The world’s longest and deepest rail tunnel — the Gotthard Base Tunnel — opened in June 2016. The 57km twin-bore high-speed link under the Swiss Alps (linking northern and southern Europe) aims to replace one million lorry journeys per year.

The four tunnel-boring machines that were used to excavate the pair of 8.83m-diameter bores were built by Herrenknecht AG in Schwanau, southern Germany.

To produce many of the machine components out of wear-resistant steels, the manufacturer bought an RTT 30 bed-type milling machine with a B-axis swivelling milling head and integrated rotary table from the Spanish company MTE.

This machine is fitted with a Heidenhain TNC 640 CNC system, which can control both prismatic and turning operations and allows the company to simultaneously mill and turn in one set-up. Components up to 2,100mm in diameter x 1,500mm long and weighing up to 15 tonnes can be accommodated.

Programmer Uwe Liedl said, “The TNC 640 makes complicated machining ‘transparent’. Our machine operators are always given a choice between different strategies and can easily follow the cycles, so complex metal-cutting processes become clearer.”

Every year, Herrenknecht delivers standard components for assemblies that are worth 60 million euros; these include drill heads, cutting tools, transmission housings, rings and more. Parts are machined from wear-resistant steels such as Hardox 500 or fine-grained steel like S690.

In addition, spares have to be produced immediately, if there is a drilling machine failure on a construction site.