Minimising vibration during machining operations has a number of advantages, including improved surface finish, reduction of scrap parts, increased cutting insert life and improved production costs.
Vibration issues are often present in machining operations where there is a high length-to-diameter ratio or if the machine tool itself is aging.
The challenge for “mass-dampened tools” is the change of the vibration frequency on machining tools due to change in the cutting conditions such as tool wear, condition of the machines moving parts, and the variation of work piece materials. For these reasons traditional mass-dampened tools require the tuning of the mass damper to optimise performance. An out-of-tune condition can make the vibration problem worse in the form of tool chatter, which is often solved by reducing cutting speed or depth of cut, or increasing feed per revolution.
The team at MAQ in Sweden studied the effects of vibration on the machining process and in 2015 developed a method of measuring a polymer’s frequency-dependent stiffness. They found that some polymers exhibited an increase in stiffness where there was an increased frequency, and it is the results of this study that were incorporated into the development of MAG’s STMD series of toolholders.
The STMD (Self Tuning Mass Dampener) series boring bars from MAQ use a different approach where the mass dampener in the toolholder body will automatically adjust its stiffness as in relation to the vibration frequency of the machine tool. Inside the tool is a tungsten mass that is completely dry; this is supported by polymer discs that react to changes in vibration and change the stiffness of the tool; this response maximises the dampening effect. STMD toolholders are designed to be “plug and play” – no tuning is required, and one holder can be used for more than one application. As the tool is self-tuning it adjusts to the vibrations that are causing tool chatter, allowing an increase in speed and feed with improved surface finish.
All MAQ vibration damped turning tools have the self-tuning mass damper technology inside and cover lengths from 3xD to 15xD. Starting from 10mm in diameter up to 60mm in diameter. Some of the boring bars in the range have an interchangeable cutter, the user can choose the cutter head to suit different insert shapes. MAQ is also developing a range of adaptors that incorporate the same self-tuning dampening technology to reduce vibration during milling operations.