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Boring bar with integrated particle damping
Additive manufacturing enables optimum vibration amplitude
Description of the component:
As part of a feasibility study, scientists from the Chair of Environmentally Compatible Production Technology at the University of Bayreuth developed an additively manufactured drill rod. Various simulation methods such as the discrete and finite element method were used for this. The innovative drill rod was manufactured from tool steel 1.2709 using laser beam melting (LBM).
Challenges:
For the internal machining of workpieces with limited space using turning, tools, including boring bars, with the highest possible length-to-diameter ratio are required. This is the only way to machine long internal geometries with a small diameter. However, an increasing length-to-diameter ratio with a constant metal removal rate leads to high vibration amplitudes of the tool (so-called chatter vibrations) and thus to a shortening of the tool life and a reduction in the surface quality of the manufactured components. The aim of the development is to reduce the vibration amplitude of the boring bar and thus extend the tool life and increase the surface quality of the manufactured components.
Solution:
The vibration amplitude of a component is influenced by three factors: mass, stiffness and damping. To achieve the lowest possible vibration amplitude, the mass must be minimized and the stiffness and damping must be maximized. A reduction in mass with comparable stiffness was achieved through a structurally optimized design inside the boring bar. Damping was also increased by integrating a particle damper. In addition to optimizing the vibration behaviour, two cooling lubricant feeds were integrated. The structurally optimized design inside the boring bar in conjunction with a particle damper and the integrated cooling lubricant supply systems can only be produced using additive manufacturing due to the manufacturing restrictions of subtractive and formative manufacturing processes.
Conclusion:
The combination of structural optimization and particle damping made it possible to reduce the vibration amplitude of the boring bar. This enables a higher length-to-diameter ratio while maintaining the tool life and surface quality of the manufactured components. As a result, internal geometries can be machined to long lengths even with small diameters. Furthermore, the cooling capacity has been increased by a near-contour cooling channel guide. This combination can only be realized using additive manufacturing.