Siemens Industry, Inc.
Munich, Germany

DMG MORI manufactures a wide variety of conventional chip-cutting and ultrasonic machining centers for OEMs and production job shops serving the aerospace industry. Inherent in this industry are several factors that require great care and planning in the machining process. Typical components produced include those made from very lightweight but hard materials such as titanium and related alloys, as well as aluminum workpieces where substantial volumes of material must be removed, such as fan blades and bladed disks known as blisks. Due to very long cycle times and often high raw material costs, the machining of such components has long presented a challenge to part production departments and job shops alike.

On two recent applications, DMG MORI turned to long-time business partner Siemens for assistance. By offering a total package of CAD-CAM-CNC hardware, software and engineering services, Siemens was able to help this machine builder substantially improve part production by reducing design-topart protocols and machining time while improving tool life, surface finish, dimensional accuracies, and overall production efficiencies.

In the first instance, a reverse thrust component for a jet engine was to be made from Ti Gal-4-V, a material often used in aerospace, owing to its elastic stiffness. Starting from the CAD file, the Siemens PLM (Product Lifecycle Management) team ran the program through its NX CAM with a VoluMill add-on feature that calculates for maximum material removal rates. The User Defined Events (UDEs) feature inside the NX program allows simple check boxes for triggering post-processor references for coolant pressure, amplitude, ultrasonic generator settings and more. This avoids manual programming and, as a result, reduced the program transition time from as long as two days to approximately 30 minutes.

Once the program was ready for the control, the features of the Sinumerik 840D sl CNC allowed a more streamlined simulation of the actual cutting path. The 3D quick set compressor feature provides a parametric itemized data file for all path motions, thereby eliminating collision and ensuring the optimum tool path, in conjunction with the NC kernel and PLC on the machine tool.

The high-speed machining feature is highlighted by Cycle 800, which is a static plane transformation that allows a 5-axis machine to define a rotated working plane in space. It is commonly known in the industry as 3+2 programming. The cycle converts the actual workpiece zero and tool offsets to refer to the rotated surface. Of note here, the cycle accommodates particular machine kinematics and positions the physical axes normal to the working plane. This is referenced as TRAORI or transformation orientation. Meanwhile, the Sinumerik CNC Operate user interface on the machine allows the operator to perform a variety of integrated tool management and information management functions, all transportable on a USB or network connection.

In the simulation, the loading and fixturing of the workpiece is performed virtually in NX CAM, which also calculates a consistent chip load, critical in these large material removal applications. The simulation further verifies the tool length at every cutting section and the program is finalized for the machine to begin. It is literally like working with a “Digital Twin” of the machine.

During production, this process yielded a 2.25× improvement in tool life on this very hard material. The finished part was run in 4-½hours with a surface finish improvement from 62.5 Ra to 35 Ra, due to the ultrasonic actor.

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