Cutting tools with vibration control technology can substantially increase machining productivity on almost any machine tool or workpiece.
Uncontrolled vibration creates multiple problems in metalcutting operations. Varying forces in the cutting process cause vibration and tool chatter that degrade part surface quality, quickly wear or break cutting tools and damage machine tool components.
Passive/dynamic vibration damping enables productive, high quality machining with much larger tool length to diameter ratios.
Trends in product design have also created more vibration issues. To enhance product strength and reduce assembly costs, manufacturers are increasingly machining large “monolithic” parts, where a single piece replaces several previously assembled components. Producing internal features of these parts requires tools to reach into deep cavities, and the extended tool length further exaggerates vibration.
Attempting to minimize vibration by reducing cutting parameters decreases productivity and increases manufacturing costs. Instead, the best way to control this unwanted vibration is with passive/dynamic systems that utilize tuned mass damper concepts to absorb vibration before it progresses and disrupts the machining process.
Seco Tools uses this principal in its Steadyline® system of turning, boring and milling tools. Here’s more on what works, and what doesn’t, to control chatter in your turning and machining processes.
How Passive/Dynamic Vibration Damping Works
In metalcutting, vibration is generated by the changing forces that occur when making chips. The intermittent forces are apparent in the interrupted cutting process of milling and also appear in turning operations when the toolholder bar is periodically loaded and unloaded as chips form and break.
A passive approach to vibration control in machining operations involves maximizing the rigidity of elements within the machining system. For example, to restrict unwanted movement, machine tool manufacturers can utilize rigid structural elements, fill internal chambers with concrete or another vibration-absorbing material and make machines larger and heavier overall.
Damping is provided by a passive/dynamic system. Inside the holder’s
body a heavy metal mass counter-acts against the vibration created from
the holder’s flex during machining.
From a workpiece perspective, thin-walled parts and those with unsupported sections are prone to vibration when machined. To a limited degree, parts can be redesigned to improve rigidity, but such design changes can add weight and compromise product performance.
For cutting tools, a passive approach to vibration control requires the use of short, rigid tools and replacement of steel toolholders with those made of stiff tungsten carbide.
But manufacturers today want to achieve higher machining productivity without compromise to machine or workpiece. This is why manufacturers increasingly apply mass damper devices to overcome vibration. A tuned mass damper is a component suspended within a machine or structure that is designed to resonate out of phase with the unwanted vibration, absorb its energy and minimize the vibratory motion.
A passive/dynamic approach to vibration control for cutting tools applies the tuned mass damper concept. The Steadyline® system from Seco Tools, for example, features a pre-tuned vibration damper consisting of a heavy metal mass suspended inside the toolholder bar. The damper mass is made of high-density material to minimize its overall dimensions and absorb vibration as it is transmitted by the cutting tool to the body of the bar.
In the Steadyline® system, the vibration-absorbing mass is positioned at the front of the bar, where the potential for deflection is highest. In this position, the mass can dampen vibration immediately, following its transmission from the cutting edge to the body of the bar. The system also includes short, compact GL cutting tool heads that place the cutting edge close to the damping mass to maximize the vibration-absorption effect. The system is adaptable to a wide range of applications and is most useful in milling (contouring, pocketing and slotting), turning and both rough and fine boring operations.
With a standard tool (right) chatter resonates throughout the entire body of the
toolholder. With Steadyline® (left) the damper mass quickly absorbs vibration to permit higher cutting rates.
The Steadyline® system enables typical long-overhang operations to be performed at least twice as fast as with non-damped tools while enhancing part surface finish, extending tool life and reducing stress on the machine tool. Passive/dynamic vibration damping technology makes it possible to accomplish certain applications, such as some uses of tool lengths of up to 10 times bar diameter, which would not otherwise be possible even at minimal machining parameters.
Source: machining news.