Looking at the peening process, one is likely to focus on the machine's capabilities, but to underestimate how demanding it is to find a good concept for the work piece fixtures.

To have access to fixtures which take advantage of the machines capabilities can increase the productivity of the process to a great extend. Therefore it is important that the operators communicate with the design engineers since the solution is in most cases based on the movement flexibility of the nozzles as well as the number of nozzles being used.
On top of that one has to realize that  peening causes a very abrasive surrounding. On one hand the parts have to be masked where they require no peening, on the other hand the fixtures have to be protected well to insure that they are not destroyed in a couple of weeks.

Various Different Engine Types to be Treated

The peening department of MTU Maintenance Hannover GmbH in Germany is an excellent  example of a workshop trying to develop the best possible fixture for its parts. In this particular case they have to peen huge numbers of blades from various different engines such as General Electric's CF6-50s and CF6-80s,  Pratt & Whitney's PW2000 of  and IAE's V2500. Depending on the blades, peening media of the size S110, S170 or S230 is used reaching the required intensities between 0.15-0.25 Amm.

Average Peening Time per Work Piece  is 40 Seconds

The design of the fixture had to fulfil many requirements. The basic frame of the fixture had to be able to hold as many blades as possible. In addition, it had to be suitable for different types of blades. Furthermore only the roots of the blades had to be peened and the rest had to be protected. The solution was to place a total of 20 revolving satellites on the outer diameter of a ring fixture, which was placed on the turntable. This turntable is indexing the satellites one by one in front of the peening nozzles. Using this solution, the average peening time per piece is only 40 seconds.
In order to take credit for the different types of blades, various replaceable insertions were designed, which can be slid into the satellites. To make those insertion abrasive resistant, a silicon material was chosen.

Of course, such sophisticated fixture concepts are not cheap, however, they are certainly a cost effective solution looking at the increased productivity.

For information:
MTU Maintenance Hannover GmbH
Müncher Strasse 31
30855 Langenhagen, Germany
Tel: +49.511.7806 4471
Fax: +49.511.7806 660
E-mail: mtu.maintenance@haj.mtu.de
www.mtu.de