Jet engines are high-tech products and their production requires implementation of innovative technologies and processes. MTU Aero Engines constantly develops innovative manufacturing strategies and if necessary, obtains additional external expertise. As such, the company contacted HAIMER to seek help in optimizing the demanding machining process of manufacturing frames and castings. Difficult-to-machine materials, high-quality components and the high degree of automation at MTU required an absolutely smooth and reliable machining process to maintain the highest levels of quality. In order to ensure this consistency and to control the high axial cutting forces during machining, the company decided to implement the Safe-Lock pull out protection system from HAIMER.
In the Safe-Lock system, special drive keys in the tool holder and grooves in the tool shank prevent the cutting tool from spinning during extreme machining. Hence, it prevents the tool from being pulled out from the chuck. In addition to the frictional clamping forces of the selected clamping system, the cutting tool is held using positive form locking in the tool holder through the constructive design of the system.
While explaining the decision for the system, Senior Manager NC-Programming Stator Components, MTU Aero Engines AG, Alexander Steurer says, “Through the introduction of Safe-Lock and the shrinking technology from HAIMER, we can guarantee process reliability even with milling challenging high temperature materials. This is a prerequisite to guarantee smooth processing during manufacturing of frames and castings, given our high degree of automation.”
The combination of pull-out protection and highest concentricity of the system leads to low vibration and as a result, a very stable machining process. Due to the increased cutting depths and feeds, the metal removal rate can be increased significantly. And thanks to the improved runout accuracy of shrink fit chucks, tool life is improved by up to 50 per cent.
The system offers runout of less than 3 μm coupled with optimum balance. In addition to this, the possibility for easy length presetting were substantial reasons for MTU to switch to the HAIMER system instead of continuing to use Whistle Notch or Weldon tooling systems. While these other systems prevent tool pull out, both are unsymmetrical by design, hence providing insufficient runout and balance accuracy.
Through the use of a set screw, the cutting tool is wedged against the opposite wall of the clamping bore. The holder pushes the cutting tool off center and thereby leads to excessive amounts of runout. Any such design also allows for significant radial play between the tool shank and the bore itself. That way the aforementioned holders actually push the cutting tool off center, thereby inducing excessive amounts of runout. Line Manager Machining Stator Components, MTU, Hans Drahtmüller explains, “Due to the deteriorated runout, the tool life could not be fully realized. As a result, the tools with a Weldon flat had to be exchanged early. With Safe-Lock regrinding could be automated due to the cylindrical form of the system, as the cutting tools no longer have to be inserted manually into the grinding machine as compared to Weldon flat tooling. This saves tool costs!”