• OEMs / Suppliers   Laserbeams keep control

Laserbeams keep control

Quality is of the utmost importance to the aerospace industry. Small wonder then that leading engine manufacturers like MTU Aero Engines use a laser controlled optical measuring system on over 100 machines. The process stability which the laser system offers is helping to achieve the best possible manufacturing results.
When your car develops engine problems, you simply pull over and wait for a mechanic. But when jet engines fail in an aircraft, the lives of several hundred people are potentially at risk. That is why we at MTU attach the highest priority to quality. All our components must satisfy the close tolerances which we specify – often to within just a few hundredths of a millimetre,” explains Walter Strohmeir, user support representative for NC engineering with MTU Aero Engines in Munich. In addition to supporting machine operators with virtually every aspect of NC machining, his responsibilities include the programming of CNC routines and procuring machines and the peripherals to go with them.

To fully meet the exacting production engineering demands of aero engine manufacture, the machining centres of MTU rely on non-contact laser measuring systems supplied by Blum-Novotest, for whose operability Walter Strohmeir is also responsible. In simplest terms, LaserControl NT is an optical measuring system for tool setting and tool monitoring.

The system with the most know-how

As well as providing basic tool breakage control, LaserControl NT systems capture data such as tool length, radius, wear, cutting edge bursts and spindle and tool carrier accuracy at nominal spindle speed. The systems also compensate for spindle displacement at high speed, and can detect and correct tool clamping errors.

“Way back in the mid Nineties, LaserControl NT won out against strong competitors in the selection process at MTU Aero Engines as being the system with the most know-how. MTU subsequently purchased the first laser system, and its existing machines were gradually up-graded, while new machines were acquired with LaserControl NT already installed,” says Daniel Czujek from the Technical Sales Department of Blum-Novotest and MTU support engineer. Today, MTU Aero Engines in Munich has over 100 Blum laser systems in use across the company. Around 300 to 350 MTU employees work with LaserControl NT in three-shift operation. A number of machines are also equipped with contact touch probes supplied by Blum.

In terms of quality assurance, the Blum systems make a major contribution to the manufacture of all MTU engines. They include the new GP7000 family of aero engines which the Mu-nich firm produces together with industry partners, with MTU taking responsibility for the low-pressure turbine, the intermediate turbine casing and the high-pressure turbine components. The GP7000 family of aero engines is used in the long-haul sector, including scheduled ser-vices of the Airbus A380 since August 2008. In its class, this jet engine is a benchmark in terms of reliability, fuel consumption and noise emissions.

A major role in aero engine manufacture is played by so-called ‘blisk machining’. Blisks – the term is a blend of the words ‘blade’ and ‘disk’ – marry maximum performance to minimum weight. The process involves integral rotor construction in which disk and blade form a one-piece component, rendering blade roots and disk grooves superfluous. “The chief advantages of blisks are their substantial weight saving, increased service life, decrease in the number of components through higher stage loading, and the reduction in the amount of maintenance that is required.

Most parts are made from titanium. For tool setting and monitoring we deploy LaserControl NT throughout the entire blisk production line,” explains Heinz Baumgartner, blisk production team leader for the medium-pressure compressor for the TP400 engine programme. He supervises virtually all of the machining operations that are involved in ‘blisking’. Almost half of his team of 19 work with the Blum systems.

Blisk facts and figures are impressive: It takes between 15 and 60 hours to make one workpiece, depending on the size of the component and the type of machining that is required. The parts that are produced are worth between 30,000 and 60,000 Euro. This makes the constant monitoring of the tools that are used to machine them so vital, for if there is a problem in the production process because of a faulty, worn or incorrectly fitted tool and the work is scrap, things can quickly get very expensive. Each component can require the use of about 10 different tools – from the humble twist drill to expensive special purpose tools. At MTU in Munich there was the odd occasion when the wrong tool was fitted in error, resulting in substantial losses. With the laser they can now be confident that such mistakes cannot happen again.

