What could a machine tool have in common with Taiwan’s tallest building? Located in Taipei, the 1,667-foot-tall building could become victim to vibration if it wasn’t for its clever mass damper system. In turning, milling, boring and drilling applications, manufacturers could face the same dilemma. That is, if it wasn’t for Sandvik Coromant Silent Tools. Here, Anders Digernes, R&D Manager at metal cutting tools and manufacturing solutions expert Sandvik Coromant, tells the story of the innovation in vibration damping.

As one of the tallest structures in the world, located only 660 feet from a major fault line, earthquakes and high winds are a serious threat to the Taipei 101 building. Fortunately, at 18-feet across, it is also home to the world’s largest damper. The tuned mass damper can reduce up to 40% of the tower's movements, and 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 unique part of the Sandvik Coromant product offering for several decades, but what makes the solution stand out above the rest?
 

A brief history lesson

Silent Tools started life as the ambition of a university student. In1964, 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 and knew Holmen was onto something.

Plans to manufacture the prototype later began, then supported by a spike and nail factory located in Trondheim, Norway, who began to produce the damped tools. Later, in the 1970s, that manufacturer partnered with Sandvik Coromant to support the sales and distribution to the global market. Silent Tools has sat with Sandvik Coromant ever since, with the product area continuing to grow today.
 

Good vibrations

To understand why damped tool holders play an important role in machining operations, it’s first worth looking at vibrations. While vibrations can at times be useful — you wouldn’t get a very enjoyable sound from a speaker if it didn’t vibrate — in machining, they are not desirable.

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.
 

A silent hero

Dampers work by absorbing, dissipating or redirecting the energy created by vibrations, thereby minimising their effects on the machining operation.

Silent Tool™ uses a specialist technique known as tuned mass damping — just like Taipei 101 — 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 ten millimetres (mm) 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.
 

Maintaining our edge

For many years, Sandvik Coromant held a patent for Silent Tools that made the solution truly one-of-a-kind. Today, while concepts for mass tuned dampers are better understood by the wider market, there are many reasons why Silent Tools remains unique.

First, Silent Tools continues to evolve. That includes upgrades launched in 2024 designed to deliver a more consistent performance and even better surface finish. The damper body, previously requiring 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.

Tool Status Checker 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.

This leads us to another benefit of using Silent Tools. While an innovation in its own right, Silent Tools doesn’t 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, the product was brought to market to overcome 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.

Taipei 101 and machining at long overhangs share a common challenge — overcome by tuned mass damping. Silent Tools™ story may have started many decades ago, but continuous developments mean the solution offers manufacturers more than just a vibration eliminator. With Silent Tools, customers have greater visibility of the machining process, and therefore yield better results.
 

For more information visit www.sandvik.coromant.com