Special machine building: XXL high-precision mirror

For an even clearer view of space, astronomers worldwide need a new generation of high-power telescopes. German company OptoTech joined forces with Siemens to develop a special machine to manufacture the large, high-precision mirrors required for such telescopes.

13 billion light years – nearly back to the Big Bang – is how far our view into space might reach in the future. A new generation of large telescopes should make this possible. Yet these super-eyes require a large number of highly precise and very large mirrors. And it is a complicated process to manufacture them. The main mirror of this kind of telescope alone consists of around 800 mirror elements with a diameter of about 1.5 meters each and a thickness of just 50 millimeters. Every element has to be precisely manufactured to within a few nanometers.

 

The solution: As the largest and most state-of-the-art precision optics machine in the world, the UPG 2000 CNC provides maximum precision when it comes to the grinding, lapping, and polishing of optical components for astronomical applications – all in a single machine. It was designed and built by a multi-talented company, OptoTech Optikmaschinen GmbH. As a global market leader for optical machines, this company has been using Siemens technology in its development and manufacturing for many years.

 

“We developed this universal machine specifically to make mirrors with diameters of up to two meters and for other large optical components,” says Jochen Franz, the head of the design department at OptoTech. The objective is to achieve a production accuracy of 30 nanometers, equivalent to about one-thousandth the diameter of a human hair.

A multi-talented heavyweight

In contrast, everything about the UPG 2000 CNC itself is big: its total weight (86 metric tons), the granite block upon which it rests (40 metric tons), the mirrors it manufactures, and the challenge posed by its design.

 

A project of this kind doesn’t allow for any mistakes – no expensive prototypes that don’t function properly, no processes that will cause snags during operation, and certainly no mirrors produced without the necessary precision. It was clear to OptoTech that only a completely new and complex combination machine would make it possible to achieve the required production quality. “Switching from one machine to another always results in lost time and precision. That had to be avoided,” says Roland Mandler, founder and CEO of OptoTech.

Development in record time

Despite the amount of pioneering work that was required, OptoTech collaborated with Siemens to develop the UPG 2000 CNC in just 18 months. To accomplish this, the optics experts relied on NX PLM software from Siemens. The integrated software suite for product development and manufacturing provides for even multidisciplinary calculations. “NX and the integrated development environment don’t just make better products. Faster development, design, and production also significantly reduce the time to market,” says Peter Scheller, the NX Marketing Director at Siemens in Germany.

 

The designers at OptoTech initially created a virtual 3D design. NX incorporated all important parameters as realistically as possible into the design, including, for example, machine mathematics and properties of the Sinumerik 840D sl Siemens control system used and of the Siemens Sinamics drive. A team from Siemens Mechatronics Support subsequently simulated and optimized the virtual machine that was created during this process.

 

Thanks to the virtual design process, expensive physical prototypes and the time-consuming parallel element method of calculation are things of the past. This kind of calculation is usually needed to verify whether a design will be structurally sound in the real world. The CAM module for the production simulation even made it possible to simulate the production path for the mirrors at OptoTech. “This facilitates virtual commissioning at an early stage of the process,” explains Scheller.

NX and the integrated development environment reduce the time to market substantially.
Peter Scheller, Siemens Industry Software

Advantages of integration

The advantages of NX-supported development are obvious even after commissioning: NX is deeply integrated into Teamcenter, the Siemens platform for Product Lifecycle Management (PLM).

 

In terms of drive technology, OptoTech benefits from the Integrated Drive Systems approach used at Siemens. Integrated drive technologies offer considerable advantages for a complex project like this one. The horizontal integration of the drive train ensures a smooth coordination and the optimal dimensioning of all subassemblies, from the converter to the motor and couplings to the gearboxes. With regard to vertical integration, these systems are optimally engineered, configured, and networked all the way to the control level thanks to the world of Totally Integrated Automation. And Integrated Drive Systems include integrated customer support over the entire service life of a machine.

 

A successful working relationship over many years and development assistance play key roles in OptoTech’s selection of a development partner – as did the technology: “No other provider of control systems offers a premium CNC that is openly scalable and has a modular design like Siemens does,” explains Franz, head of the design department. “For example, with the Sinumerik 840D sl, we can simply adjust the number of axles on the control side and set the necessary axis interpolations as we see fit.” He says that it is just as fast and easy to adjust the customer-specific user interface. The ability to use remote maintenance to access the Siemens CNC is yet another advantage.

2015-10-01

With more than nine million licensed users worldwide, Siemens is one of the leading providers of Product Lifecycle Management (PLM) software.

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