New EDM Cuts Turbine Fir Tree Challenges Down to Size T
he AgieCharmilles CUT 200 Dedicated, at first glance, appears the same as any other wire-EDM system from GF Machining Solutions. However, the company has transformed it into one specifically for
larger, heavier aerospace applications—in particular, machining the fir tree patterns on jet engine turbine parts.
As the aerospace industry implements tougher materials, the new AgieCharmilles CUT 200 Dedicated gives manufacturers an alternative to conventional machining processes, such as broaching, when it comes to generating fir trees geometries. In fact, preliminary analyses shows that the cost of the wire-EDM process is approximately 40% less compared to broaching while maintaining similar productivity levels. Broaching shears material and in the process can harden part surfaces. These hardened surfaces, in turn, cause the broach to wear and dull. So instead of one broach imparting about 100 tree patterns, it might last for only 20, and the tools are expensive to replace. EDM, on the other hand, is cost effective and cuts any shape in challenging materials. Plus, EDM provides the versatility to quickly changeover to cut new shape geometries, whereas broaching requires, in most instances, between nine months and a year to develop a completely new tool. Since several EDMs replace one broaching system, manufacturers also gain increased production reliability. They avoid operations coming to a halt because a broaching machine is down. Additionally, having multiple EDMs as opposed to one or two broaching systems gives manufacturers the option to spread production capacity to different global locations if needed. The key design changes and features of the AgieCharmilles Dedicated line of machining solutions include a new innovative A/B rotary table, in-process probing and the company’s e-Tracking software as well as other software functionality. The new table system not only enhances the process of EDMing large, heavy aerospace parts, it allows the machine to be easily automated. In the development of the new machine, workpiece weight was a main factor, and one
the company overcame with its special nonconventional, nontrunnion- style table. It is a rotary table with B-axis rotation and +25/−25º A-axis tilt, both of which ride in a horizontally orientated crescent-shaped axis that provides a swaying motion to the right and left. The table allows the CUT 200 Dedicated to handle much heavier loads—up to 551.16 lb (250 kg)—without the risk of flexing. What differentiates the GF Machining Solutions design and gives it strength is that the table is actually built down into the machine itself.
In the past, machine tool OEMs would locate A/B tables on top of
a machine’s existing standard table. Unfortunately, workpieces would then sit too high, which required extremely tall Z-axis travels. And, with workpieces so high, the machine’s lower flush nozzles were further away from the work zone—making for poor flushing conditions and diminished cutting speed and accuracy.
GF Machining Solutions removed the table of its standard AgieCharmilles CUT 200 wire EDM, bored out a cavity underneath the machine’s casting and installed the new style table. Doing so eliminates issues with part weight and its affect on the table. Plus, the design is one that locates the tilt motion directly under the worktable clamping surface for even more load support and accurate table motion. Since all GF Machining Solutions machine bases are polymer granite, the AgieCharmilles CUT 200’s existing base provides more than enough strength, stability and rigidity for the new table design. Workpieces also sit lower in the machine, so the machine’s lower wire guide head is very close to the work zone to deliver excellent flushing conditions, which in turn allows for increased cutting speed and accuracy.
With large aerospace jet engine parts, automation on wire EDMs with standard A/B tables has always been extremely difficult, if not impossible. Standard tilt tables take up a lot of a machine’s work envelope and restrict a robot’s maneuverability to load and unload parts.
The AgieCharmilles CUT 200 Dedicated was designed specifically for larger, heavier aerospace applications.
The table design of the AgieCharmilles CUT 200 Dedicated allows for easy automa- tion. For that same reason, GF Machining Solutions removed all the power cables from the machine and rerouted them at the back of the work envelope to further clear the workspace and eliminate any interference. Additionally, the upper and lower guide heads move out of the way to let a robot enter for loading and unloading.
All the generator functionality on the AgieCharmilles CUT 200 Dedicated is geared toward tough aerospace materials such as
titanium and Inconel. The machine’s advanced generator technology— developed and tested through years of research with aerospace OEMs, universities and other academic institutions—ensures surface integrity in both those materials while it eliminates any visible recast layers or micro cracks after four trim cuts.
While the AgieCharmilles CUT 200 Dedicated’s intent was aerospace turbine applications, it is also well suited for components in the energy and power generation industry sectors. ME
November 2014 |
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