From January to the end of October 2018, the Old Town Astronomical Clock in Prague underwent a restoration project.

The goal of the restoration work was to give the watch its original look and original tuners of the 1960s.

During the Second World War, the astronomical clock was hit by bullets and subsequent fire severely damaged the clock. After the war, the clock was repaired to be fully functional again. More contemporary approaches were used to fix the clock. As a result, the whole mechanism consisted of both historical and modern-day parts. After the renovation, this cultural and historical monument was to return to a state that was both functionally and visually reminiscent of its original version.

The Czech Horological Society was aware of the benefits of 3D scanning technology and commissioned a project whereby the repairs were accurately documented by 3D scanning and saved for future repairs.

The project consisted of a highly accurate scan of the clock mechanism in order to generate a CAD model. Despite the challenges of the clock’s complex mechanism, the scanning engineers were able to create a complete scan of the clock with an accuracy of up to 0.078 mm. With the same accuracy, other parts that were previously dismantled were scanned. These included three handmade 1100 mm gears, a 640 mm spur gear and two smaller sprockets.

With such accurately scanned data, the team was able to commission the manufacture of critical spare parts. In addition, the 3D data can now be used anywhere in the world. Scans are stored in various formats for multilingual STL networks. These formats allow 3D printers, reverse engineering programs, and graphics programs to create visualizations and simulations.

In the end, the clock’s rich history and design have been documented to preserve this important relic.

See the full Metrology News article here.