CNC Retrofit Improves Accuracy And Productivity For Aerospace Components

Stellex Monitor Aerospace Inc. (Amityville, New York) has completed a total CNC retrofit on the fifth of its ten Cincinnati Milacron gantry-style milling machines, which are used in the production of titanium and aluminum aerospace components. The turnkey retrofits were provided by the Siemens Machine Tool Business (Elk Grove Village, Illinois).

Originally equipped with Acramatic “Big Blue” controls, these machines now have Siemens digital servomotors and drives, Sinumerik 840D CNCs running on a Windows XP platform with 3D five-axis cutter compensation and full five-axis real-time kinematical transformation. According to Stellex Vice President Gary Kahrau, the results have already been documented to include reduced setup time, improved surface finish, reduced secondary finishing operations and significant improvements in overall productivity.

The company operates a 250,000 square-foot modern facility. There, it produces struts, spars, landing gear, bulkheads, crown beam assemblies and other medium to large parts from titanium, aluminum and stainless steels for commercial and military aircraft and aerospace vehicles, including space shuttles.

Mr. Kahrau elaborates on some of the 840D features that are benefiting the company. “The open architecture of the control allows us to create our own screens and integrate with our ERP system,” he says. “We store all of our own data on a proprietary ERP system. The data files are dispatched to the CNC, where our custom Shop Workstation program resides. It handles the handshake of the data files with the control. This program is fully integrated with the control’s tool management system as well.”

With the real-time five-axis kinematical transformation called Traori, the 840D control can directly accept the part’s workpiece definition data.

“With the extreme metal removal rates, deep pockets and long contours typically encountered in aerospace production, this feature of the CNC has demonstrable upsides every day for Stellex,” says Mr. Kahrau.

He further expands upon the open HMI of the CNCs being retrofitted on the Stellex machines. “A cutter diameter compensation and customizable tool management system onboard the 840D give operators quick and accurate information in real time, plus it has the capability to accept additional features as the application demands,” he explains.

Siemens also provided Stellex with an advanced dynamic machine engineering analysis called Mechatronics. First, it collects critical real-time machine performance data, and then it establishes optimized parameterization of the CNC and servodrives. Finally, the analysis verifies optimized performance of the machine. Mr. Kahrau cites the servo analysis, ball bar tests, acceleration/deceleration tests, bi-direction compensation work-up and other protocols as being key to the end results. “Our machinery accuracy is better now than when the machines were new, our five-axis gantry has never performed so well and the rotary axis error was literally cut in half.”