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Extending stability limits by designed-in damping

Daghini L., Archenti A., Osterlind T.

Journal of Machine Engineering

2013

Vol. 13, No. 1

37--48

With advances in material technology come challenges to productivity. New materials are, in fact, more difficult to machine with regards to tool wear and especially machine tool stability. This paper proposes to extend the stability limits of the machining system by enhancing the structures damping capability. The aim of the research work presented here is to introduce a unified concept based on the distribution of damping within the machining system components exploiting the dynamic properties of the existing joints. To maintain a high level of static stiffness, it was chosen to adapt hydrostatic clamping systems to the tools. Damping is designed in the structure via high damping interfaces (HDI), intentionally introduced interfaces where the damping ratio is enhanced by introduction of viscoelastic polymer metal composites between the two metallic surfaces composing the interface. In this paper HDI are introduced at two joints, between tool and turret and between turret and lathe. The tests show that the designed-in damping is effective and allows extending the stability limits of the machining system. The implementation of designed-in damping allows the end user to select the most suitable parameters in terms of productivity avoiding the hassle of tuning the devices, having to acquire a deep knowledge in structural dynamics or having to use additional control systems. In addition to this, the enhanced machine tool system becomes less sensitive to stability issues provoked by difficult-to-machine materials or even fluctuations of the work material properties that might occur in everyday production processes.

Cutting stability investigation on a complicated free surface machining

Lin S. Y., Chang R. W., Chung C. T., Chan C. K.

Journal of Achievements in Materials and Manufacturing Engineering

2008

Vol. 31, nr 2

531-539

Purpose: Both the results obtained previously relating to structure dynamics of a simultaneous five-axis movement machine tool and to the investigations on dynamic cutting behavior are further applied as a foundation to study the effect of the process parameters on the cutting stability in the process of a complicated free surface machining. Design/methodology/approach: In the paper cutting stability investigation on a complicated fee surface machining are described. Findings: The experimental data obtained from the cases with and without a real cutting process find that a test under a specified rotational speed can generate its own charcteristic 3-direction frequencies. The paper specially select the characteristic frequency with the most significant change on response amplitude to analyze. Practical implications: The investigation procedures and the results obtained may be used as a reference and guidance for the analysis of cutting stability in the five-axis machining of a complicated surface in industrially practical use. Originality/value: The results shown on frequency domain for identifying characteristic frequencies can be interpreted on time domain to observe amplitude variation respect to time and further understand its changing pattern under the cutting process.