CNC Retrofit Gives New Life to Old Mills

Stellex Monitor Aerospace Inc. (Amityville, NY) operates 10 Cincinnati Milacron gantry-style milling machines to produce titanium and aluminum alloy aerospace components. A CNC retrofit-completed on five units so far-has given the machines a new lease on life.

Originally equipped with Cincinnati’s Acramatic controls, the mills now have new digital servomotors, drives, and CNCs supplied by the Machine Tool business unit of Siemens (Elk Grove Village, IL). The Sinumerik 840D controls run on a Windows XP platform, and provide true 3-D five-axis cutter compensation and kinematic transformation.

According to VP Gary Kahrau, benefits from the retrofit include reduced setup time, improved part surface finishes, fewer secondary finishing operations, and significant improvement in overall productivity.

The oldest mills retrofitted were built in 1978. “They actually perform better now than when they were new, owing to the significant improvements in control technology,” Kahrau says. “The Sinumerik CNCs include several features for five-axis aerospace cutting simply not available from other control suppliers.”

One such feature of the open-architecture controls is real-time, five-axis kinematic transformation capability called TRAORI, which eliminates postprocessing and the potential loss of part geometry information. By directly accepting part data, the CNCs can reproduce smooth, accurate toolpaths and provide accurate 3-D cutter compensation.

When Stellex runs the same part on different machines, TRAORI compensates for the particular machine kinematics, minimizing the need for part programs for each machine configuration and providing flexibility to move production from one machine type to another. The controls can also accept program data from a post-processor, allowing Stellex to use previously developed programs if desired.

In addition to the CNC retrofit, Siemens also provided a dynamic machine engineering analysis called Mechatronics. The three-step process involves collecting real-time machine performance data, establishing optimized CNC and servodrive parameters, and verifying the resulting machine performance. Kahrau says the process cut rotary axis error on the five-axis gantry machines in half. Circle 224



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