EDM From manual work to full automation

Source: Wolfgang Hanisch and Udo Baur* Reading Time: 5 min

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MTU Maintenance Hannover has significantly upgraded its production facilities with the addition of three new Exeron EDM 312 CNC 5-axis eroding machines. Six months after the investment, the company reports increased productivity, greater part precision, and reduced costs.

Detailed view: The erosion process on the cooling air bores of a turbine blade takes place at high-stress points of the component.
Detailed view: The erosion process on the cooling air bores of a turbine blade takes place at high-stress points of the component.
(Source: MTU Maintenance Hannover)

Three new EDM 312 CNC 5-axis eroding machines from Exeron, installed at MTU Maintenance Hannover in the winter of 2006, are an integral part of a comprehensive modernisation programme at the German engine specialist's production facilities for the repair and overhaul of guide vanes and blades.

Just over six months after the investment, Peter Stippler and Dr Hans-Henrik Westermann, both experts in mechanical manufacturing technology at MTU's Hannover site, are very satisfied: “We made a strategic decision with all stakeholders to expand our machining capacity to six axes and chose a system that allows us to machine workpieces in a single set-up. With this decision, we have significantly increased productivity, improved the utilisation of our manufacturing capacity, achieved greater and more consistent part precision and reduced costs”.


Exeron and MTU Maintenance Hannover, which as the heart of the MTU Maintenance Group is responsible for the maintenance of medium-sized and large aircraft engines, first came into contact in 2007. At that time, the implementation of a fully automated, integrated eroding system in a robotic cell for the highly demanding repair of high-pressure turbine blades was the only one of its kind.

In 2020, the first steps were taken in the now successfully completed project to develop automated EDM solutions for the repair of turbine segments. These core components of modern aero-engines place very high demands on manufacturing precision and also require maximum process reliability due to the stringent safety requirements placed on the parts and their immense intrinsic value.

More specifically, the newly developed process involves the machining of cooling air holes and sealing surfaces, which are geometrically characterised by small diameters, very narrow cavities and hard-to-reach webs and ribs, all of which range in size from 0.5 mm to 1 mm.

The components described also present other technological challenges that further complicate the EDM process and place particularly high demands on process control. In this case and for the machining process described, these are in particular

  • The lack of flushing in hard-to-access places due to the described geometries and undercuts as well as the very limited possibility to rotate the electrode in the areas mentioned.
  • A highly heat resisting superalloy as blade material.
  • The strict exclusion of micro-cracks, even in the case of material inhomogeneity due to built up repair material.

Prior to investing in the new equipment, the team at MTU had mainly relied on 3-axis EDM machines to machine complex vanes and blades. Although these machines produced good results, there was still considerable potential for productivity improvements. Their main shortcoming, in a predominantly manual process, was the considerable time required to set up the machines.

“In terms of process performance, we were nowhere near where we wanted to be,“ explains Peter Stippler. “With the old 3-axis machines, a lot of time was lost in setting up the machines and in planning and designing individual erosion fixtures”. Dr Hans-Henrik Westermann adds: “In addition, the frequent interruptions in the production process had a negative impact not only on productivity, but also on the precision of the parts, given the manual workpiece handling required by the machines.”

In addition to the time and cost savings that have already been achieved, the optimised machining process also ensures a high level of process stability, thanks to the precise and reproducible adherence to all the essential erosion parameters.

The success of the project is also due to the cooperation between MTU Maintenance Hannover and Exeron, which was based on partnership from the very beginning. The sales, development and application engineering departments of both companies worked together to identify the customer's optimisation potential and then successfully implemented the result in a tailor-made multi-stage system concept.

As part of this plant concept, the first stage of expansion involved the purchase of three state-of-the-art standard Exeron EDM 312 vertical EDM machines with rotary/tilt tables for 6-axis simultaneous machining and electrode changing systems, which would now allow all EDM tasks involved in the repair of guide vanes or blades to be carried out on a single machine. Inefficient machine changes and time-consuming set-up procedures are a thing of the past.

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From design phase to implementation

The rotary/tilting tables mounted on the machines were specially designed and built for these applications. “The implementation period of around two years was very ambitious,” says Udo Baur, Exeron's Sales Manager for Germany and Europe. “The first machine we delivered was already of decisive importance for the successful demonstration of a functioning manufacturing concept and has led to a total of three new Exeron EDM 312 machines now being used in Hanover.”

“We were able to exceed the customer's expectations with our proposals, and the MTU employees now working on these state-of-the-art machines are also responding extremely well to the new technology solution,” Baur continues. Peter Stippler believes that Exeron's comprehensive training programme, which provided the staff with competent and practical training, played a major role in this success.

Despite the current difficult economic situation, MTU Maintenance Hannover is literally always on the ball in terms of technology and is consistently pushing ahead with process innovations. “We are already well into the design phase for further expansion stages and our next step is to link our three EDM 312s via a central handling system. In this way, we want to further increase process efficiency and improve operator comfort,” explains Peter Stippler. In the future, it is also conceivable to move towards a fully automatic machining solution for individual blade types in order to be able to respond quickly and flexibly to potentially increasing customer demand. “It is quite possible that we will take further steps in this direction in the future, because our motto in the field of repair technology services is always 'Customer first, better every day',” adds Dr Hans-Henrik Westermann.

In any case, both partners are very similar in their assessment of the cooperation. Ambitious projects like this require experience and trust on both sides. In-depth process knowledge is also essential to develop the overall process in such a way that it meets the customer's high demands reliably and sustainably and can be implemented by the machine manufacturer in a functional and competitive manner. The cooperation between MTU Maintenance Hannover and Exeron has once again been an outstanding success, which is why the two companies will continue to work closely together in the development of new high-tech repairs and the associated implementation of demanding machining tasks.