22/03/2007
CERATIZIT heavy machining of wheel sets
Where trains of the Austrian railway association (ÖBB) make their pit stops |
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At CERATIZIT 'energy and transport’ is a cutting tool end-user segment. In this segment CERATIZIT develops high-quality solutions for complex machining operations in the aerospace industry and manufacture of turbines, electric motors and railway vehicles. The reprocessing of railway wheels is part of the railway machining segment, for example at the Austrian railway association ÖBB, a CERATIZIT customer with a site in Salzburg. The place where ÖBB trains make their pit stops.
The first special insert tools for the machining of railway wheel sets (in addition to trains, underground and tramway vehicles are also part of this group) were launched on the market by CERATIZIT around 35 years ago. “In order to be successful in this sector a meticulous analysis of the factors influencing the machining operations is necessary,” says CERATIZIT product manager Markus Krabichler. The expert for difficult machining tasks states: “Only with our comprehensive special knowledge and the continuous concentration on this special task have we been able to become one of the leading tooling suppliers in the field of railway vehicles. Both new concepts and the further development of existing solutions are part of our work.”
Smooth running surfaces for comfortable travelling
Railway wheels have a hard life: many kilometres on very different routes with heavy loads. As for every technical facility, the service life of trains decisively also depends upon maintenance. At the ÖBB Technical Service GmbH in Salzburg all trains receive a complete overhaul: skilled workers check the motors, control electronics and replace wear parts. An important point on their checklist is the reprocessing of wagon and locomotive wheel sets as well as ensuring the quality of these components. Train wheels are heavily used, give a correspondingly high degree of wear. “First of all train wheels for routes with a lot of bends or mountains are extremely stressed“, says Krabichler. “Particular attention is paid to the wheel surface quality of fast IC trains as these high comfort trains should provide the smoothest possible performance on long distance stretches.”
Time-saving inspections in the assembly pit
The most frequent cause of damaged wheel surfaces are quick braking actions. When braking suddenly, or also in a long braking action, a wheel can be blocked and will then be drawn onwards on the rail in this blocked state. In this way a flat and hardened spot is created, the wheel runs rough. The result: reverberation and vibration felt throughout the entire vehicle reducing the travelling comfort of the passengers.
But there is a remedy. Train wheels consist of forged steel which is why they can be re-machined several times. Locomotive wheels are inspected every 150,000 to 180,000 kilometres, wagon wheels every two years at the latest, depending on the route where they are applied. For example, a new wagon wheel in Austria has a diameter of 1,150 mm and can be turned down to a permissible minimum diameter of 1,086mm. Every time between 4 and 10 mm are removed of the diameter. When a wheel can no longer be machined, the complete axis with the two wheels is replaced.
More effectively usable cutting edges
The teams of the ÖBB Technical Service GmbH in Salzburg machine 24 axes a day on average, in two shifts at two underground machining centres. For such facilities a machine is placed in an assembly pit. The train or wagon is positioned above the machine, the wheels are machined without being removed in a complicated procedure. The machining of one axis (both wheels are machined simultaneously) takes between 15 and 25 minutes, half of the time used for measuring the degree of wear and the programming of the facility. In Salzburg the insert is indexed after 4 wheels for safety reasons. A development from CERATIZIT sets new standards. A square insert with 8 effectively usable cutting edges shows considerably longer tool life compared to the conventional tangential concept. Actually, with the tangential concept only 4 out of the 8 existing cutting edges can really be used. Furthermore the CERATIZIT tool holder system ensures particularly simple handling, and thanks to the carbide shims no cartridges are necessary, so the complicated cartridge change is eliminated. So, in addition to time saving there is also material saving.
Krabichler considers security an important aspect: “The position of the machine under the train makes swarf control – as there is risk of injury - extremely important. Our R70 and R71 are special geometries which have been developed for optimum chip guidancewhen reprocessing railway wheels“.
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