axes. The AQ55L also features machining without flushing and a power saving generator.

“We wanted these die sink EDMs for production work,” adds Mr Gorree. “They would be required to work hard and provide real added value. Therefore we were looking for machines which were not only fast, but models with quick tank filling time, rapid toolchange and quick submerge times. We are always pushing our suppliers to focus more on production and I have to say that Sodick has done very well in this respect, moving their technology to the next level.”

Installed in December 2006 at the company’s site in Lomm, eastern Holland near the German border, the three AQ55L machines have been located in a production cell with other specialist machine tools to offer a single-piece flow line for the manufacture of mechanical aero engine seals. Each EDM machine in the cell performs a different operation, such as the generation of honeycomb surface features, ring segments and seal slots, on a total of eight different mechanical seal components that pass through the cell.

In total the cell produces around 1500 components a week in line with a predetermined ‘takt time’ – the pace of production required to meet customer demand. (Takt is a German term meaning cycle, rhythm or repetition time – Toyota used the word extensively in its Toyota Production System, the forerunner to Lean Manufacturing). Typical batch sizes are in the realm of 20-off, so rapid machine changeover is vital in order to keep lead-times short.

Because of the high accuracy levels required by the mechanical seals, general EDM tolerances on these parts are in the region of ±0.02mm, which are matched by strict, pre-defined surface finish requirements. To this end the machines are subject to regular parameter checks that conform to NADCAP – the National Aerospace and Defence Contractors Accreditation Programme.

“We take good care of our machines,” says Mr Gorree. “The front-line maintenance training provided by Sodick means we can maintain them correctly in-house, to minimise any possibility of downtime. However, past experience tells us that in the rare event of encountering a difficulty, Sodick is very quick to diagnose and solve problems.”

“Because we supply our customers on a single-source basis we have around 100 audit days a year,” adds Mr Delescen. “It is our quality procedures that set us apart from our competitors. We have quality engineers assigned to each production cell – it is a facet of our operation that represents around 20 per cent of our costs. However, our quality programmes and extensive aerospace accreditations, including ISO9002, AS9100 and various OEM qualifications are also our best defence against new competition. Gaining approval is a lengthy and demanding exercise.”

Aside from aerospace parts, Eldim also manufactures industrial gas turbine parts components for customers such as GE Energy, Siemens Power Generation and Alstom Power. However, although the two business streams may sound alike, Mr Delescen says the components are distinctive in their differences.

“While it is true that aero engine turbines and industrial gas turbines both have rotating blades, shafts, vanes and seals, aerospace turbines run extremely hot and have to be very lightweight, whereas gas turbines are more robust and heavy duty.”

Whether the parts are for aero engine turbines or industrial gas turbines, having the backing of a global enterprise such as Sulzer allows Eldim to adopt aggressive investment programmes.

“Investment is vital to the success of our business,” concludes Mr Delescen. “Machines such as the three AQ55L EDMs are around 10 per cent faster than our existing models, so that helps us drive down costs. Although we are a single source supplier we are not in a total niche where we can impose high prices. The current air travel market is being driven by cheap air fares and we have to fit in with that philosophy to prevent our customers going elsewhere.”

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