{"id":9420,"date":"2024-12-19T09:19:33","date_gmt":"2024-12-19T09:19:33","guid":{"rendered":"https:\/\/gaspariutensili.it\/uncategorized\/anti-vibration-bars\/"},"modified":"2025-03-18T16:15:58","modified_gmt":"2025-03-18T16:15:58","slug":"anti-vibration-bars","status":"publish","type":"post","link":"https:\/\/gaspariutensili.it\/en\/technical-articles\/anti-vibration-bars\/","title":{"rendered":"Vibration dampening bars"},"content":{"rendered":"\t\t
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the vibration<\/h2>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/section>\n\t\t\t\t
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The effect of vibrations on the machining finish<\/figcaption>\n\t\t\t\t\t\t\t\t\t\t<\/figure>\n\t\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t
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The term vibration refers to a mechanical oscillation around an equilibrium point. Vibrations are an undesirable phenomenon in mechanics; in fact, they cause energy dispersion and create unwanted sounds and noises. Vibration can also cause damage to the tool used, the machinery and the workpiece.
The generation of noise and vibration is determined by three main aspects:<\/p>\n

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  1. the fixture of the piece on the machine tool<\/li>\n
  2. the geometry of the tool<\/li>\n
  3. the machining strategy and tool path<\/li>\n<\/ol>\n\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/section>\n\t\t\t\t
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    VIBRATION CONTROL<\/h2>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/section>\n\t\t\t\t
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    The basic approach to vibration control in machining is to increase the stiffness of system elements. To limit unwanted movements, the machine tool must be built with rigid and heavy structural elements, reinforced with concrete or other material that absorbs vibrations such as cast iron. Machine bearings and bushings must have close tolerances and be robust.<\/p>\n

    To maximize rigidity, a boring or turning bar should be as short as possible, but long enough to access the depth of the hole or component. The diameter of the boring bar should be as large as allowed by the diameter of the hole, while still allowing efficient ‘evacuation of chips.<\/p>\n

    As the chips form and break, the cutting forces increase and decrease.\nThese variations become a source of vibrations, which in turn can create a resonance on the natural frequency of the tool holder or machine, thus becoming self-powered or even increasing.\nOther sources of vibration are worn tools or tools that do not make a deep enough pass.\nThese cause process instability or resonance at the same natural frequency as the spindle or tool generating unwanted vibrations. <\/p>\n

    A long boring bar or a large overhang of the turning bar can cause vibrations in the machine. The basic approach to vibration control involves the use of short, rigid tools. The greater the ratio of bar length to diameter, the greater the possibility of vibrations occurring.<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/section>\n\t\t\t\t

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    THE CHALLENGE OF CHANGING THE VIBRATION FREQUENCY<\/h2>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/section>\n\t\t\t\t
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    • Changing the protrusion of an anti-vibration bar by a length equal to one time the diameter will decrease the vibration frequency by about 30 percent.<\/li>\n
    • The vibration frequency changes significantly as the ratio of exposed length to diameter changes.<\/li>\n
    • The real situation is much more complex in that the structure of the machine also affects the vibration frequency.<\/li>\n<\/ul>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/section>\n\t\t\t\t
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      THE VARIOUS TYPES OF ANTI-VIBRATION BARS<\/h2>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/section>\n\t\t\t\t
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      The different materials of the bars offer different behavior. Steel bars are generally vibration resistant up to a 4: 1 bar ratio (length: diameter). Heavy metal bars, made from tungsten alloys, are denser than steel and can handle L:D ratios up to 6:1. Solid carbide bars offer increased stiffness and allow L: D ratios up to 8: 1. The latter type of bars, however, has the disadvantage of a high cost, especially on large bars.<\/p>\n

      An alternative way to tackle the vibration problem is to use an adjustable damping bar. This tool features an internal resonant mass damper designed to resonate out of phase with respect to unwanted vibration, absorb energy, and minimize vibration amplitude. MAQ AB’s STMD\u00ae system, for example, features a self-adjusting vibration damper consisting of a mass of high-density material suspended inside the toolholder bar via asso-radial damping elements. The mass damper immediately absorbs the vibration when it is transmitted from the cutting tool to the bar body. <\/p>\n

      An active vibration control, more complex and expensive, can be represented by electronic devices capable of detecting vibrations and by secondary actuators, also electronic, to produce a vibrational motion in the tool holder to cancel the unwanted motion induced by the machining.<\/p>\n

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