Highly precise manufacturing of gigantic telescopes
September 4th, 2017. At 65 tons, 3.4 meters long, 4.7 meters wide and 2.8 meters high, the SCG 1500 is a high-tech machining center for highly sophisticated optics. "With SCG 1500 SCHNEIDER enters the exclusive market for the production of extreme macro-optics", emphasizes Gunter Schneider, founder and President of the SCHNEIDER group.
The construction of this extraordinary machine was commissioned by Green Optics. The Korean company is specialized in the production of large cylindrical lenses, prisms and mirrors for the space industry. With the purchase of the SCG 1500, Green Optics will contribute to the development of telescope systems and cylindrical lenses for the Organic Light Emitting Diode (OLED) screen technology. The SCG 1500 produces axial (rotationally symmetric) and non-axial (non-rotationally symmetric) aspheres and spheres, telescope mirrors, freeform lenses and cylindrical lenses. To produce a lens with a diameter of up to 1500 millimeters, the machine needs 80 hours with a simultaneous material removal of 40 kilograms.
In the course of the two-year development, SCHNEIDER repeatedly overcame unexpected challenges. "Since it was not possible to draw on existing components, we started from scratch and developed all components needed," emphasizes Dr. Klaus Hofmann, Manager Mechanical Design at SCHNEIDER. "Due to the enormous size of the components combined with extreme precision demands, we used the finite element method. We simulated the components in order to realize sufficient rigidity during machining with high accelerations," says Hofmann. Another major challenge was the enormous weight of the machine. Instead of producing the SCG 1500 at the headquarters in Fronhausen, the machine was transferred to the SCHNEIDER plant in Quotshausen that could carry the massive weight.
The machining center automatically changes the various processing heads used for the individual steps. All supply systems (electrics, hydraulics, cooling lubricant, pneumatics and sensors) are actively coupled. This way, highly accurate lens processing without reconditioning of the tools is possible. With one of the aggregates, a measuring head, the clamped lens can be measured inside the machine. If necessary, a subsequent optimized post-processing can be executed. To decouple vibrations from the surrounding area, the SCG 1500 stands on four air-bearing feet while the room climate has to be adjusted to +/- 0.5 Kelvin. To further increase production accuracy, the machining center is equipped with its own complex cooling system.
Even the transport of the machine was extraordinary: In order to transfer individual components to Quotshausen, special permits for heavy transport had to be obtained. In March 2017 the machine started its journey to Korea From Quotshausen to Hamburg, across the North Sea and the English Channel, through the North Atlantic Ocean and the Strait of Gibraltar into the Mediterranean Sea. Then, it passed the Suez Canal and the Red Sea, crossed the Gulf of Aden and the Arabian Sea and finally passed through the Strait of Malacca as well as the South China and East China Sea to Pusan. From there, the final special transport to Cheongju took place overland. The machine arrived at its final destination on June 13th, 2017.
On September 4th, 2017, Gunter Schneider and Dalibor Mikulic, Technical Manager for Precision Optics at SCHNEIDER, travelled to South Korea and participated in the celebration ceremony with Green Optics.