Development of a practical model for selection of stable tooling system configurations in internal turning

The machining of hardened materials with hardness over 45 HRC has been an alternative to grinding since the 1970s, with the commercial availability of cubic boron nitride (cBN) and ceramic tools. However, the low toughness of these types of tool materials makes them very sensitive to damages caused by vibrations, which are critical for operations like internal turning, where the tool resembles a cantilever beam and therefore is susceptible to large deflections. This work aims to contribute to the study of tool performance in internal turning of long holes in hardened AISI 4340 steel in finishing conditions. Different machining conditions, two different tool holders (steel and carbide), and several tool overhangs were tested. The surface finish, acceleration (vibration) signals, and tool wear of cBN inserts were evaluated. The results show that vibration and the material of the tool holder may play a secondary role in the surface finish for stable turning, but the use of carbide tool holders makes the process stable for longer tool overhangs. Moreover, when the cutting becomes unstable, surface roughness is increased severely.

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“…4 (the surface aspect achieved in unstable cutting is very similar to those achieved by [15] in boring tests).…”

Section: Preliminary Testssupporting

confidence: 61%

“…Thus, to obtain a highly accurate hole, the depth of cut must be low in order to have a low radial force [14]. Cutting stability depends mainly on the L/D ratio, independent of the cutting parameters (as modeled by [15], tested in external turning with several overhangs by [16], and also in external turning by [17]). …”

Section: Introductionmentioning

confidence: 99%

Tool vibration in internal turning of hardened steel using cBN tool

Suyama

Diniz

Pederiva

2016

Int J Adv Manuf Technol

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“…Tool tip vibration corresponding to two rounds before (ux,2τ) was set to zero, for the sake of simplicity. [11] …”

Section: Cutting Force Modelmentioning

confidence: 99%

“…Main modal parameters as well as the regenerative radial force coefficient are considered as random variables. Their best guess values and probability density functions are calibrated by exploiting semi-analytical models based on the extensive experimental measurements presented in [10] and [11]. The model is finally experimentally validated, and main conclusions are drawn.…”

Section: Introductionmentioning

confidence: 99%

Robust Analysis of Stability in Internal Turning

Totis

Sortino

2014

Procedia Engineering

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When machining high precision mechanical parts, self-excited chatter vibrations must be absolutely avoided since they cause\ud unacceptable surface finish and dimensional errors. Such unstable vibrational phenomena typically arise when the overall\ud machining system stiffness is relatively low, as in the case of internal turning operations performed with slender boring bars. In\ud general, it is not easy to determine stable tooling system configurations for a given machining operation, since data available in\ud literature are often incomplete or inaccurate. In this paper, a new probabilistic algorithm for a robust analysis of stability in\ud internal turning is presented. In this approach, model parameters are considered as random variables, and robust analysis of\ud stability is carried out in order to estimate system’s probability of instability for a given boring bar geometry and material, tool\ud geometry, workpiece material and cutting parameters. By so doing, robustly stable tooling system configurations and cutting\ud conditions may be identified in the preliminary production planning phase. The proposed approach was experimentally validated\ud by considering different boring bar geometries and materials (including special boring bars made of high-damping carbide), tool\ud geometries, workpiece materials and cutting conditions. For each machining system configuration, the developed approach was\ud capable of successfully estimating the maximum ratio between boring bar overhang L and bar diameter D which assures process\ud stability for most cutting parameters combinations

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“…This phenomenon has been described in many papers, e.g. in [4 -9] From the work [8], it can be seen that cutting process stability mainly depends on the ratio of boring bar overhang L to bar external diameter D. Accordingly the critical ratio (L/D) can be defined as the maximum L/D ratio assuring process stability for most cutting parameters combinations. In this case the stability loss was found for L/D=6.…”

Section: Introductionmentioning

confidence: 97%

The influence of vibrations on surface roughness formed during precision boring

Korzeniewski

Znojkiewicz

2017

Archives of Mechanical Technology and Materials

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A B S T R A C TIn this paper, the analysis of vibrations on surface roughness generated during boring with the application of the conventional boring tool and one with the damper is presented. The experiments included the measurement of vibration accelerations carried out with the piezoelectric sensor, as well as the evaluation of surface roughness parameters after each machining pass. The obtained results reveal that in the investigated range, no stability loss was found. Furthermore, the growth of the rotational speed induces the increase of vibration level, as well as the growth of the differences between the vibration values generated during boring with the conventional tool and one equipped with damper. Vibrations have also the direct influence on the machined surface roughness. In case of the tool equipped with the damper, the tool's overhang L had more intense influence than rotational speed n. However, for the conventional boring tool this dependency was unequivocal. K E Y W O R D Svibrations, surface roughness, precision boring, finish cutting

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Development of a practical model for selection of stable tooling system configurations in internal turning

Cited by 25 publications

References 22 publications

Tool vibration in internal turning of hardened steel using cBN tool

Tool vibration in internal turning of hardened steel using cBN tool

Robust Analysis of Stability in Internal Turning

The influence of vibrations on surface roughness formed during precision boring

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