The laser systems also help maximise the utilisation of the machines. After all, in modern production facilities of the kind found at MTU where manning levels are low, there is not an operator on every machine all of the time. One operator is often responsible for several machining centres, so without a reliable monitoring system, if there is a problem with a tool it can take a long time for the fault to be found. The tool may be broken or it may be worn or its cutting edge may have burst, ruining the surface of the component.

This is particularly true on weekends when running the machines unmanned on Saturdays and Sundays is essential because of the production costs of the products. “Our ultimate goal – to achieve the greatest possible machine utilisation – means working toward the industry standard of 5,000 hours per annum. The longer the machines run, the more we can keep costs down. This can only be achieved by working unmanned weekends,” explains Heinz Baumgartner – “And with the support of LaserControl NT,” adds Winfried Weiland, sales engineer at Blum-Novotest.

This is also why the production experts at MTU Aero Engines plan to take a different approach to tool breakage in future, one in which the laser measuring system will again take centre stage. What is proposed is to interpret the error message, so if the laser detects a broken tool, a sister tool will be fitted automatically. This degree of automation will further enhance machine utilisation by cutting unnecessary stoppages to an absolute minimum. The function is built in to the Blum measuring cycles as standard.

The excellent process stability which the laser systems offer benefits other areas as well – most of the machines that are equipped with LaserControl no longer require devices for tool presetting. Some machining centres are operated in parallel, but MTU’s objective is to dispense with tool presetters altogether in future, so when the machines are fitted with new tools, the laser will capture the tool data to the nearest µm directly on the machine. This will eliminate human error when operators manually enter tool data that has first been logged on the presetter, such as keying errors and transposed numbers. Measuring directly on the machine is in any case much more accurate, as the data are recorded in the actual clamping situation and at working speed. All kinds of tools are measured with the laser measuring systems. The smallest has a diameter of just 1.2 mm, while the largest cutter head is currently 250 mm.

MTU also sees significant benefits from the NT technology introduced by Blum in 2003 which has completely eliminated occasional problems previously caused by coolant. “On this basis we can now theoretically move to the laser with the tool dripping with coolant and it still works perfectly. Together with the tool cleaning jets which were installed a few years ago, this solution represents a real quantum leap in process reliability. The good direct contact which we have established over the years with Blum is a major contributing factor. The same goes for the custom cycle which Blum have written to allow special-purpose tools with their non-standard profiles to be measured,” says Walter Strohmeir.

MTU has also been able to use LaserControl to help solve a problem that occurs in day-to-day practice – because of the long operating hours, the machines can experience thermal growth which can adversely affect machining quality. LaserControl compensates for this effect by calibrating between machining steps. This means that the thermal growth in the machine axes or spindle that is found by calibration is stored in the controller as an additive zero offset.

“For us, it is the process reliability which LaserControl NT offers that is its most important feature. The excellent cooperation with Blum is another vital factor for our business because they understand what we want and can deliver it quickly. And they are always giving us useful hints, like how we can measure the tools even faster. Above all however, the laser measuring systems give us the reliability and confidence we need for our machining processes,” sums up Walter Strohmeir with evident satisfaction. Passengers too should enjoy peace of mind thanks to the high quality standards set by MTU Aero Engines, at least whenever their flights are powered by engines from MTU.

German  Summary

Qualität hat in der Luftfahrtindustrie oberste Priorität. Und weil das so ist, setzt beispielsweise der Flugtriebwerkshersteller MTU Aero Engines in der Fertigung konsequent lasergestützte optische Messsysteme ein. Damit erreicht die Prozessstabiliät konstant genau jenen hohen Level, der zur Erzielung bestmöglicher Fertigungsergebnisse unumgänglich ist. Der deutschsprachige Beitrag ist nachzulesen auf:
www.aerotec-online.com/aero0111mtu

Weitere Beiträge

→ MTU Aero Engines: New factory in Poland
→ Aircraft tooling under control
→ MTU and General Electric jointly develop innovative repair processes
→ Low-cost laser labelling
→ Making serial parts out of metal powder