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FEATURE SPRINGS & SHOCK ABSORBERS REDUCING
MACHINE TOOL VIBRATIONS
Anders Digernes, R&D manager at
Sandvik Coromant, tells the story of an innovation in vibration damping
T
he Taipei 101 building, one of the tallest structures in the world, is located only 660ft from a major fault line, so
earthquakes and high winds are a serious threat. However, it is also home to the world’s largest dampers – measuring 18ft across. The tuned mass damper, which can reduce up to 40% of the tower’s movements, has saved the building from disaster on multiple occasions. While reducing vibrations in machine tools doesn’t exactly work in the same way, the two applications share a common goal – to deliver greater stability and combat the risk of error. Silent Tools has been a part of the Sandvik Coromant product offering for several decades, but what is it? Silent Tools started as the ambition of a
university student. In 1964, when writing his thesis on tool vibrations, Hans Kristian Holmen created a concept for an anti-vibration boring bar. His work almost remained no more than a university project, until its potential was spotted by a visitor, who saw the prototype in a lathe in the university workshop. Plans to manufacture the prototype later began, supported by a spike and nail factory located in Norway, which began to produce the damped tools. The manufacturer then partnered with Sandvik Coromant in the 1970s.
GOOD VIBRATIONS Vibrations can lead to inaccuracies in the machined part’s dimensions. As the cutting tool vibrates or chatters against the workpiece, it may deviate from its intended path, resulting in dimensional inaccuracies and poor surface finish. They can also cause irregularities on the surface of the machined part, which is particularly problematic in applications where a smooth surface finish is critical, such as in precision machining or industries like aerospace and medical. In addition, when the cutting tool vibrates
excessively, it experiences higher levels of stress and fatigue, which can shorten its lifespan and compromise the quality of machining. Vibrations may necessitate slower cutting speeds and shallower depths of cut to maintain acceptable quality standards, thereby increasing machining time and reducing overall throughput. In short, vibration-prone operations pose
a constant threat to productive and secure machining, especially when dealing with long overhangs or deep cavities. Reducing process parameters such as depth of cut, speed or feed, is one aspect to consider, but it will most likely have a negative impact on productivity.
ENHANCING EFFICIENCY Dampers work by absorbing, dissipating or redirecting the energy created by vibrations, thereby minimising their effects on the machining operation. Silent Tools uses a specialist technique known as tuned mass damping, where a counterweight within the tool absorbs kinetic energy of vibrations and uses a compensating frequency to eliminate them mechanically, rather than converting them into noise and heat. With the smallest configuration of the tool just 10mm in diameter and the largest at a record-breaking 600mm, Silent Tools can support a variety of machining operations for turning, boring and milling. For instance, machining deep holes is a particularly vibration-prone operation, especially when machining with long overhangs. Damped boring bars with overhangs from six to 14 times the diameter enable higher metal removal rates compared to non-damped boring bars. Helping ensure high-quality surface finish, as well as meeting the demanded tolerance, the higher cutting parameters that this machining strategy allows for creates shorter chips, thereby improving chip evacuation at the same time. This is critical when machining with long overhangs. Because Silent Tools allows for more
aggressive cutting parameters while maintaining quality and productivity, users are able to reduce machining cycle times and therefore enhance overall efficiency in metal cutting operations. We find that, when using Silent Tools alongside Sandvik Coromant tools and adaptors for their chosen application, customers make productivity gains of at least 50% when shorter adaptor lengths are used, and up to 300% for longer adaptors.
AN EVOLVING TECHNOLOGY Silent Tools continues to evolve – including upgrades in 2024 designed to deliver a more consistent performance and even better surface finish. The damper body, previously requiring
56 DESIGN SOLUTIONS JULY/AUGUST 2024
manual fine-tuning, is now automatically assembled and each and every damper is calibrated by a machine. This automation results in a highly precise and predictable frequency area, perfectly matched to each adaptor’s intended overhang and application. This means that Silent Tools turning adaptors are more efficient at countering vibration forces at long overhangs than ever before. To further ensure accuracy in set-ups and optimal tool health, the upgraded turning adaptors are accompanied by the introduction of digital device Tool Status Checker. This is designed to help operators check tool health and support tool set up before machining begins. It is compatible with all versions of Sandvik Coromant turning adaptors. Users simply need to snap it onto the adaptor’s serration lock interface using the built-in magnet, download the software, and it’s ready to go. With Tool Status Checker’s centre height setting feature, a precise set-up is guaranteed every time, while the temperature monitoring feature ensures that the adaptor is always working within its specified temperature range. Silent Tools doesn’t, however, need to act
alone – customers can learn more about their machining operations with Silent Tools Plus. Using a connected turning adaptor and sensors to monitor load, vibration, deflection, surface finish, temperature and in-cut detection in turning applications, this overcomes the challenge of operator-blindness in internal turning. Because an operator has no visuals of the process in question, it was previously extremely difficult to identify potential problems until turning was complete. By streaming data directly to a dashboard,
Silent Tools Plus provides operators with a view of the cutting zone, allowing them to identify problems such as excessive deflection, vibration or set up issues before they escalate and manufacturers are forced to scrap expensive components. Also available as a machine- integrated version, with CoroPlus Connected, data generated at the cutting zone can be automatically transformed into cutting actions, eliminating the need for operators to monitor the machine dashboard for the entire process.
Sandvik Coromant
www.sandvik.coromant.com
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