High-end CNC turning and milling machining– with Redex linear drives
Backlash-free slide drive for high quality machining.
www.redex-group.com
With the MC series, NILES-SIMMONS offers CNC turning and milling machining centres that combine maximum precision with a high degree of flexibility and adaptability. These machines are very much in demand in the aerospace industry, for which they were originally developed, but demand also comes from other sectors. The slide drive from Redex, a backlash-free rack and pinion drive with two preloaded planetary gears, contributes to precise and efficient machining with complete part accuracy down to +/- 2 µm.
This is CNC turning and milling machining at the highest level: With the N40 MC machining centre from NILES-SIMMONS, users can manufacture rotationally symmetrical components up to nine meters in length, with a swing diameter of up to 1,100 mm and a weight of up to four tons in a single clamping and, if required, as a closed door machining process. Various operations such as turning, milling, grinding, and measuring are integrated, all with high precision. The 60° slant bed technology of the steel welded frame with concrete filling makes a significant contribution to machining accuracy.
Target application: high-precision complete machining for the aerospace industry
This machining centre is principally deployed in the aerospace industry, which also uses the smaller and larger models in the MC series, from the N20 MC to the N60 MC. Some parts they are used to manufacture have to enduring high stresses, for example in aircraft landing gear.
This type of application is virtually built-in to the machines from the design stage. Carsten Hirche, project manager for the N40/N50/N60 series at NILES-SIMMONS explains, “The goal was to develop a new generation lathe in collaboration with a leading international supplier of jet engines. However, the series is also used in the oil and gas industry and for general heavy-duty machining, in other words, wherever complex workpieces with extreme demands in terms of precision and stability have to be manufactured.”
Modular options, flexible machining
The characteristic profile of these machines, the N40 MC in this case, can be summed up as follows: It can be designed as a single or multi-slide machine, offers maximum precision, and is also very user-friendly and extremely flexible. The modular system allows variable machining units to be added, and with different tool systems, tool magazine sizes, and a wide range of options, users can tackle even the most demanding machining tasks. They can also adapt the size of the N40 MC to their requirements: The machining centre is available in several nominal lengths.
The challenge: to design a powerful and high-precision slide drive
One of the many tasks that the design team had to tackle during development was the selection of drive concepts that meet the highest requirements for positioning and machining accuracy. The users can choose between an electronic spindle direct drive and various gearbox versions.
For the bed slide, the designers at NILES-SIMMONS opted for a rack and pinion drive from Redex. This enables fast machining processes for large components. Key specifications: The maximum travel speed is 30 m/min with an acceleration of 3 m/s² and a moving mass of up to 4,500 kg. Depending on the design, the machine can achieve a feed force of up to 30,000 N.
Decision favoured an electrically preloaded rack and pinion drive
And while these specifications are already impressive, they don’t say anything yet about the precision. Carsten Hirche continues, "The accuracy requirements, which are being fulfilled, are very high. The machine must guarantee maximum precision and freedom from play even under high forces and accelerations." Here's another number: we get repeat accuracies in the µm range, with overall part accuracy of up to +/- 2 µm.
Why was the DRP2 series from Redex chosen for this application? “The factors that counted in the decision were power transmission, vibration behaviour, accuracy, and space-optimized integration into the machine concept.”
DRP: high-precision, backlash-free linear drive
DRP drives consist of two high-quality planetary gears combined in a torsion-resistant monoblock. Two integrated output pinions engage with the rack and, via the electrical tensioning of the motors, create the desired preload of the pinion-rack drive to enable highly precise and backlash-free movement of the drive.
This design concept fits well from a theoretical and practical point of view and enables designers to achieve greater travel distances and accuracies compared to ball screws, which also have limitations in terms of achievable machining accuracies on the workpiece due to high travel speeds and temperature development on the machine frame.
The NILES-SIMMONS team are fully satisfied not only with the actual drive hardware, but also with the cooperation during the project planning phase. Carsten Hirche summarizes, “Redex provided us with excellent support, and we always received competent answers to our questions.” And the result speaks for itself: The N40 MC is used worldwide in highly demanding applications, not just in the aviation industry.
www.redex-group.com
